//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24231 SUBJECT: LIGO/Virgo S190426c: IceCube Neutrino Search DATE: 19/04/26 16:04:02 GMT FROM: Erik Blaufuss at U. Maryland/IceCube The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search for track-like muon neutrino events consistent with the sky localization of S190426c in a time range of 1000 seconds centered on the alert event time (2019-04-26 15:13:35.337 UTC to 2019-04-26 15:30:15.337 UTC) during which IceCube was collecting good quality data. No track-like events are found in spatial coincidence with the 90% spatial containment of S190426c calculated from the map circulated in the preliminary notice. IceCube's sensitivity to point sources within the location spanned by the 90% spatial containment of S190426c ranges from 0.029 to 0.644 GeV cm^-2 in a 1000 second time window. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc@icecube.wisc.edu //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24235 SUBJECT: LIGO/Virgo S190426c: HAWC follow-up DATE: 19/04/26 16:34:47 GMT FROM: Hugo Ayala at Pennsylvania State University The HAWC Collaboration (https://www.hawc-observatory.org) reports: The HAWC Collaboration performed a follow-up of the gravitational wave trigger S190426c. At the time of the trigger, the HAWC local zenith was oriented towards (RA, Dec) = (347.3 deg, 18.9 deg). 28% of the GW candidate sky location probability fell within our observable field of view (0-45 deg zenith angle). We performed a search for a short timescale emission using 6 sliding time windows (dt = 0.3s, 1s, 3s, 10s, 30s and 100s), shifted forward in time by 20% of their width. We searched the 95% probability containment area in a timescale-dependent time period, from t0-5dt to t0+10dt, where t0 is the time of the GW trigger. No significant gamma-ray detection above the background was observed. The sensitivity of this analysis is greatly dependent on zenith angle, ranging from 33.8 deg to 45.0 deg for the area searched in this analysis. The 5sigma detection sensitivity to a 1s (100s) burst in the 80-800GeV energy range goes from 1.2e-05 erg/cm^2 to 1.1e-04 erg/cm^2 (5.7e-05 erg/cm^2 to 5.0e-04 erg/cm^2), depending on the zenith angle. HAWC is a TeV gamma-ray water Cherenkov array located in the state of Puebla, Mexico. It is sensitive to the energy range ~0.1-100TeV, and monitors 2/3 of the sky every day with an instantaneous field-of-view of ~2 sr. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24236 SUBJECT: LIGO/Virgo S190426c Global MASTER-Net observations report DATE: 19/04/26 16:39:46 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, D.Kuvshinov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.V.Chazov, D. Vlasenko Lomonosov Moscow State University, Sternberg Astronomical Institute, Moscow State University A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory K. Ivanov, O. Gres, N.M. Budnev, S. Yazev, O. Chuvalaev, V. Poleshchuk Irkutsk State University V. Yurkov, A. Gabovich, Yu. Sergienko Blagoveschensk Educational State University, Blagoveschensk R. Podesta, Carlos Lopez and F. Podesta Observatorio Astronomico Felix Aguilar (OAFA) Hugo Levato and Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias D. Buckley, S. Potter, A. Kniazev, M. Kotze South African Astronomical Observatory MASTER-Amur robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Blagoveshchensk State Pedagogical University) started inspect of the LIGO/Virgo S190426c errorbox 3232 sec after trigger time at 2019-04-26 16:15:47 UT, with upper limit up to 18.4 mag. The observations began at zenit distance = 117 deg. The sun altitude is -25.7 deg. MASTER-Tunka robotic telescope located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the LIGO/Virgo S190426c errorbox 3803 sec after trigger time at 2019-04-26 16:25:18 UT, with upper limit up to 19.5 mag. The observations began at zenit distance = 125 deg. The sun altitude is -24.9 deg. The galactic latitude b = -60 deg., longitude l = 98 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/ligo_1.php?id=10199 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 3323 | 2019-04-26 16:15:47 | MASTER-Amur | ( 2h 50m 29.91s , +85d 53m 31.28s) | C | 180 | 18.3 | 3556 | 2019-04-26 16:19:40 | MASTER-Amur | ( 14h 14m 37.41s , +85d 56m 38.95s) | C | 180 | 18.1 | 3768 | 2019-04-26 16:23:13 | MASTER-Amur | ( 0h 25m 31.78s , +85d 27m 16.37s) | C | 180 | 18.4 | 3893 | 2019-04-26 16:25:18 | MASTER-Tunka | ( 22h 27m 30.53s , +83d 55m 49.49s) | C | 180 | 19.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24237 SUBJECT: LIGO/Virgo S190426c: Identification of a GW compact binary merger candidate DATE: 19/04/26 16:45:04 GMT FROM: Deep Chatterjee at University of Wisconsin, Milwaukee The LIGO Scientific Collaboration and the Virgo Collaboration report: We identified the compact binary merger candidate S190426c during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-04-26 15:21:55.337 UTC (GPS time: 1240327333.337). The candidate was found by the GstLAL [1], MBTAOnline [2], PyCBC Live [3], and SPIIR [4] analysis pipelines. S190426c is an event of interest because its false alarm rate, as estimated by the online analysis, is 1.9e-08 Hz, or about one in 1 year, 7 months. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S190426c The classification of the GW signal, in order of descending probability, is BNS (49%), MassGap (24%), Terrestrial (14%), NSBH (13%), or BBH (<1%). Assuming the candidate is astrophysical in origin, there is strong evidence for the lighter compact object having a mass < 3 solar masses (HasNS: >99%). Using the masses and spins inferred from the signal, there is strong evidence for matter outside the final compact object (HasRemnant: >99%). Two skymaps are available at this time and can be retrieved from the GraceDB event page: * bayestar.fits.gz, the preliminary sky localization generated by BAYESTAR [5], distributed via GCN notice about 25 minutes after the candidate, * bayestar1.fits.gz, an updated localization distributed via GCN notice about an hour after the candidate. This is the preferred skymap at this time. For the bayestar1.fits.gz skymap, the 90% credible region is 1262 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 375 +/- 108 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo Public Alerts User Guide . [1] Messick et al. PRD 95, 042001 (2017) [2] Adams et al. CQG 33, 175012 (2016) [3] Nitz et al. PRD 98, 024050 (2018) [4] Qi Chu, PhD Thesis, The University of Western Australia (2017) [5] Singer & Price PRD 93, 024013 (2016) [GCN OPS NOTE(30apr19): Per author's request, the double spacing was removed.] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24242 SUBJECT: LIGO/Virgo S190426c: INTEGRAL prompt observation DATE: 19/04/26 17:40:08 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group Antonio Martin-Carrillo (UCD, Dublin) V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland) J. Rodi (IAPS-Roma, Italy) A. Coleiro (APC, France) S. Mereghetti (INAF IASF-Milano, Italy) on behalf of the INTEGRAL multi-messenger collaboration: https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration Using combination of INTEGRAL all-sky detectors (following Savchenko et al. 2017, A&A 603, A46): SPI/ACS, IBIS/Veto, and IBIS we have performed a search for a prompt gamma-ray counterpart of S190426c (GCN 24237). At the time of the event (2019-04-26 15:21:55 UTC, hereafter T0), INTEGRAL was operating in nominal mode. The peak of the event localization probability was at an angle of 59 deg with respect to the spacecraft pointing axis. This orientation implies strongly suppressed (14% of optimal) response of ISGRI, strongly suppressed (29% of optimal) response of IBIS/Veto, and somewhat suppressed (60% of optimal) response of SPI-ACS. The background within +/-300 seconds around the event was very stable (excess variance 1.2). We have performed a search for any impulsive events in INTEGRAL SPI- ACS (as described in Savchenko et al. 2012, A&A 541A, 122S), IBIS, and IBIS/Veto data. We do not detect any significant counterparts and estimate a 3-sigma upper limit on the 75-2000 keV fluence of 1.7e-07 erg/cm^2 for a burst lasting less than 1 s with a characteristic short GRB spectrum (an exponentially cut off power law with alpha=-0.5 and Ep=600 keV) occurring at any time in the interval within 300 s around T0. For a typical long GRB spectrum (Band function with alpha=-1, beta=-2.5, and Ep=300 keV), the derived peak flux upper limit is ~1.4e-07 (4.9e-08) erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24243 SUBJECT: LIGO/Virgo S190426c: Potential host galaxies from the GLADE catalog DATE: 19/04/26 18:21:59 GMT FROM: Gergely Dalya at Eotvos U Gergely Dálya and Peter Raffai (Eotvos Univ.) reports on behalf of the GLADE team: We have found 13,960 galaxies in the GLADE catalog [1,2], within the updated 90% GW localization area (bayestar1.fits.gz, the preferred skymap) reported by the LVC in GCN 24237, and within 423 +/- 128 Mpc distance limits. The galaxies found can be accessed on the GLADE website (4 MB txt file; please note that the order of galaxies in the list only follow the ordering as the appear in GLADE): http://glade.elte.hu/O3/S190426c_GLADE_90_1sigma.txt There are 935 galaxies within the 50% GW localization area and within the same distance limits (253 kB txt file; please note that the order of galaxies in the list only follow the ordering as the appear in GLADE): http://glade.elte.hu/O3/S190426c_GLADE_50_1sigma.txt [1] Dálya, G., Galgóczi G., Dobos, L. et al., 2018 MNRAS, 479, 2374 [2] http://glade.elte.hu //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24245 SUBJECT: LIGO-Virgo S190426c: AGILE MCAL observation DATE: 19/04/26 18:52:06 GMT FROM: Martina Cardillo at INAF-IAPS M.Cardillo , G.Piano, A. Ursi (INAF/IAPS), F. Verrecchia (SSDC, and INAF/OAR), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), C. Casentini, (INAF/IAPS), F. Lucarelli, C. Pittori, (SSDC, and INAF/OAR), A. Bulgarelli, N. Parmiggiani (INAF/OAS-Bologna), M. Pilia (INAF/OA-Cagliari), F. Longo (Univ. Trieste, and INFN Trieste), report on behalf of the AGILE Team: In response to the LIGO-Virgo GW event S190426c at T0 = 2019-04-26T15:21:55.337 (UT), a preliminary analysis of the AGILE minicalorimeter (MCAL) data found no event candidates within a time interval covering +/- 100 sec from the LIGO-Virgo T0. Three-sigma upper limits (ULs) are obtained for a 1 s integration time at different celestial positions within the accessible S190426c 90% c.l. localization region (that one which includes the Celestial North Pole), from a minimum of 1.27e-6 erg cm^-2 to a maximum of 2.16e-6 erg cm^-2 (assuming as spectral model a single power law with photon index 1.5). The AGILE-MCAL detector is a CsI detector with a 4 pi FoV, sensitive in the energy range 0.4-100 MeV. Additional analysis of AGILE data is in progress. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24246 SUBJECT: LIGO/Virgo S190426c: AGILE-GRID Observations DATE: 19/04/26 20:04:13 GMT FROM: Giovanni Piano at INAF-IAPS G. Piano, M. Cardillo (INAF/IAPS), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), F. Verrecchia (SSDC, and INAF/OAR), A. Ursi, C. Casentini (INAF/IAPS), F. Lucarelli, C. Pittori (SSDC, and INAF/OAR), A. Bulgarelli, N. Parmiggiani (INAF/OAS-Bologna), M. Pilia (INAF/OA-Cagliari), F. Longo (Univ. Trieste, and INFN Trieste), report on behalf of the AGILE Team: In response to the LIGO-Virgo GW event S190426c at T0 = 2019-04-26 15:21:55.337 (UT), we performed a preliminary analysis of the AGILE Gamma-Ray Imaging Detector (GRID) at different timescales in the energy range 50 MeV - 10 GeV. At T0 the accessible LIGO/Virgo 90% c.l. localization region (LR), which includes the Celestial North Pole, was observed at off-axis angles between 10 and 70 deg. Preliminary values of 3-sigma upper limits (UL) obtained at LIGO/Virgo trigger time (T0) are: (1) from 5.5e-7 to 3.2e-6 erg cm^-2 s^-1 for an integration time of 5s starting from T0, with the GRID exposure covered nearly 75% of this part of the LR. (2) from 2.8e-7 to 1.6e-6 erg cm^-2 s^-1 for an integration time of 10s starting from T0, with the GRID exposure covered nearly 80% of this part of the LR. (3) from 3.9e-8 to 1.6e-7 erg cm^-2 s^-1 for an integration time of 100s starting from T0, with the GRID exposure covered 100% of this part of the LR. The other part of the LR (R.A. in the approximate range between 10 - 16 hr) was partly occulted by the Earth at T0, and is currently in the region not accessible by the GRID because of solar panel constraints. These measurements were obtained with AGILE observing a large portion of the sky in spinning mode. Additional analysis of AGILE data is in progress. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24247 SUBJECT: LIGO/Virgo S190426c: SAO optical observation DATE: 19/04/26 20:31:00 GMT FROM: Gu Lim at Seoul National U Gu Lim (SNU), Myungshin Im (SNU), Gregory S.H. Paek (SNU), Joonho Kim (SNU), Sungyong Hwang (SNU), Bomi Park (SNU), Sophia Kim (SNU), Changsu Choi (SNU), Hyung Mok Lee (KASI), on behalf of a larger collaboration We observed host galaxy candidates in the 90% localization area of S190426c using SNU Astronomical Observatory (SAO) 1m telescope, starting at 2019-04-26 16:27:00 UT. We covered 19 candidate hosts as listed below. No apparently bright transient has been spotted in these galaxies. NAME RA DEC 2MASS+20242545+4854496 20:24:25.452 48:54:49.662 2MASS+20382080+5932155 20:38:20.808 59:32:15.504 2MASS+20435949+5314323 20:43:59.495 53:14:32.302 2MASS+20282997+5119418 20:28:29.978 51:19:41.855 2MASS+20250165+5251250 20:25:1.655 52:51:25.099 2MASS+01300015+8211097 01:30:0.151 82:11:9.780 2MASS+20252061+6132513 20:25:20.618 61:32:51.385 2MASS+01111091+8130123 01:11:10.914 81:30:12.305 2MASS+20461177+5629408 20:46:11.770 56:29:40.830 2MASS+20210572+4858452 20:21:5.728 48:58:45.224 2MASS+20255146+5356137 20:25:51.467 53:56:13.765 2MASS+20225227+4905194 20:22:52.273 49:05:19.468 PGC2352175 20:18:7.244 49:44:43.465 2MASS+20201548+4720364 20:20:15.483 47:20:36.402 2MASS+20203838+4734038 20:20:38.386 47:34:3.882 2MASS+20532613+6326079 20:53:26.133 63:26:7.915 2MASS+20343526+5423228 20:34:35.266 54:23:22.859 2MASS+20260256+5552523 20:26:2.563 55:52:52.399 2MASS+20254165+5323347 20:25:41.653 53:23:34.778 ᐧ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24248 SUBJECT: LIGO/Virgo S190426c: Fermi GBM Observations DATE: 19/04/26 20:50:31 GMT FROM: Adam Goldstein at Fermi-GBM, USRA C. Fletcher (USRA) reports on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group: For S190426c, and using the updated BAYESTAR skymap, Fermi-GBM was observing 100% of the localization probability at event time. There was no Fermi-GBM onboard trigger around the event time of the LIGO/Virgo detection of GW trigger S190426c (GCN 24237). An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM also identified no counterpart candidates. The GBM targeted search, the most sensitive, coherent search for GRB-like signals, was run from +/-30 s around merger time, and also identified no counterpart candidates. We therefore set upper limits on impulsive gamma-ray emission. Using the representative soft, normal, and hard GRB-like spectral templates described in arXiv:1612.02395, we set the following 3 sigma flux upper limits over 10-1000 keV (in units of 10^-7 erg/s/cm^2): Timescale Soft Normal Hard ------------------------------------ 0.1 s: 3.9-7.0 8.3-12. 26.-30. 1.0 s: 1.2-2.2 2.6-3.7 7.7-8.8 10 s: 0.4-0.7 0.8-1.1 2.4-2.7 Assuming the mean luminosity distance of ~375 Mpc from the GW detection, we estimate intrinsic luminosity upper limits of (0.09-1.6)E49 erg/s for the soft template, (0.2-2.6)E49 erg/s for the normal template, and (0.9-10.6)E49 erg/s for the hard template over the 1 keV-10 MeV energy range. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24249 SUBJECT: LIGO/Virgo S190426c: Tentative Red Transient Candidate from Las Cumbres Observatory DATE: 19/04/26 21:16:24 GMT FROM: Iair Arcavi at LCOGT Iair Arcavi (Tel Aviv University), Curtis McCully (LCO), Daichi Hiramatsu (LCO/UCSB), D. Andrew Howell (LCO/UCSB), Jamison Burke (LCO/UCSB), Craig Pellegrino (LCO/UCSB) on behalf of the Las Cumbres GW Follow-up Collaboration We detect a possible transient at RA Dec 217.28296 -38.190458, which we tentatively name “Nemo”, on the outskirts of the galaxy 2MASX J14290828-3811214 (redshift 0.07478 / distance 338 Mpc; Jones et al. 2009, “The 6dF Galaxy Survey Data Release 3,” via NED). We measure a preliminary aperture magnitude of 19.74 +- 0.12 in the i-band (but host contamination is likely) in a 300s image taken on 2019-04-26 18:19:33 UT at a Las Cumbres SAAO 1m telescope. This corresponds to an absolute magnitude of -17.9 at this distance. These values are corrected for MW extinction (E(B-V) = 0.0874; Schlafly, E.F. & Finkbeiner, D.P. 2011, ApJ 737, 103). “Nemo” is not visible in g-band images taken at the same time (2019-04-26 18:13:52 UT) using a Las Cumbres SAAO 1m. The source does not appear in DSS red or blue images, though they are not as deep as our discovery image. The transient is also not visible in images taken from the Las Cumbres Observatory 2m Faulkes telescope in the i band at 16:27:54, the r band at 16:33:39 , and the g band at 16:39:24 (all on 2019-04-26; all times UT) but these images are also shallower than the discovery image. Therefore the transient nature of “Nemo” is not yet confirmed. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24250 SUBJECT: LIGO/Virgo S190426c: a possible lensed NS-NS merger DATE: 19/04/26 21:27:30 GMT FROM: Graham P Smith at U of Birmingham G. P. Smith (Birmingham), M. Bianconi (Birmingham), R. Massey (Durham), and A. Robertson (Durham) report on behalf of the Gravitationally Lensed Gravitational Wave Hunters The non-zero value of Prob_MassGap identifies S190426c (GCN24237) as a possible strongly-lensed NS-NS merger - i.e. its true redshift and luminosity distance may be larger, and true mass may be smaller than inferred by LIGO/Virgo. The rate of such detections is predicted to be ~0.01 per Earth year during O3. The putative lens could be an individual galaxy, or a group/cluster of galaxies. None of the 130 known strong-lensing clusters in the sample discussed by Smith et al. (2018) are located in the updated 90% credible sky localization released an hour after detection and stated as the currently preferred skymap in GCN24237. At the estimated luminosity distance to the source (D_L~375Mpc; GCN24237) an AT2017gfo-like counterpart would have an apparent B/V-band magnitude of AB<~24.5 within ~2 days of the LIGO/Virgo detection. This estimate (albeit redshifted in to the i-band, and time-dilated to ~4 days post-detection) is also valid if the source is strongly-lensed and actually at a redshift of z~1. We encourage colleagues to observe the sky localization of this source down to AB~25, to search for a kilonova-like counterpart, and thus explore the possibility that this source is strongly-lensed, for example by a massive galaxy or group of galaxies. Background information on the details of this circular can be found in these publications: Smith, Jauzac, Veitch, et al., 2018, MNRAS, 475, 3823 Smith, Robertson, Bianconi, Jauzac, arXiv:1902.05140 Smith, Bianconi, Jauzac, et al., 2019, MNRAS, 485, 5180 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24251 SUBJECT: LIGO/Virgo S190426c: Nemo is Unrelated DATE: 19/04/26 23:13:46 GMT FROM: Iair Arcavi at LCOGT Iair Arcavi (Tel Aviv University), Curtis McCully (LCO), Daichi Hiramatsu (LCO/UCSB), D. Andrew Howell (LCO/UCSB), Jamison Burke (LCO/UCSB), Craig Pellegrino (LCO/UCSB) on behalf of the Las Cumbres GW Follow-up Collaboration The potential transient we reported in Arcavi et al. (Nemo; GCN 24249) is visible in i-band DECam images taken on 2017-05-03 03:08:06 UT (retrieved through the NOAO Data Lab). It is therefore unrelated to the LIGO/Virgo S190426c event. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24253 SUBJECT: LIGO/Virgo S190426c: STARE2 simultaneous L-band radio observations DATE: 19/04/27 00:07:51 GMT FROM: Christopher Bochenek at California Institute of Technology C. D. Bochenek (Caltech), S. R. Kulkarni (Caltech), D. McKenna (Caltech), K. Belov (JPL), V. Ravi (Harvard, Caltech), T. Callister (Caltech) STARE2 is an all-sky instrument located at the Owens Valley Radio Observatory (OVRO) and the Goldstone Deep Space Communications Complex designed to search for fast radio transients. STARE2 is sensitive to millisecond duration bursts of radio emission above 157 kJy, for a burst at zenith. STARE2 regularly sees type IIIdm bursts from the Sun. No candidate events were found within 3 hours of the LIGO/Virgo S190426c. Observing frequency: 1280-1530 MHz Time resolution: 65.536 microseconds Maximum timescale STARE2 is sensitive to: 34 ms Frequency resolution: 122.07 kHz Dispersion measure search range: 5 pc cm^-3 - 3000 pc cm^-3 A map of our upper limit as a function of RA and DEC can be found at: http://www.astro.caltech.edu/~cbochenek/LIGO_VIRGO_S190426c_limits.png The sky at OVRO at the time of the event contains 76% of the LIGO localization region. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24255 SUBJECT: LIGO/Virgo S190426c: Swift/BAT Counterpart Search DATE: 19/04/27 01:12:18 GMT FROM: Amy Lien at GSFC S. D. Barthelmy (NASA/GSFC), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), T. Sakamoto (AGU), A. A. Breeveld (MSSL-UCL), A. P. Beardmore (U. Leicester), D. N. Burrows (PSU), S. Campana (INAF-OAB), S. B. Cenko (NASA/GSFC), G. Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V. D'Elia(ASDC), S. Emery (UCL-MSSL), P. A. Evans (U. Leicester), P. Giommi (ASI), C. Gronwall (PSU), D. Hartmann (Clemson U.), J. A. Kennea (PSU), H. A. Krimm (NSF), N. P. M. Kuin (UCL-MSSL), F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), B. Mingo (U. Leicester), J. A. Nousek (PSU), S. R. Oates (Uni. of Warwick), P. T. O'Brien (U. Leicester), J. P. Osborne (U. Leicester), C. Pagani (U. Leicester), K. L. Page (U.Leicester), M. Perri (ASDC), J. L. Racusin (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU), M. H. Siegel (PSU), G. Tagliaferri (INAF-OAB), A. Tohuvavohu (PSU), E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team: We report the search results in the BAT data within T0 +/- 100 s of the LVC event S190426c (LIGO/VIRGO Collaboration GCN Circ. 24237), where T0 is the LVC trigger time (2019-04-26T15:21:55.337 UTC). The center of the BAT field of view (FOV) at T0 is RA = 255.327 deg, DEC = -7.000 deg, ROLL = 77.470 deg. The BAT FOV (>10% partial coding) covers 5.22% of the integrated LVC localization probability, and 6.39% of the galaxy convolved probability (Evans et al. 2016). Within T0 +/- 100 s, no significant detections (signal-to-noise ratio >~ 5 sigma) are found in the BAT raw light curves with time bins of 64 ms, 1 s, and 1.6 s. Assuming an on-axis (100% coded) short GRB with a typical spectrum in the BAT energy range (i.e., a simple power-law model with a power-law index of -1.32, Lien & Sakamoto et al. 2016), the 5-sigma upper limit in the 1-s binned light curve corresponds to a flux upper limit (15-350 keV) of ~ 8.10 x 10^-8 erg/s/cm^2. No event data are available at this point. BAT retains decreased, but significant, sensitivity to rate increases for gamma-ray events outside of its FOV. About 94.56% of the integrated LVC localization probability was outside of the BAT FOV but above the Earth's limb from Swift's location, and the corresponding flux upper limits for this region are within roughly an order of magnitude higher than those within the FOV. The results of the BAT analysis are available at https://swift.gsfc.nasa.gov/results/BATbursts/team_web/S190426c/web/source.html //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24257 SUBJECT: LIGO/Virgo S190426c: Public DECam Observations DATE: 19/04/27 01:38:15 GMT FROM: Daniel Goldstein at Caltech Daniel A. Goldstein (Caltech), Igor Andreoni (Caltech), Michael Coughlin (Caltech), Mansi M. Kasliwal (Caltech), Peter E. Nugent (LBNL), Joshua S. Bloom (UC Berkeley), Keming Zhang (UC Berkeley), Shreya Anand (Caltech), Jennifer Barnes (Columbia), S. Bradley Cenko (NASA GSFC), Jeffrey Cooke (Swinburne), Jorge Martínez Palomera (UC Berkeley), Leo P. Singer (NASA GSFC), on behalf of the Global Relay of Observatories Watching Transients Happen (GROWTH) and ZTF collaborations: We are observing the ecliptic lobe and southern regions of the northern lobe of the localization region of the gravitational wave trigger S190426c (LIGO Scientific Collaboration and the Virgo Collaboration, GCN #24237) with the Victor M. Blanco 4m Telescope at Cerro Tololo Inter-American Observatory, equipped with the Dark Energy Camera (DECam). An observational tiling for the event was automatically and optimally determined and triggered using the GROWTH Target of Opportunity marshal (Coughlin et al. 2019a, Kasliwal et al. 2019b). We plan to observe 35% of the integrated probability and more than 800 square degrees with 30 second visits in r and 50 in z. Our limiting magnitudes are expected to be ~22.9 in r and ~22.4 in z, based on the DECam exposure time calculator (http://www.ctio.noao.edu/noao/sites/default/files/DECam/DECam_ETC-ARW-RCS7.xls). The data from this program are immediately public and we invite anyone interested to search the images for optical counterparts. We are searching the images in real time for optical counterpart candidates using an image subtraction pipeline written for this program. We invite anyone interested to download the images. The images are available under proposal ID 2019A-0205 from the NOAO archive (archive.noao.edu). For any questions on the data or the observations, please contact the PIs of this program, Danny Goldstein and Igor Andreoni (danny@caltech.edu, andreoni@caltech.edu). GROWTH and ZTF are worldwide collaborations comprising Caltech, USA; IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; TTU, USA; LANL USA; Tokyo Tech, Japan; IIT-B, India; IIA, India; LJMU, UK and USyd, Australia. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert filtering and follow-up co-ordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24258 SUBJECT: LIGO/Virgo S190426c: GROWTH India follow-up DATE: 19/04/27 02:37:37 GMT FROM: Varun Bhalerao at Indian Inst of Tech V. Bhalerao, H. Kumar, V. Karambelkar, K. Deshmukh, D. Saraogi (IITB), G. C. Anupama, T. Stanzin, J. Stanzin (IIA) report on behalf of the GROWTH collaboration: We followed up the localisation region of the GW candidate event S190426c with the GROWTH-India telescope. We obtained 31 r-band overlapping images covering a total area of 7.5 square degrees, with 3.9% probability of containing the GW counterpart. Exposures were 600 seconds long, and reached a typical depth of 20.5 magnitude. The field centres (given below) were chosen in coordination with ZTF and DECAM (GCN 24257) to cover the northernmost part of the sky not accessible to them. These fields contain 56 galaxies from the GLADE catalog and 5 galaxies from NED. Names and coordinates of the galaxies are also given below. We do not find any new candidate counterparts in these fields. List of observed fields: ra dec 339.545 85.979 342.692 85.247 346.500 86.345 337.500 84.882 337.500 86.345 331.364 85.979 348.750 85.613 352.059 83.784 356.250 85.613 356.786 84.882 345.000 84.516 356.538 85.247 358.336 86.028 357.188 84.150 333.750 85.613 313.533 84.081 335.769 85.247 003.214 84.882 003.000 84.516 349.615 85.247 002.812 84.150 355.909 85.979 351.562 84.150 341.250 85.613 351.000 84.516 347.727 85.979 345.938 84.150 350.357 84.882 357.000 84.516 357.353 83.784 343.929 84.882 List of galaxies from NED: 351.959 85.591 VII Zw 941 352.416 85.861 2MASX J23293953+8551387 358.336 86.028 MCG +14-01-004 313.533 84.081 UGC 11664 NED01 349.941 85.373 kkh 095 List of galaxies from GLADE: ra dec name 356.005 83.640 2MASSJ23440128+8338231 355.713 83.626 2MASSJ23425102+8337319 358.775 83.909 2MASSJ23550596+8354321 359.847 83.786 2MASSJ23592318+8347099 000.843 83.890 2MASSJ00032224+8353232 350.471 83.798 2MASSJ23215295+8347536 333.012 85.867 2MASSJ22120284+8552027 335.994 86.574 2MASSJ22235866+8634273 337.236 84.779 2MASSJ22285658+8446453 336.437 85.302 2MASSJ22254483+8518062 339.315 84.712 2MASSJ22371570+8442429 339.330 86.568 2MASSJ22371927+8634059 341.079 84.767 2MASSJ22441891+8445595 343.365 85.671 2MASSJ22532770+8540144 343.507 84.754 2MASSJ22540162+8445139 343.191 86.590 2MASSJ22524594+8635254 344.556 83.900 2MASSJ22581350+8354006 345.426 84.612 2MASSJ23014222+8436430 347.221 84.347 2MASSJ23085305+8420475 347.491 84.232 2MASSJ23095774+8413568 347.547 84.580 2MASSJ23101130+8434478 347.305 85.200 2MASSJ23091312+8512017 346.687 86.588 2MASSJ23064494+8635164 348.821 84.565 2MASSJ23151704+8433526 348.365 85.910 2MASSJ23132761+8554374 348.279 85.913 2MASSJ23130697+8554472 349.952 85.246 2MASSJ23194838+8514443 349.426 85.675 2MASSJ23174216+8540308 351.498 84.983 2MASSJ23255954+8458585 352.401 85.455 2MASSJ23293632+8527167 352.092 85.487 2MASSJ23282212+8529128 353.146 84.606 2MASSJ23323509+8436200 353.222 85.505 2MASSJ23325329+8530171 353.717 85.459 2MASSJ23345217+8527335 354.043 86.052 2MASSJ23361042+8603066 356.314 84.982 2MASSJ23451539+8458560 356.520 85.413 2MASSJ23460476+8524454 356.634 86.255 2MASSJ23463222+8615196 357.738 85.186 2MASSJ23505702+8511090 357.681 85.643 2MASSJ23504338+8538359 358.058 86.274 2MASSJ23521403+8616272 358.615 84.161 2MASSJ23542759+8409392 358.618 84.422 2MASSJ23542829+8425182 358.486 84.423 2MASSJ23535669+8425237 359.447 85.001 2MASSJ23574733+8500029 000.425 84.862 2MASSJ00014210+8451427 000.209 85.273 2MASSJ00005020+8516227 001.538 84.444 2MASSJ00060903+8426372 001.427 85.020 2MASSJ00054249+8501112 002.342 85.111 2MASSJ00092210+8506409 002.206 85.919 2MASSJ00084951+8555097 002.022 85.871 2MASSJ00080534+8552153 003.587 84.672 2MASSJ00142097+8440183 004.330 84.212 2MASSJ00171922+8412432 345.896 83.870 2MASSJ23033508+8352127 353.130 83.854 2MASSJ23323111+8351147 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24259 SUBJECT: LIGO/Virgo S190426c: MAXI/GSC Observations DATE: 19/04/27 04:15:07 GMT FROM: Satoshi Sugita at Aoyama Gakuin U. S. Sugita, M. Serino (AGU), M. Sugizaki, N. Kawai (Tokyo Tech), H. Negoro (Nihon U.), M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi (Nihon U.), S. Nakahira, T. Mihara, T. Tamagawa, M. Matsuoka (RIKEN), T. Sakamoto, H. Nishida, A. Yoshida (AGU), Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, T. Sato (Chuo U.), M. Shidatsu (Ehime U.), M. Oeda, K. Shiraishi (Tokyo Tech), S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N. Isobe, R. Shimomukai, M. Tominaga (JAXA), Y. Ueda, A. Tanimoto, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake (Kyoto U.), H. Tsunemi, T. Yoneyama, K. Asakura, S. Ide (Osaka U.), M. Yamauchi, S. Iwahori, Y. Kurihara (Miyazaki U.), T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU) report on behalf of the MAXI team: We examined the MAXI/GSC all-sky X-ray images (2-20 keV) obtained in the orbit after the LVC trigger S190426c at 2019-04-26 15:21:55.337 UTC (GCN 24237). At the trigger time of S190426c, the high-voltage of MAXI/GSC was off, and it was turned on at T0+750 sec (=T0+12.5 min). The one-orbit (92 min) scan of GSC covered 84% of the 90% credible region of the bayestar1 skymap from 15:34:25 to 16:36:43　UTC (T0+750 to T0+4488 sec). No significant new source was found in the region at the one-orbit scan. The 1-sigma averaged upper limit obtained from the scan was 18 mCrab at 4-10 keV. If you require information of X-ray flux by MAXI/GSC at specific coordinates, please contact the submitter of this circular by email. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24268 SUBJECT: LIGO/Virgo S190426c: Red and blue transients identified with DECam DATE: 19/04/27 07:52:43 GMT FROM: Igor Andreoni at Caltech Igor Andreoni (Caltech), Daniel A. Goldstein (Caltech), Michael Coughlin (Caltech), Mansi M. Kasliwal (Caltech), Peter E. Nugent (LBNL), Keming Zhang (UC Berkeley), Jorge Martnez Palomera (UC Berkeley), Shreya Anand (Caltech), Joshua S. Bloom (UC Berkeley), S. Bradley Cenko (NASA GSFC), Jeffrey Cooke (Swinburne/OzGrav), Leo P. Singer (NASA GSFC), on behalf of the Global Relay of Observatories Watching Transients Happen (GROWTH) and ZTF collaborations: We report transients identified during the imaging of the localization region of the gravitational wave trigger S190426c (LIGO Scientific Collaboration and the Virgo Collaboration, GCN #24237) with the Victor M. Blanco 4m Telescope at Cerro Tololo Inter-American Observatory, equipped with the Dark Energy Camera (DECam). The observational tiling for the event was automatically and optimally determined and triggered using the GROWTH Target of Opportunity marshal (Coughlin et al. 2019a, Kasliwal et al. 2019b). Observations were performed under NOAO proposal ID 2019A-0205 (PIs Andreoni & Goldstein) and are publicly accessible (Goldstein et al., GCN 24257). Data are being processed in real time with an image-subtraction pipeline developed specifically for this program. References are taken from the Dark Energy Survey DR1 (https://www.darkenergysurvey.org/the-des-project/data-access/) and DECaLS DR6 & DR7 (http://legacysurvey.org/). The pipeline uses autoscan (Goldstein et al. 2015) to aid the rejection of spurious sources. The following criteria were adopted to select the candidates reported here. The candidates were detected at least twice and were automatically identified in images taken in both r and z filters. Photometric data points were separated at least by 30 minutes to reject moving objects. In a first table we report red sources, with r-z > 0.5 magnitude. The photometry measurements are preliminary. name | ra | dec | filter | magpsf | sigmamagpsf | filter | magpsf | sigmamagpsf DG19ftnb | 167.595543634942 | -4.35881059496403 | z | 20.39 | 0.08 | r | 20.65| 0.05 DG19kqxe | 163.781652700717 | -0.23762887433652 | z | 21.05 | 0.11 | r | 22.07| 0.12 DG19nmaf | 163.752330220064 | -1.4870117224704 | z | 21.60 | 0.10 | r | 22.89| 0.20 DG19ouub | 171.473293011207 | -9.488486251543 | z | 21.61 | 0.11 | r | 22.12| 0.10 DG19vkgf | 165.844308606225 | -7.91746108580108 | r | 19.88 | 0.01 | z | 19.57| 0.03 DG19zdwb | 167.296767466399 | -2.26827548599056 | z | 22.00 | 0.09 | r | 22.80| 0.11 DG19zyaf | 163.471809253725 | -1.15111319177025 | z | 21.55 | 0.09 | r | 22.66| 0.12 In a second table we report blue sources, with r-z < -0.4 magnitude. name | ra | dec | filter | magpsf | sigmamagpsf | filter | magpsf | sigmamagpsf DG19pklb | 168.658599720568 | -6.9754468556027 | z | 21.27 | 0.14 | r | 20.66 | 0.08 DG19ytre | 167.760353542608 | 0.527178183535021 | r | 20.69 | 0.03 | z | 21.29 | 0.07 The sources are not coincident with minor planets present in the Minor Planet Center or transients already reported in the Transient Name Server. The contact people for this circular are Igor Andreoni (andreoni@caltech.edu) and Danny Goldstein (danny@caltech.edu) GROWTH and ZTF are worldwide collaborations comprising Caltech, USA; IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; TTU, USA; LANL USA; Tokyo Tech, Japan; IIT-B, India; IIA, India; LJMU, UK and USyd, Australia. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert filtering and follow-up coordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019). This research draws upon DECam data as distributed by the Science Data Archive at NOAO. NOAO is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. This project used data obtained with the Dark Energy Camera (DECam), which was constructed by the Dark Energy Survey (DES) collaboration. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24271 SUBJECT: ANTARES follow-up of the GW candidate S190426c DATE: 19/04/27 08:16:06 GMT FROM: Damien Dornic at CPPM,France M. Ageron (CPPM/CNRS), B. Baret (APC/CNRS), A. Coleiro (APC/Universite Paris Diderot), M. Colomer (APC/Universite Paris Diderot)), D. Dornic (CPPM/CNRS), A. Kouchner (APC/Universite Paris Diderot), T. Pradier (IPHC/Universite de Strasbourg) report on behalf of the ANTARES Collaboration: Using on-line data from the ANTARES detector, we have performed a follow-up analysis of the recently reported LIGO/Virgo G330687/S190426c event using the 90% contour of the probability map provided by the GW interferometers at event time. The ANTARES visibility at the time of the alert, together with the 50% and 90% contours of the probability map are shown in https://www.cppm.in2p3.fr/~dornic/events_runo3/S190426c.png . Considering the location probability provided by the LIGO/Virgo collaborations, there is a 45% chance that the GW emitter was in the ANTARES **upgoing** field of view at the time of the alert. No up-going muon neutrino candidate events were recorded in the ANTARES sky during a +/- 500s time-window centered on the time (2019-04-26 15:21:55 UT) and in the 90% contour of the G330687/S190426c event. The expected number of atmospheric background events in the region visible by ANTARES is 5.6e-4 in the +/- 500s time window. An extended search during +/- 1 hour gives no up-going muon neutrino coincidence. The expected number of atmospheric background events in the region visible by ANTARES is 4.1e-3 in this larger time window. ANTARES is the largest undersea neutrino detector, installed in the Mediterranean Sea, and it is primarily sensitive to neutrinos in the TeV-PeV energy range. At 10 TeV, the median angular resolution for muon neutrinos is about 0.5 degrees. In the range 1-100 TeV ANTARES has a competitive sensitivity to this position in the sky. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24273 SUBJECT: LIGO/Virgo S190426c: Swift-XRT sources DATE: 19/04/27 09:05:40 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester), J.A. Kennea (PSU), A. Tohuvavohu (PSU), S.D. Barthelmy (NASA/GSFC), A.P. Beardmore (U. Leicester), A.A. Breeveld (UCL-MSSL), D.N. Burrows (PSU), S. Campana (INAF-OAB), S.B. Cenko (NASA/GSFC), G. Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V.D'Elia(ASDC), S.W.K. Emery (UCL-MSSL), P. Giommi (ASI), C. Gronwall (PSU), H.A. Krimm (CRESST/GSFC/USRA), N.P.M. Kuin (UCL-MSSL), A.Y. Lien (GSFC/UMBC), F.E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), J.A. Nousek (PSU), S.R. Oates (U. Warwick), P.T. O'Brien (U. Leicester), J.P. Osborne (U. Leicester), C. Pagani (U. Leicester), K.L. Page (U.Leicester), D.M. Palmer (LANL), M. Perri (ASDC), J.L. Racusin (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU), M.H. Siegel (PSU), G. Tagliaferri (INAF-OAB), E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team: Swift has performed a series of 197 observations, covering 197 separate locations within the LVC error region for the GW trigger S190426c convolved with the 2MPZ catalogue (Bilicki et al. 2014, ApJS, 210, 9), using the 'bayestar1' GW localisation map. As this is a 3D skymap, galaxy distances were taken into account in selecting which ones to observe. The observations currently span from 8.6 ks to 43 ks after the LVC trigger, and cover 21.5 sq degrees on the sky (corrected for overlaps). We have detected 3 X-ray sources, described below. Other sources that have been distributed as counterpart notices have been identified as artifacts or diffuse emission and are not described below. Source 5 is potentially interesting, as its flux is higher (at 2.1-sigma singificance) than in previous XRT observations (see http://www.swift.ac.uk/1SXPS/1SXPS%20J144850.8-400845 for the historical dataset in the 1SXPS catalogue). However, it is only 2.2" away from a know Seyfert 1 at z=0.123 (from SIMBAD), and therefore it is more likely that this is simply an unrelated flare from that source. Observations are, nonetheless encouraged. Each source is assigned a rank of 1-4 which describes how likely it is to be related to the GW trigger, with 1 being the most likely and 4 being the least likely. The ranks are described at http://www.swift.ac.uk/ranks.php. We have found: * 0 sources of rank 1 * 0 sources of rank 2 * 0 sources of rank 3 * 3 sources of rank 4 For all flux conversions and comparisons with catalogues and upper limits from other missions, we assumed a power-law spectrum with NH=3e20 cm^2, and photon index (Gamma)=1.7 RANK 4 sources ============== These are catalogued X-ray sources, showing no signs of outburst compared to previous observations, so they are not likely to be related to the GW trigger. Source 3: ============= RA: 346.9414 ( = 23h 07m 45.94s) J2000 Dec: +83.1619 ( = +83d 09' 42.8") J2000 Error: +24.9 (arcsec, radius, 90% confidence). Peak Rate: 7.1e-02 +/- 3.7e-02 ct/sec (0.3-10 keV) Peak Flux: 3.1e-12 +/- 1.6e-12 erg cm^-2 s^-1 (0.3-10 keV) Cat Source: 1RXS J230740.9+830945 in the ROSAT/RASSFSC catalogue Separation: 9.4" from the XRT source Cat Rate: 3.4e-02 +/- 8.3e-03 ct/sec Cat Flux: 9.5e-13 +/- 2.3e-13 erg cm^-2 s^-1 (0.3-10 keV) so the source is 1.3-sigma above the catalogued flux. There is no evidence for fading. NOTE: this source is NOT within 200 kpc of a GWGC or 2MPZ galaxy which is consistent (within 3-sigma) with the distance to the GW object. A SIMBAD object `1RXS J230740.9+830945' is 9.4" away. There are 2 2MASS objects within the source's 3-sigma error radius. Source 5: ============= RA: 222.2116 ( = 14h 48m 50.78s) J2000 Dec: -40.1461 ( = -40d 08' 46.0") J2000 Error: +11.5 (arcsec, radius, 90% confidence). Peak Rate: 1.6e-01 +/- 6.3e-02 ct/sec (0.3-10 keV) Peak Flux: 7.0e-12 +/- 2.7e-12 erg cm^-2 s^-1 (0.3-10 keV) Cat Source: 1SXPS J144850.8-400845 in the 1SXPS catalogue Separation: 0.8" from the XRT source Cat Rate: 3.0e-02 +/- 2.1e-03 ct/sec Cat Flux: 1.3e-12 +/- 9.0e-14 erg cm^-2 s^-1 (0.3-10 keV) so the source is 2.1-sigma above the catalogued flux. There is no evidence for fading. NOTE: this source is NOT within 200 kpc of a GWGC or 2MPZ galaxy which is consistent (within 3-sigma) with the distance to the GW object. A SIMBAD object `2MASS J14485097-4008456' is 2.2" away. There are 3 2MASS objects within the source's 3-sigma error radius. Source 6: ============= RA: 220.9883 ( = 14h 43m 57.19s) J2000 Dec: -39.1433 ( = -39d 08' 35.9") J2000 Error: +5.3 (arcsec, radius, 90% confidence). Peak Rate: 2.1e-01 +/- 5.8e-02 ct/sec (0.3-10 keV) Peak Flux: 8.9e-12 +/- 2.5e-12 erg cm^-2 s^-1 (0.3-10 keV) Cat Source: 1SXPS J144357.1-390839 in the 1SXPS catalogue Separation: 3.4" from the XRT source Cat Rate: 4.3e-01 +/- 5.5e-03 ct/sec Cat Flux: 1.9e-11 +/- 2.4e-13 erg cm^-2 s^-1 (0.3-10 keV) so the source is not above the catalogued flux. There is no evidence for fading. There is 1 GWGC or 2MPZ galaxy within 200 kpc of the source. and consistent (within 3-sigma) with the distance to the GW object. A SIMBAD object `NAME WISEA J144357.20-390840.0' is 4.3" away. There is 1 2MASS object within the source's 3-sigma error radius. This circular is an official product of the Swift team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24275 SUBJECT: LIGO/Virgo S190426c: Imaging confirmation and host spectroscopy of DG19vkgf DATE: 19/04/27 09:17:31 GMT FROM: Kishalay De at Caltech, GROWTH K. De (Caltech), L. Yan (Caltech), C. Fremling (Caltech), I. Andreoni (Caltech), D. Goldstein (Caltech) report on behalf of the ZTF and GROWTH collaborations We report on Target of Opportunity follow-up imaging and spectroscopy of the red transient DG19vkgf found in DECam imaging (Goldstein et al., GCN #24257; Andreoni et al., GCN #24268) of the localization region of S190426c (LIGO Scientific Collaboration and the Virgo Collaboration, GCN #24237). Spectra were obtained using the Double Beam Spectrograph (DBSP; Oke & Gunn 1982) on the Hale 200-inch telescope (P200) at Palomar observatory. We also obtained follow-up imaging of the source with the Wafer Scale Imager for Prime (WASP) on P200. Due to the high airmass of the observation and poor seeing, the transient is not clearly identified in the trace, but we confirm a host redshift of z = 0.04 from the host emission lines. However, the source is clearly detected in the images taken in i-band with WASP. We thank the staff of the Palomar observatory for facilitating these observations. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24276 SUBJECT: LIGO/Virgo S190426c: CALET Observations DATE: 19/04/27 10:07:20 GMT FROM: Valentin Pal'shin at AGU T. Tamura (Kanagawa U), A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu (Kanagawa U), N. Cannady, M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena) and the CALET collaboration: At the trigger time of the compact binary merger candidate S190426c, T0=2019-04-26 15:21:55.337 UTC (The LIGO Scientific Collaboration and Virgo Collaboration, GCN Circ. 24237), the high-voltage of the CALET Gamma-ray Burst Monitor (CGBM) detectors were off (from T0-19 min to T0+10 min). The CALET Calorimeter (CAL) was operating in high energy trigger mode at the trigger time of S190426c. Using the CAL data, we have searched for gamma-ray events in the 10-100 GeV band within the time interval T0 +/- 60 sec and found no candidates. The 90% upper limit of CAL is 2.5x10^-5 erg/cm2/s (10-100 GeV) when the summed LIGO-Virgo probability reaches 10%. The CAL FOV was centered at RA=183.0 deg, Dec=-50.9 deg at T0. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24277 SUBJECT: LIGO/Virgo S190426c: Updated localization from LIGO and Virgo data DATE: 19/04/27 11:27:08 GMT FROM: Deep Chatterjee at University of Wisconsin, Milwaukee The LIGO Scientific Collaboration and the Virgo Collaboration report: We have re-analyzed LIGO and Virgo data around the time of the compact binary coalescence (CBC) candidate S190426c (GCN 24237). Parameter estimation has been performed using LALInference [1] and a new sky map, lalinference.fits.gz, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S190426c/ For the lalinference.fits.gz skymap, the 90% credible region is 1131 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 377 +/- 100 Mpc (a posteriori mean +/- standard deviation). This is the preferred sky map at this time. For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo Public Alerts User Guide . [1] Veitch et al. PRD 91, 042003 (2015) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24278 SUBJECT: LIGO/Virgo S190426c: Hobby-Eberly Telescope VIRUS observations of target galaxies. DATE: 19/04/27 11:31:19 GMT FROM: J. Craig Wheeler at U.Texas Austin M. J. B. Rosell, Steven Janowiecki, Karl Gebhardt, and J. Craig Wheeler, on behalf of the LIGO Hobby-Eberly Telescope Response (LIGHETR) team, report the spectroscopic observation of the field of S190426c (GCN #24208) with the VIRUS IFU array. We sampled a prioritized list of 5 galaxies from the GLADE catalog that overlapped with the LIGO probability map and the observable pupil of the HET. The resulting data cube covers the wavelength 350 to 550 nm with a resolving power of 750. The effective limiting magnitude in the B band was 22 magnitudes. Each field is 50x50 arc seconds. We observed, in order, galaxies: 305.064514+47.343445 306.223328+56.174004 310.997894+53.242306 306.510681+55.881222 309.586700+59.537640 We note that 310.997894+53.242306 is a known AGN. We find no obvious evidence of an optical transient. A more detailed report of the results will be submitted later. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24279 SUBJECT: LIGO/Virgo S190426c: Updated localization to fix data format issue DATE: 19/04/27 11:58:27 GMT FROM: Leo Singer at GSFC The LIGO Scientific Collaboration and the Virgo Collaboration report: The updated localization for S190426c (GCN 24277), lalinference.fits, may have been unreadable due to a data format issue. We have re-uploaded the FITS file as LALInference1.fits.gz. This is the preferred sky map at this time. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24280 SUBJECT: LIGO/Virgo S190426c: Insight-HXMT/HE observation DATE: 19/04/27 13:10:14 GMT FROM: QiBin Yi at IHEP, HXMT Q.B.Yi, Q. Luo, C. Cai,S. Xiao , C. K. Li, X. B. Li, G. Li, J. Y. Liao, S. L. Xiong, C. Z. Liu, X. F. Li, Z. W. Li, Z. Chang, A. M. Zhang, Y. F. Zhang, X. F. Lu, C. L. Zou (IHEP), Y. J. Jin, Z. Zhang (THU), T. P. Li (IHEP/THU), F. J. Lu, L. M. Song, M. Wu, Y. P. Xu, S. N. Zhang (IHEP), report on behalf of the Insight-HXMT team: Insight-HXMT was taking data normally around the GW trigger time (T0=2019-04-26 15:21:55 UTC). At T0, about 100% of the LIGO localization region was covered by the Insight-HXMT without occultation by the Earth. Within T0 ± 100 s, no significant excess events (SNR > 3 sigma) are found in a search of the Insight-HXMT/HE raw light curves. Assuming the GW counterpart GRB with three typical GRB Band spectral models, two typical duration timescales(1 s, 10 s) from the peak position of the LIGO-Virgo location probability map, the 5-sigma upper-limits fluence (0.2 - 5 MeV, incident energy) are reported below: Band model 1 (alpha=-1.9, beta=-3.7, Ep=70 keV): 1s: 7.4e-07 erg cm^-2 10s: 3.9e-06 erg cm^-2 Band model 2 (alpha=-1.0, beta=-2.3, Ep=230 keV): 1s: 1.0e-06 erg cm^-2 10s: 5.6e-06 erg cm^-2 Band model 3 (alpha=-0.0, beta=-1.5, Ep=1000 keV): 1s: 9.6e-07 erg cm^-2 10s: 5.0e-06 erg cm^-2 Further analysis will be reported in the following circulars. All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 80-800 keV (record energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was fundedjointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information could be found at: http://www.hxmt.org. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24281 SUBJECT: LIGO/Virgo S190426c: Nanshan/NEXT Observation of Galaxies DATE: 19/04/27 13:52:46 GMT FROM: Dong Xu at NAOC/CAS Zi-Pei Zhu, Dong Xu, Bang-Yao Yu, Tian-Meng Zhang, Xu Zhou, Xiao-Ming Teng, Peng-Fei Liu, Xiang-Nan Guan, Yun-Fei Xu, Dong-Wei Fan, Chen-Zhou Cui, Hui-Juan Wang (NAOC), Sheng Yang (INAF-OAPd), Hai-Bin Zhao, Bin Li (PMO), Jin-Zhong Liu, Hu-Biao Niu, Jun-Hui Liu, Xuan Zhang (XAO), Ji-Rong Mao, Jin-Ming Bai (YNAO), Xing Gao (Urumqi No.1 Senior High School) report on behalf of the GWFUNC collaboration: We selected a bunch of galaxies from the GLADE catalog, which overlap with the high probability map of the LIGO GW event S190426c (GCN 24237) and are accessible to the NEXT-0.6m telescope located at Nanshan, Xinjiang, China. Due to weather constraint, we obtained ten field images with reasonable depth. Observations started at 17:19:27 UT on 2019-04-26 and ended at 18:40:06 UT on 2019-04-26, with each unfiltered exposure of 120 sec. Typical limiting depth is of ~18.5 mag. Below listed are the observed galaxies: Galaxy_name R.A. Dec. 2MASS+00304776+8259011 7.69904 +82.9837 2MASS+20242781+4900526 306.116 +49.0146 2MASS+20334424+5403120 308.434 +54.0533 2MASS+20370886+5756538 309.287 +57.9483 2MASS+20441724+8654219 311.072 +86.9061 2MASS+21044313+8719037 316.18 +87.3177 2MASS+21185927+8522535 319.747 +85.3815 2MASS+23370966+8226215 354.29 +82.4393 2MASS+23440128+8338231 356.005 +83.6398 2MASS+23542829+8425182 358.618 +84.4217 No apparent optical transients are found in the above galaxies. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24283 SUBJECT: LIGO/Virgo S190426c: Optical Wide-field Search with the Zwicky Transient Facility DATE: 19/04/27 14:30:40 GMT FROM: Mansi M. Kasliwal at Caltech/Carnegie Michael W. Coughlin (Caltech), Mansi M. Kasliwal (Caltech), Daniel A. Perley (LJMU), Ariel Goobar (OKC), Leo P. Singer (NASA GSFC), Shreya Anand (Caltech), Tomas Ahumada (UMD), Igor Andreoni (Caltech), Eric C. Bellm (UW), K. De (Caltech), R. Biswas (OKC), S. Nissanke (UvA), Dmitry Duev (Caltech), S. Bradley Cenko (NASA GSFC), D. Goldstein (Caltech), A. Ho (Caltech), V. Bhalerao (IITB), H. Kumar (IITB), V. Karambelkar (IITB), K. Deshmukh (IITB), D. Saraogi (IITB), G. C. Anupama (IIA), C. Copperwheat (LJMU), Virginia Cunningham (UMD), Shaon Ghosh (UWM), David Kaplan (UWM), Jesper Sollerman (OKC), Joshua S. Bloom (UCB), M. Bulla (OKC), Matthew Graham (Caltech), L. Yan (Caltech), C. Fremling (Caltech), Pradip Gatkine (UMD), A. Miller (Northwestern) On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations We observed the localization region of the gravitational wave trigger S190426c (GCN 24237) with the Palomar 48-inch telescope equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). A new tiling was automatically optimally determined and triggered using the GROWTH Target of Opportunity marshal (Coughlin et al. 2019a, Kasliwal et al. 2019b). We started obtaining target-of-opportunity observations in the g-band and r-band filters beginning at UT 2019-04-27 05:45. The projected enclosed probability with the original sky map was 75%. However, with the new sky map (GCN 24277, GCN 24279) and taking account into chip gaps and processing, a total of 4340 square degrees covering 55% of the enclosed probability were observed before 12-deg twilight and analyzed in real-time. Exposure length varied between 120s, 180s and 300s. We note that the area around the north celestial pole covered by our partner GROWTH-India telescope covers an additional 6% of the updated probability map, complementary to ZTF (see GCN 24258). The images were processed through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). After rejecting stellar sources (Tachibana and Miller 2018) and moving objects and applying machine learning algorithms (Mahabal et al. 2019), several high-significance transient candidates were identified by our pipeline in the area observed. Thanks to the overlap in sky maps between the two GW triggers S190426c and S190425z, we have very good constraints on past history of variability in the last few days. The only candidate with the first detection after the merger time is: ----------------------------------------------------------------------------------------------- ZTF Name | RA (deg) | DEC (deg) | Filter | Mag | Magerr | Filter| Mag | Magerr --------------+-------------+-------------+--------+-------+---------+-------+-------+--------- ZTF19aaslzfk | 308.968271 | 72.3536353 | r | 20.91 | 0.17 | g | 21.38 | 0.18 ----------------------------------------------------------------------------------------------- We caution that our upper limits in the last few days for ZTF19aaslzfk are shallower than the detection. So we cannot rule out an old, unrelated transient. The line-of-sight extinction is Ar of 1.4 mag (Schlafly et al. 2011). We note that the source is detected in all four WISE filters in the AllWISE catalog (Wright et al. 2010). Its W1-W3 colors are intermediate between galaxies and AGN relative to the color loci of Assef et al. (2018), but the clear W4 detection suggests contribution from an active galactic nucleus. Additional analysis and continued follow-up is in progress. ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan; IIT-B, India; IIA, India; LJMU, UK; TTU, USA; and USyd, Australia. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert filtering and follow-up co-ordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24284 SUBJECT: LIGO/Virgo S190426c: Infrared Wide-field Search with Palomar Gattini-IR DATE: 19/04/27 14:47:20 GMT FROM: Kishalay De at Caltech, GROWTH M. Hankins (Caltech), K. De (Caltech), M. Coughlin (Caltech), M. M. Kasliwal (Caltech), S. M. Adams (Caltech), I. Andreoni (Caltech), S. Anand (Caltech), L. Singer (NASA GSFC), T. Ahumada (UMD), A. Moore (ANU), J. Soon (ANU), M. Ashley (UNSW), T. Travouillon (ANU) report on behalf of the Palomar Gattini-IR team and the larger GROWTH (Global Relay of Observatories Watching Transients Happen) collaboration We report wide-field near-infrared follow-up observations of the localization region of the gravitational wave event S190426c (GCN #24237) by the Palomar Gattini-IR survey (Moore and Kasliwal 2019). Gattini-IR is a newly commissioned near-IR camera with a field of view of 25 square degrees mounted on a robotic 30 cm telescope at Palomar observatory. We started customized Target of Opportunity observations at UT 2019-04-27 03:31. The tiling was optimally determined and triggered using the GROWTH Target of Opportunity marshal (Coughlin et al. 2019a, Kasliwal et al. 2019b). We imaged a total of 2200 square degrees, covering 92% of the probability region of the event for 1 to 4 epochs until UT 2019-04-27 13:21. Each field visit consisted of a sequence of 8 dithers of 8 second exposures each on the field, which were processed and stacked with the Palomar Gattini-IR data reduction pipeline (De et al., in prep.). The typical limiting magnitude of each stacked epoch (64 second exposure time) was between 14.5 and 15 AB mag in J-band, and shallower than usual due to poor weather conditions. Transient vetting is ongoing and any viable counterparts will be announced. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24286 SUBJECT: LIGO/Virgo S190426c: CNEOST Optical Observations DATE: 19/04/27 15:08:03 GMT FROM: Dong Xu at NAOC/CAS Bin Li, Hai-bin Zhao (PMO), Dong Xu, Zi-pei Zhu, Bang-yao Yu, Tian-meng Zhang, Xu Zhou, Chen-zhou Cui, Hui-juan Wang (NAOC), Xue-feng Wu, Zhi-ping Jin, Tian-rui Sun, Hao Lu, Ge-tu Zhaori, Ren-quan Hong, Long-fei Hu (PMO), Xiao-feng Wang, Wen-xiong Li (THU), Li-fan Wang (PMO/TAMU), Jin-zhong Liu (XAO), Ji-rong Mao, Jin-ming Bai (YNAO) report on behalf of the CNEOST collaboration: We conducted optical imaging observations for gravitational wave alert with Chinese Near Earth Object Survey Telescope (CNEOST) at Xuyi astronomical station in Jiangsu Province, China (32.75N, 118.47E). The information of observations and preliminary results are listed below. Alert: LIGO/Virgo S190426c (GCN 24237) StartTime (UT): 2019-04-26T16:38:56.981 EndTime (UT): 2019-04-26T20:07:36.183 Skycover (Square Degree): 774.0 Telescope FoV (Square Degree):9.0 # id FoV_CentRA(Deg) FoV_CentDEC(Deg) LimiteMag3\sigma 5\sigma 10\sigma Filter 1 280.820160 85.517708 20.667 19.595 18.319 VR 2 315.430237 85.439629 - - - VR 3 349.655731 85.372475 - - - VR 4 0.272468 85.374985 20.421 19.412 18.049 VR 5 348.235748 82.581619 20.467 19.409 18.071 VR 6 326.778412 82.607399 - - - VR 7 305.197693 82.690369 - - - VR 8 283.561981 82.690361 - - - VR 9 280.820160 85.517708 20.667 19.595 18.319 VR 10 315.430237 85.439629 - - - VR 11 349.655731 85.372475 - - - VR 12 0.272468 85.374985 20.421 19.412 18.049 VR 13 348.235748 82.581619 20.467 19.409 18.071 VR 14 326.778412 82.607399 - - - VR 15 305.197693 82.690369 - - - VR 16 283.561981 82.690361 - - - VR 17 280.820160 85.517708 20.667 19.595 18.319 VR 18 315.430237 85.439629 - - - VR 19 349.655731 85.372475 - - - VR 20 0.272468 85.374985 20.421 19.412 18.049 VR 21 348.235748 82.581619 20.467 19.409 18.071 VR 22 326.778412 82.607399 - - - VR 23 305.197693 82.690369 - - - VR 24 283.561981 82.690361 - - - VR 25 319.178864 74.233849 20.685 19.654 18.534 VR 26 324.038544 77.046799 20.603 19.549 18.370 VR 27 311.633820 77.040756 20.651 19.597 18.336 VR 28 316.798065 79.851402 20.538 19.540 18.278 VR 29 332.518555 79.810440 - - - VR 30 348.177490 79.773155 - - - VR 31 348.773438 76.988274 20.251 19.286 18.005 VR 32 336.383240 77.012527 20.530 19.461 18.209 VR 33 339.602112 74.196800 20.347 19.336 18.174 VR 34 329.386444 74.234039 20.458 19.428 18.281 VR 35 319.178864 74.233849 20.685 19.654 18.534 VR 36 324.038544 77.046799 20.603 19.549 18.370 VR 37 311.633820 77.040756 20.651 19.597 18.336 VR 38 316.798065 79.851402 20.538 19.540 18.278 VR 39 332.518555 79.810440 - - - VR 40 348.177490 79.773155 - - - VR 41 348.773438 76.988274 20.251 19.286 18.005 VR 42 336.383240 77.012527 20.530 19.461 18.209 VR 43 339.602112 74.196800 20.347 19.336 18.174 VR 44 329.386444 74.234039 20.458 19.428 18.281 VR 45 319.178864 74.233849 20.685 19.654 18.534 VR 46 324.038544 77.046799 20.603 19.549 18.370 VR 47 311.633820 77.040756 20.651 19.597 18.336 VR 48 316.798065 79.851402 20.538 19.540 18.278 VR 49 332.518555 79.810440 - - - VR 50 336.383240 77.012527 20.530 19.461 18.209 VR 51 299.525238 46.251789 20.401 19.480 18.006 VR 52 311.657715 46.230133 20.250 19.320 17.684 VR 53 304.592407 43.480080 20.410 19.500 18.255 VR 54 302.534668 40.635784 20.422 19.507 17.783 VR 55 311.936005 37.808170 20.186 19.251 17.812 VR 56 301.344299 37.860779 20.372 19.498 17.506 VR 57 300.906097 35.026001 20.290 19.387 17.618 VR 58 307.813385 32.240044 20.193 19.273 18.032 VR 59 297.888336 32.272041 20.199 19.359 17.442 VR 60 302.225403 29.456776 20.353 19.436 18.201 VR 61 306.943420 26.630651 20.129 19.248 17.940 VR 62 297.592102 26.692783 20.381 19.452 17.974 VR 63 303.023682 23.862503 20.257 19.336 17.940 VR 64 297.782227 18.269867 20.261 19.334 17.345 VR 65 299.220764 15.473767 20.075 19.172 17.501 VR 66 298.443146 12.670787 19.969 19.078 17.526 VR 67 296.242340 7.066733 19.988 19.091 17.686 VR 68 314.732300 63.022617 20.353 19.402 18.339 VR 69 311.992279 57.445961 20.423 19.495 18.441 VR 70 309.506592 54.678425 20.287 19.374 18.141 VR 71 311.713623 49.022232 20.455 19.516 18.160 VR 72 303.515625 51.858234 20.357 19.434 17.994 VR 73 306.784424 57.462719 20.414 19.480 18.313 VR 74 308.590790 63.066647 20.359 19.407 18.222 VR 75 310.045654 60.261044 20.435 19.493 18.319 VR 76 314.339447 54.666424 20.478 19.538 18.500 VR 77 312.579285 51.856945 20.420 19.500 18.288 VR 78 303.160950 49.069408 20.422 19.490 18.076 VR 79 301.595581 57.451702 20.377 19.413 18.106 VR 80 302.417633 63.046188 20.313 19.381 18.075 VR 81 315.717224 60.247940 20.431 19.481 18.476 VR 82 317.155365 57.423546 20.405 19.476 18.382 VR 83 308.046173 51.860016 20.336 19.460 18.051 VR 84 307.452972 49.037590 20.331 19.418 18.011 VR 85 304.680237 54.659714 20.349 19.443 18.070 VR 86 304.424927 60.269768 20.302 19.374 18.127 VR Detailed data analysis is still in progress and any interesting transients will be reported later. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24289 SUBJECT: LIGO/Virgo S190426c: Lick/KAIT Follow-Up Observations DATE: 19/04/27 16:06:48 GMT FROM: Weikang Zheng at UC Berkeley WeiKang Zheng, Keto Zhang, Sergiy Vasylyev and Alexei V. Filippenko (UC Berkeley) report on behalf of the Lick/KAIT GW follow-up team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, observed the field of the gravitational-wave event S190426c (GCN 24237) detected by LIGO/Virgo. More than one thousand galaxies were selected from the Glade catalog V1.0 (Dalya et al., 2018, MNRAS, 479, 2374; http://aquarius.elte.hu/glade/) according to their priority score. KAIT observed 247 of them based on their priority scores and elevation visibility, with each clear-filter exposure time being 60 s. The first image was taken at 03:58:26, Apr. 27 UT, about 12.6 hours after the trigger, and the last image at 11:38:50 UT. Our typical limiting mag is 19.0. A transient was found in G1148595 (aka NGC3362), which was known as SN 2019cda. No other viable counterparts were identified and the analysis is ongoing. A full list of galaxies observed by KAIT is given below. GladeID UT(Apr. 27) RA (J2000) Dec ----------------------------------------------- G0183894 063314 11:11:53.490 -04:33:31.80 G0272256 060809 11:08:11.380 -01:37:58.30 G0395642 055233 12:11:00.490 -19:50:38.30 G0489265 040522 10:57:01.750 +02:24:28.60 G0548994 064600 11:12:59.190 -04:27:10.80 G0549630 084459 10:56:32.400 +08:44:36.20 G0553090 042510 11:03:11.040 -04:36:10.70 G0553090 080135 11:03:10.750 -04:36:10.60 G0553620 042031 11:02:58.740 +00:33:17.10 G0553620 075807 11:02:58.400 +00:33:17.00 G0553862 045632 10:49:11.720 +04:49:32.20 G0559959 090350 11:00:20.520 -07:05:55.70 G0562511 040631 10:58:31.320 +05:35:42.90 G0562677 045523 10:49:08.820 +04:51:46.80 G0565110 045414 10:48:48.930 +01:00:53.80 G0565949 090130 11:00:05.390 +01:04:42.00 G0566631 054903 11:55:27.330 -16:15:45.90 G0570385 072941 11:20:38.980 -08:36:52.50 G0572117 055741 11:07:17.360 -06:07:31.80 G0572117 080831 11:07:17.190 -06:07:32.20 G0572503 064451 11:12:47.450 -07:37:53.20 G0572760 052229 11:27:11.150 -11:15:14.60 G0573430 064341 11:12:47.060 -04:26:05.10 G0574754 044933 10:46:09.960 +04:50:34.20 G0575991 072611 11:19:32.690 -07:55:54.80 G0579510 045741 10:49:11.840 +04:53:44.80 G0580598 072022 11:18:54.000 -02:03:06.40 G0580886 085754 10:59:26.990 +04:06:52.60 G0585606 091828 11:36:28.050 -09:57:37.80 G0587735 035826 10:52:48.900 +03:40:35.60 G0587735 075328 10:52:48.950 +03:40:35.90 G0590130 062423 11:10:19.390 -00:57:29.70 G0590201 044006 10:40:04.890 +04:32:48.50 G0590201 051538 10:40:04.750 +04:32:48.60 G0590484 061357 11:08:36.810 -00:07:54.90 G0590484 082002 11:08:36.760 -00:07:54.30 G0590830 070000 11:15:38.320 -06:52:47.50 G0593995 044451 10:45:30.730 +02:15:52.80 G0594030 053141 11:40:29.620 -14:18:37.10 G0594729 052120 11:22:53.250 -10:35:01.20 G0596108 042950 11:05:19.920 -06:36:39.00 G0601147 053032 11:39:24.280 -13:11:22.80 G0606812 062314 11:10:19.570 -00:13:13.60 G0609002 052704 11:38:21.850 -13:16:55.90 G0609034 074336 11:24:39.240 -09:32:17.10 G0609179 085310 10:58:51.020 +07:56:26.20 G0609910 084938 10:57:46.520 +06:45:00.90 G0612118 052338 11:29:23.350 -11:28:41.20 G0612394 041222 11:00:13.940 -00:47:46.70 G0614729 041810 11:02:28.040 -04:22:26.50 G0614729 075546 11:02:27.830 -04:22:25.90 G0614900 063902 11:12:06.930 -06:42:07.50 G0616501 083537 10:52:57.090 -01:37:27.70 G0617323 060331 11:07:38.320 -01:35:59.60 G0617323 081306 11:07:38.250 -01:36:00.50 G0618318 041112 10:59:56.520 +01:20:00.40 G0623013 073859 11:23:26.420 -05:18:02.40 G0624899 040154 10:55:57.210 +00:20:57.30 G0626343 055850 11:07:28.740 -02:49:38.70 G0626343 080940 11:07:28.510 -02:49:38.50 G0626541 073531 11:22:03.470 -09:29:28.80 G0626921 074555 11:25:50.630 -08:54:09.50 G0628200 043526 10:34:54.430 +11:06:24.10 G0628200 051100 10:34:54.450 +11:06:24.50 G0628220 090615 11:01:12.890 -03:11:30.50 G0628851 083909 10:54:50.990 +00:14:02.00 G0632969 061725 11:08:45.040 -01:50:54.90 G0632969 082330 11:08:45.030 -01:50:54.00 G0634233 084129 10:55:43.340 +02:30:32.30 G0634535 074813 11:26:10.620 -09:08:49.70 G0635861 060113 11:07:37.230 -02:45:59.80 G0637766 060222 11:07:37.180 -02:49:25.80 G0637766 081159 11:07:37.280 -02:49:26.10 G0638543 052813 11:39:15.390 -13:31:53.00 G0638671 041442 11:01:32.170 +02:00:42.00 G0638963 073420 11:22:00.000 -04:39:50.60 G0639517 061248 11:08:31.140 +00:40:42.60 G0639517 081853 11:08:31.020 +00:40:41.70 G0640572 074445 11:24:47.290 -08:47:44.60 G0642533 060004 11:07:34.950 -00:48:14.60 G0642533 081050 11:07:35.010 -00:48:14.90 G0643033 064819 11:13:14.100 -05:51:32.60 G0643853 063423 11:11:57.340 -03:40:42.90 G0643892 045042 10:47:24.260 +07:28:55.80 G0644398 061139 11:08:28.370 +03:41:51.40 G0648171 040852 10:59:33.480 -04:26:35.90 G0648835 083316 10:52:30.000 +09:10:35.60 G0651799 073750 11:22:40.810 -04:38:37.00 G0652133 062904 11:10:55.840 -04:34:46.00 G0653686 070218 11:16:15.630 -05:25:05.10 G0655620 040303 10:56:03.430 -01:11:56.90 G0656169 090241 11:00:15.530 -03:38:13.20 G0656942 072243 11:19:28.640 -09:43:43.60 G0657266 085050 10:58:30.470 +00:41:51.90 G0657990 050915 10:52:14.890 +02:20:05.00 G0662103 042838 11:04:49.470 -00:42:22.80 G0662103 080503 11:04:49.340 -00:42:22.60 G0662104 070439 11:16:56.960 -02:16:34.90 G0662185 074227 11:24:02.990 -10:02:57.30 G0663137 085422 10:58:59.070 -03:11:54.10 G0663945 041001 10:59:38.490 -03:36:29.50 G0664356 084608 10:56:32.340 +04:21:00.90 G0666774 043855 10:39:38.940 +11:06:59.60 G0666774 051426 10:39:39.340 +11:07:00.80 G0668963 084239 10:55:58.800 +01:16:59.60 G0670041 084348 10:55:59.910 -00:52:07.50 G0670285 044340 10:44:31.400 +10:52:36.90 G0670531 050328 10:49:47.930 +04:12:16.50 G0671170 063530 11:11:59.740 -04:25:48.90 G0672325 060441 11:07:42.350 -04:50:51.60 G0672325 081416 11:07:42.330 -04:50:51.90 G0673700 050219 10:49:47.260 +04:12:49.20 G0675153 073640 11:22:37.580 -06:28:58.70 G0676039 050656 10:51:04.980 +01:41:47.50 G0676486 045151 10:47:34.530 +04:00:38.50 G0679815 040045 10:55:21.640 -00:28:06.50 G0681167 042140 11:03:02.320 +03:28:33.30 G0681402 063640 11:11:58.860 -08:08:07.40 G0681509 085644 10:59:12.510 +07:28:05.80 G0682016 061834 11:08:53.780 -05:06:34.60 G0682016 082439 11:08:53.790 -05:06:34.60 G0682408 072501 11:19:32.180 -04:30:05.20 G0682877 053251 11:40:46.570 -14:44:24.40 G0685235 062755 11:10:45.720 +00:42:30.90 G0685620 045851 10:49:24.330 +05:10:02.90 G0688162 052448 11:35:09.580 -10:50:21.50 G0688773 054207 11:43:16.740 -11:58:29.10 G0692183 055452 12:15:02.740 -18:39:13.00 G0697713 070548 11:17:12.200 -05:23:54.70 G0697935 040740 10:59:10.690 +01:30:04.50 G0698912 062532 11:10:19.430 -00:32:44.50 G0702659 053947 11:42:21.260 -17:40:25.50 G0704552 074923 11:27:34.250 -08:21:24.90 G0704844 043636 10:36:25.050 +07:26:46.50 G0704844 051209 10:36:25.120 +07:26:47.40 G0705327 054426 11:48:24.070 -16:44:03.50 G0707027 054058 11:42:30.220 -12:29:41.00 G0707360 063014 11:11:32.850 -00:41:17.40 G0711373 063751 11:11:59.750 -00:59:54.00 G0712402 071652 11:17:12.550 -06:35:08.10 G0714524 041331 11:01:19.740 -05:06:42.40 G0716604 054644 11:54:02.060 -16:29:25.20 G0716777 050109 10:49:44.020 +07:09:13.20 G0716998 044229 10:42:15.900 +04:47:08.40 G0717672 053619 11:41:58.330 -12:30:19.30 G0719909 043745 10:38:53.610 +10:39:26.70 G0719909 051319 10:38:53.630 +10:39:26.70 G0725542 035935 10:53:53.400 -00:47:07.90 G0729766 054535 11:52:35.920 -16:26:03.80 G0733916 084020 10:55:26.470 +07:02:24.10 G0734402 090724 11:01:25.540 -03:23:12.90 G0737008 042401 11:03:07.050 -03:46:44.70 G0737008 080026 11:03:06.880 -03:46:44.80 G0737866 085905 10:59:28.100 -05:47:35.20 G0738123 050547 10:51:00.990 +04:51:35.50 G0739133 075032 11:28:14.430 -06:19:19.30 G0739740 044714 10:45:50.130 +02:56:54.90 G0739801 064121 11:12:15.250 -06:22:20.70 G0740064 074704 11:26:07.180 -06:36:26.10 G0740915 064232 11:12:16.140 -00:55:46.90 G0741452 052923 11:39:21.050 -12:03:47.50 G0743465 090504 11:00:33.350 +07:34:48.40 G0743638 064012 11:12:13.590 -06:24:54.60 G0743790 083759 10:53:29.850 -00:46:10.00 G0747080 084720 10:56:59.340 -01:03:28.80 G0751074 040412 10:56:19.420 -01:02:49.80 G0754612 044603 10:45:36.770 +11:11:38.50 G0755412 043101 11:06:35.450 +00:46:22.40 G0755412 080612 11:06:35.560 +00:46:23.80 G0756145 053509 11:41:52.100 -10:49:50.90 G0756454 072133 11:19:22.100 -07:13:06.50 G0763402 084829 10:57:33.990 +03:17:43.60 G0764514 061027 11:08:16.820 -02:03:21.50 G0764514 081743 11:08:16.780 -02:03:21.30 G0765819 060550 11:07:44.430 -04:10:38.00 G0766381 052557 11:36:28.270 -12:27:08.60 G0769870 072829 11:20:25.560 -03:31:04.30 G0770090 061616 11:08:44.210 -02:20:19.00 G0770090 082221 11:08:44.150 -02:20:18.90 G0770692 042729 11:04:03.530 -04:14:39.50 G0770692 080354 11:04:03.500 -04:14:39.40 G0777282 044119 10:40:59.690 +03:00:39.80 G0777282 051647 10:40:59.810 +03:00:40.30 G0777485 060918 11:08:15.420 -02:04:25.90 G0777485 081634 11:08:15.440 -02:04:25.00 G0778169 065146 11:13:35.480 -03:19:01.10 G0779011 041552 11:01:48.900 +00:17:44.50 G0781665 054316 11:44:43.320 -13:24:11.40 G0782431 061506 11:08:41.020 -03:17:10.80 G0782431 082111 11:08:41.090 -03:17:10.50 G0782924 050805 10:51:32.370 +00:39:01.70 G0785186 074008 11:23:38.550 -10:20:51.70 G0786363 041701 11:02:21.410 -01:14:39.40 G0786363 075437 11:02:21.420 -01:14:38.70 G0786634 055124 12:10:47.060 -19:08:09.60 G0790178 062053 11:09:29.050 -03:44:26.80 G0790178 082658 11:09:28.860 -03:44:27.40 G0791742 073159 11:21:26.650 -07:28:36.70 G0792779 050437 10:50:02.100 +02:46:50.70 G0796085 065256 11:14:03.010 -03:23:20.70 G0796285 053728 11:42:06.470 -12:50:31.60 G0797419 060659 11:07:44.820 -01:13:49.00 G0797419 081525 11:07:45.030 -01:13:49.60 G0798730 053400 11:41:01.030 -12:46:37.60 G0798801 072720 11:19:35.450 -04:54:41.60 G0800890 083427 10:52:45.910 +02:48:19.50 G0804096 071802 11:17:47.010 -08:22:50.80 G0805699 071913 11:17:58.550 -01:20:35.20 G0806101 045302 10:47:39.970 +11:39:46.30 G0807574 083648 10:53:08.290 +04:57:22.10 G0810723 065850 11:15:38.120 -05:24:44.00 G0811304 053835 11:42:17.440 -12:49:54.30 G0815282 090018 10:59:59.410 +06:25:06.40 G0822175 055631 11:06:37.290 -03:30:16.00 G0822175 080722 11:06:37.450 -03:30:14.20 G0822865 085533 10:59:05.490 +02:17:08.60 G0823787 085201 10:58:31.270 +06:33:23.10 G0845933 065741 11:15:30.800 -05:33:26.30 G0867712 091938 11:38:50.060 -09:28:51.20 G0915032 055012 12:00:03.340 -17:08:02.60 G0932849 055342 12:14:16.220 -19:20:41.40 G0958433 073308 11:21:39.860 -09:57:45.50 G0965443 064709 11:12:59.870 -06:50:25.90 G0979304 041922 11:02:38.370 +01:18:33.20 G0979304 075658 11:02:38.200 +01:18:33.40 G1032288 061944 11:09:16.340 -05:14:13.40 G1032288 082549 11:09:16.330 -05:14:13.00 G1052029 065521 11:14:36.820 -02:03:39.60 G1070206 070109 11:15:41.100 -03:55:12.30 G1086865 065632 11:15:11.260 -07:00:17.20 G1126327 070328 11:16:55.520 -07:23:22.60 G1148595 044823 10:45:51.860 +06:29:41.60 G1276417 072352 11:19:29.230 -06:28:55.00 G1278481 073050 11:20:50.830 -04:36:27.80 G1279248 074118 11:23:52.390 -09:07:42.10 G1342028 054754 11:54:24.840 -16:03:20.80 G1377676 075141 11:28:44.080 -06:55:21.00 G1420214 062202 11:09:54.380 -06:17:49.50 G1437959 065037 11:13:29.430 -06:04:50.20 G1640464 042620 11:03:13.500 -01:12:28.10 G1640464 080244 11:03:13.420 -01:12:28.10 G1642067 050000 10:49:42.600 +04:11:20.10 G1642147 065411 11:14:19.640 +02:26:29.00 G1642887 042251 11:03:03.470 -02:33:25.10 G1642887 075917 11:03:03.390 -02:33:26.10 G1645440 064928 11:13:22.450 -03:18:12.90 G1667542 062642 11:10:34.290 -03:46:19.10 [GCN OPS NOTE(27apr19): Per author's request, the "observed XXX" was changed to "observed 247".] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24291 SUBJECT: LIGO/Virgo S190426c: GOTO optical coverage - no notable counterparts DATE: 19/04/27 16:20:13 GMT FROM: Danny Steeghs at U.of Warwick/GOTO D.Steeghs(1), J.Lyman(1), M.Dyer(3), D.Galloway(2), V.Dhillon(3), P.O'Brien(4), G.Ramsay(5), D.Pollacco(1), E.Thrane(2), S.Poshyachinda(6), E.Palle(7), K.Ulaczyk(1), R.Cutter(1), A.Levan(1), T. Marsh(1), R.West(1), K.Wiersema(1), B.Gompertz(1), E.Stanway(1), K.Ackley(2), A.Obradovic(2), Y-L.Mong(2), A.Casey(2), M.Brown(2), E.Rol(2), J.Mullaney(3), S.Littlefair(3), L.Makrygianni(3), E.Daw(3), J.Maund(3), R.Starling(4), R.Eyles(4), U.Sawangwit(6), D.Mkrtichian(6), S.Awiphan(6),S.Aukkaravittayapun(6), P.Irawati(6), M.Kennedy(8), R.Breton(8), D.Mata-Sanchez(8), T.Heikkila(9), R.Kotak(9) (1) Warwick University; (2) Monash University; (3) Univ. of Sheffield; (4) University of Leicester; (5) Armagh Observatory; (6) National Astronomical Research Institute of Thailand; (7) Instituto de Astrofisica de Canarias; (8) Univ. of Manchester; (9) University of Turku report on behalf of the GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer in response to event S190426c (GCN #24237). Targeted observations across 49 pointings containing 54.1% of the source location probability across 755 sqr. degrees (based on the updated LALInference skymap, GCN #24279) were performed between 20:38 UT Apr 26 and 05:32 UT Apr 27 2019. A small number of fields were affected by having limited quality survey reference frames available and the area includes dense low galactic latitude fields. We recover a number of known/already reported transients and many foreground variable objects, but no significant detections of new candidates that could be credibly associated with S190426c. Each pointing spans 4.9x3.7 square degrees and consisted of 3x60s exposures in our L-band filter (400-700nm passband) with typical 5-sigma photometric depth of g=19.9, based on a photometric calibration against PS1 sources. A coverage map is available at http://goto-observatory.warwick.ac.uk/S190426c.html Images are processed immediately after acquisition using the GOTOphoto pipeline. Difference imaging was performed on the median of each triplet of exposures using recent survey observations of the same pointings. Source candidates were initially filtered using a classifier and cross-matched against a variety of catalogs, including the MPC and PS1. Human candidate vetting was performed during data acquisition and processing in case of notable detections. GOTO is operated at the La Palma observing facilities of the University of Warwick on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT) and the Instituto de Astrofisica de Canarias (IAC) (https://goto-observatory.org/) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24292 SUBJECT: LIGO/Virgo S190426c: MMT Follow-Up Observations DATE: 19/04/27 16:25:32 GMT FROM: Griffin Hosseinzadeh at Harvard U G. Hosseinzadeh, S. Gomez, L. Patton, E. Berger, P. K. Blanchard, T. Eftekhari, J. Gill, V. A. Villar, P. K. G. Williams (Harvard U), P. S. Cowperthwaite (Carnegie Obs), R. Chornock (Ohio U), W. Fong, R. Margutti (Northwestern U), and M. Nicholl (U Edinburgh) report: We obtained 30 s i-band images of the following GLADE galaxies (Dalya et al. 2018, MNRAS, 479, 2374) in the LIGO/Virgo localization region of S190426c (GCN 24237) with the MMTCam instrument on the MMT 6.5-m telescope: Name R.A. Dec. Date UT 18191810+8807285 274.825439 88.124603 2019-04-27 08:38:51.40 18215068+8642223 275.461182 86.706215 2019-04-27 08:40:44.16 18242867+8642139 276.119476 86.703888 2019-04-27 08:42:02.29 19301513+8540516 292.563049 85.681000 2019-04-27 08:44:01.04 20412914+8626330 310.371429 86.442513 2019-04-27 08:47:15.62 20441724+8654219 311.071838 86.906105 2019-04-27 08:48:44.73 3085923 313.123840 86.186646 2019-04-27 08:50:06.79 20452666+8620428 311.361084 86.345238 2019-04-27 08:53:22.23 20592695+8454369 314.862305 84.910271 2019-04-27 08:55:00.27 20110295+4637149 302.762329 46.620808 2019-04-27 09:00:55.59 20113931+4550035 302.913818 45.834320 2019-04-27 09:03:02.52 20114858+4657335 302.952423 46.959324 2019-04-27 09:04:39.00 20132761+4630313 303.365082 46.508705 2019-04-27 09:06:17.34 20134502+4726333 303.437622 47.442604 2019-04-27 09:07:51.07 20152058+4555282 303.835785 45.924526 2019-04-27 09:09:30.54 20201548+4720364 305.064514 47.343445 2019-04-27 09:12:40.37 20242781+4900526 306.115875 49.014629 2019-04-27 09:14:19.34 20354336+4953165 308.930695 49.887932 2019-04-27 09:15:46.70 20224302+5636145 305.679291 56.604050 2019-04-27 09:17:53.43 20244336+5245430 306.180695 52.761951 2019-04-27 09:19:32.34 20245359+5610264 306.223328 56.174004 2019-04-27 09:20:53.09 20260256+5552523 306.510681 55.881222 2019-04-27 09:22:19.39 20273404+5015483 306.891846 50.263424 2019-04-27 09:23:52.13 20273859+5353393 306.910797 53.894264 2019-04-27 09:25:23.97 20281516+5641284 307.063202 56.691227 2019-04-27 09:26:51.40 20290191+5817016 307.257996 58.283779 2019-04-27 09:28:13.83 20291160+5219510 307.298340 52.330837 2019-04-27 09:29:55.67 20300804+5415120 307.533508 54.253361 2019-04-27 09:31:48.43 20304675+6259395 307.694824 62.994316 2019-04-27 09:37:44.30 20322187+5812031 308.091156 58.200874 2019-04-27 09:39:26.33 20334424+5403120 308.434357 54.053345 2019-04-27 09:41:06.11 20334533+6254178 308.438904 62.904968 2019-04-27 09:42:45.02 20352447+5759548 308.851959 57.998581 2019-04-27 09:44:34.03 20354995+6208172 308.958160 62.138115 2019-04-27 09:47:16.72 20355212+5549587 308.967194 55.832996 2019-04-27 09:49:52.60 20370886+5756538 309.286957 57.948280 2019-04-27 09:51:23.64 20373532+5628217 309.397186 56.472702 2019-04-27 09:52:50.88 20384775+6128473 309.698975 61.479832 2019-04-27 09:54:43.33 20385946+5351220 309.747772 53.856125 2019-04-27 09:56:30.10 20391360+6454369 309.806671 64.910263 2019-04-27 09:58:12.37 20404068+6437003 310.169525 64.616753 2019-04-27 09:59:56.03 20431546+5424171 310.814453 54.404751 2019-04-27 10:02:35.77 20450027+6441410 311.251160 64.694733 2019-04-27 10:04:16.29 20452857+6332249 311.369080 63.540272 2019-04-27 10:05:41.40 20453196+6157519 311.383179 61.964432 2019-04-27 10:07:11.51 20482612+6414178 312.108856 64.238281 2019-04-27 10:08:31.27 20492307+6412331 312.346161 64.209221 2019-04-27 10:10:38.44 20495907+6207478 312.496155 62.129963 2019-04-27 10:12:07.42 20515127+6309235 312.963654 63.156536 2019-04-27 10:13:43.40 20581565+6217178 314.565247 62.288288 2019-04-27 10:15:27.92 Comparison of the images to the PS1 3pi survey (Chambers et al. 2016, arXiv:1612.05560) reveals no new sources brighter than ~21 mag within the 2.7 arcmin field of view. We thank Chun Ly and Ben Kunk at MMT for taking these observations and Dallan Porter for help with the target submission. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24298 SUBJECT: LIGO/Virgo S190426c: COATLI Optical Observations of Galaxies DATE: 19/04/27 19:18:40 GMT FROM: Alan M Watson at UNAM Rosa L. Becerra (UNAM), Alan M. Watson (UNAM), Nat Butler (ASU), Eleonora Troja (GSFC/UMD), Simone Dichiara (UMD), Diego González (UNAM), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Margarita Pereyra (UNAM), and Tanner Wolfram (ASU) report: We observed 98 galaxies selected from the NED/CLU list for LIGO/Virgo S190426c (Chatterjee et al, GCN Circ. 24237) with the COATLI 50-cm telescope and interim imager at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir (http://coatli.astroscu.unam.mx) on the night of 2019-04-27 UTC. For each galaxy, we typically obtained 150 seconds of exposure in the w filter and obtained a typical 10-sigma limiting magnitude of 19.5. Our observations are listed below. Visual inspection reveals no obvious counterpart candidates. We thank the COATLI technical team and the staff of the Observatorio Astronómico Nacional. Start (UTC) 00 0RA and Dec (J2000) Galaxy 2019-04-27 03:38 352.4159 +85.8608 2MASX J23293953+8551387 2019-04-27 03:42 359.6944 +83.1832 MCG +14-01-005 2019-04-27 03:46 344.9978 +88.5296 2MASX J22595902+8831466 2019-04-27 03:50 274.8875 +87.6408 2MASX J18193355+8738264 2019-04-27 03:59 272.7131 +87.6117 2MASX J18105107+8736422 2019-04-27 04:05 263.4949 +88.3113 MCG +15-01-018 2019-04-27 04:13 358.3364 +86.0277 MCG +14-01-004 2019-04-27 04:16 334.1561 +86.9297 2MASX J22163720+8655469 2019-04-27 04:20 346.0840 +86.7498 UGC 12387 2019-04-27 04:24 314.1693 +87.8807 VII Zw 938 2019-04-27 04:28 308.7320 +87.8154 2MASX J20345612+8748562 2019-04-27 04:31 345.8574 +86.7660 UGC 12377 2019-04-27 04:57 275.8067 +86.8905 UGC 11339 2019-04-27 05:02 350.3873 +83.0117 2MASX J23213266+8300409 2019-04-27 05:05 008.0015 +83.2104 2MASX J00320030+8312372 2019-04-27 05:09 012.1694 +83.7556 UGC 00481 2019-04-27 05:12 008.9427 +83.2329 2MASX J00354608+8313586 2019-04-27 05:16 313.5333 +84.0810 UGC 11664 NED01 2019-04-27 05:19 260.0731 +86.7364 UGC 10923 NED02 2019-04-27 06:39 271.6471 +87.8094 UGC 11267 2019-04-27 06:44 268.8382 +87.7292 MCG +15-01-020 2019-04-27 06:48 266.3379 +87.6423 CGCG 370-007 2019-04-27 06:52 259.8809 +86.7384 UGC 10923 NED01 2019-04-27 06:56 343.4309 +81.7412 2MASX J22534338+8144284 2019-04-27 07:00 265.9047 +86.4693 2MASX J17433725+8628095 2019-04-27 07:04 018.9765 +85.1649 CGCG 360-004 2019-04-27 07:07 304.6286 +62.2037 2MASX J20183085+6212133 2019-04-27 07:14 169.1621 -05.6357 LCRS B111406.3-052146 2019-04-27 07:17 306.9895 +62.5326 2MASX J20275744+6231575 2019-04-27 07:21 304.8255 +58.3678 2MASX J20191811+5822039 2019-04-27 07:24 304.2367 +57.0611 2MASX J20165680+5703397 2019-04-27 07:28 305.1467 +56.2499 CGCG 282-003 2019-04-27 07:31 306.7128 +57.3910 2MASX J20265107+5723277 2019-04-27 07:34 309.2900 +60.3766 2MASX J20370963+6022358 2019-04-27 07:38 309.0248 +58.3807 2MASX J20360594+5822504 2019-04-27 07:41 310.0597 +59.5819 2MASX J20401431+5934550 2019-04-27 07:48 309.4146 +57.3066 2MASX J20373949+5718234 2019-04-27 07:51 311.9760 +57.5972 2MASX J20475419+5735501 2019-04-27 07:55 311.7825 +57.5936 4C +57.35 2019-04-27 07:58 312.1427 +57.0269 2MASX J20483420+5701370 2019-04-27 08:01 312.8025 +57.4421 2MASX J20511259+5726315 2019-04-27 08:05 311.4040 +57.5578 2MASX J20453697+5733282 2019-04-27 08:08 312.2525 +57.6652 2MASX J20490061+5739550 2019-04-27 08:11 304.9635 +48.2723 2MASX J20195124+4816205 2019-04-27 08:15 308.2331 +54.5088 UGC 11592 2019-04-27 08:22 309.9248 +59.5971 2MASX J20394194+5935495 2019-04-27 08:26 299.3077 +19.0874 2MASX J19571383+1905142 2019-04-27 08:29 309.7008 +60.6565 2MASX J20384818+6039233 2019-04-27 08:33 301.0079 +19.2880 2MASX J20040188+1917170 2019-04-27 08:36 301.1253 +19.4085 2MASX J20043008+1924304 2019-04-27 08:40 319.1351 +64.0099 2MASX J21163245+6400358 2019-04-27 08:43 309.3741 +61.0047 2MASX J20372983+6100169 2019-04-27 08:47 304.1979 +56.4738 2MASX J20164753+5628258 2019-04-27 08:50 300.7020 +22.4744 V0362 Vul 2019-04-27 08:57 303.7470 +25.3836 2MASX J20145928+2523010 2019-04-27 09:00 308.8950 +55.9269 2MASX J20353480+5555368 2019-04-27 09:04 299.2132 +16.5608 2MASX J19565118+1633389 2019-04-27 09:07 306.7007 +56.5190 2MASX J20264814+5631084 2019-04-27 09:10 311.3915 +57.0962 2MASX J20453392+5705462 2019-04-27 09:14 305.3853 +49.7603 2MASX J20213251+4945372 2019-04-27 09:17 298.8340 +18.3959 2MFGC 15201 2019-04-27 09:21 314.8096 +58.6364 2MASX J20591430+5838107 2019-04-27 09:24 309.0573 +63.7399 UGC 11603 2019-04-27 09:30 308.8765 +59.2313 2MASX J20353036+5913528 2019-04-27 09:35 314.7172 +57.6427 2MASX J20585215+5738335 2019-04-27 09:39 309.3163 +59.8381 2MASX J20371593+5950168 2019-04-27 09:44 303.4031 +64.4171 2MASX J20133671+6425013 2019-04-27 09:48 304.1438 +26.9762 2MASX J20163450+2658344 2019-04-27 09:51 304.6728 +59.4700 MCG +10-29-002 2019-04-27 09:55 301.6173 +18.5862 2MFGC 15313 2019-04-27 09:58 300.9117 +21.5433 2MASX J20033878+2132359 2019-04-27 10:04 310.3060 +63.5107 UGC 11616 2019-04-27 10:09 313.9236 +69.7426 2MASX J20554160+6944333 2019-04-27 10:12 305.4690 +57.5173 2MASX J20215255+5731021 2019-04-27 10:17 302.5725 +48.0059 2MASX J20101740+4800214 2019-04-27 10:21 304.1962 +25.6489 2MASX J20164708+2538564 2019-04-27 10:24 305.1636 +49.7551 2MFGC 15467 2019-04-27 10:28 303.7108 +63.5932 2MASX J20145058+6335356 2019-04-27 10:31 310.9155 +57.6082 2MASX J20433966+5736291 2019-04-27 10:37 313.2613 +66.4034 VII Zw 937 2019-04-27 10:41 308.1690 +60.0050 2MASX J20324060+6000181 2019-04-27 10:44 253.3640 +86.5912 UGC 10740 2019-04-27 10:48 304.1095 +50.2973 2MASX J20162627+5017501 2019-04-27 10:52 303.8571 +60.4465 2MASX J20152569+6026477 2019-04-27 10:55 303.3392 +63.0623 2MASX J20132145+6303444 2019-04-27 10:59 304.6876 +54.4322 2MASX J20184502+5425559 2019-04-27 11:02 353.4731 +80.9441 2MFGC 17682 2019-04-27 11:05 304.5325 +50.8713 2MASX J20180778+5052164 2019-04-27 11:12 302.3811 +48.1482 2MASX J20093146+4808535 2019-04-27 11:16 315.4480 +57.7256 2MASX J21014752+5743323 2019-04-27 11:19 306.0262 +68.2791 2MASX J20240632+6816442 2019-04-27 11:23 304.6915 +54.4077 UGC 11538 2019-04-27 11:26 302.9347 +62.4006 2MASX J20114430+6224020 2019-04-27 11:29 316.2281 +65.7095 2MASX J21045475+6542340 2019-04-27 11:33 305.4544 +44.0110 2MASX J20214907+4400399 2019-04-27 11:36 015.3454 +82.0982 2MASX J01012279+8205535 2019-04-27 11:40 324.9967 +78.4497 2MASX J21395910+7826585 2019-04-27 11:46 292.9330 +02.7058 2MASX J19314391+0242209 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24299 SUBJECT: LIGO/Virgo S190426c: J-GEM optical/NIR follow-up observations DATE: 19/04/27 20:03:16 GMT FROM: Yuu Niino at University of Tokyo Niino, Y., Morokuma, T., Ohsawa, R., Sako, S., Shikauchi, M. (U. of Tokyo), Yanagisawa, K. (NAOJ), Takagi K., Nakaoka, T., Sasada, M.(Hiroshima U.), Saito, T. (Nishi-Harima Astronomical observatory), Itoh, R. (Bisei Astronomical Observatory), Ohta, K. (Kyoto U.), Utsumi, Y. (Stanford U./SLAC), Sekiguchi, Y. (Toho U.), Tominaga, N. (Konan U.), on behalf of J-GEM collaboration We report our optical and near-infrared imaging observations for the gravitational wave event S190426c that has a non-zero probability to be a NS-BH merger. We performed 180 deg2 wide-field imaging survey, using the Tomo-e Gozen camera on the 105-cm Kiso Schmidt telescope, a very wide-field (20 deg2 field-of-view) optical CMOS imager (Sako et al. 2018, SPIE, 10702, 107020J). The observations started about 19 hours after the GW detection. A typical limiting magnitude is about 20 mag (no filter). Data reduction is in progress. We also performed galaxy-targeted observations for 33 galaxies (see the table below) selected from the GLADE catalog (Dalya et al. 2016) in the probability skymap of S190426c using the following telescopes/instruments. - 91 cm Okayama Astrophysical Observatory NIR Wide‐Field Camera (OAOWFC, J-band, Yanagisawa, K., et al. 2014, Proc. SPIE, 9147, 91476D, Yanagisawa, K., et al. 2016, Proc. SPIE, 9908, 99085D) - 150 cm Kanata telescope at Higashi-Hiroshima Observatory and HONIR, a 2 color imager in Rc and H bands (Akitaya et al. 2014, 9147, 91474O) - 200 cm Nayuta telescope at Nishi-Harima Astronomical Observatory and Nishiharima Infrared Camera (NIC) We found no apparent transient objects in these galaxies to the 5 sigma limiting magnitudes listed below. galid ra dec J H R NoFilt K obsid GL204400+531432 310.9979 53.2423 17.08 -- -- -- -- OAOWFC GL221519+843451 333.8273 84.581 -- -- -- 99.99 -- Kiso Schmidt GL232822+852913 352.0922 85.4869 -- 99.99 99.99 -- -- Kanata-HONIR GL233253+853017 353.222 85.5048 -- 15.35 17.65 -- -- Kanata-HONIR GL002228+854955 5.617 85.8321 17.33 17.24 -- -- 99.99 Nayuta GL011607+845904 19.0275 84.9843 -- -- -- -- 99.99 Nayuta GL235357+842524 358.4862 84.4233 -- -- -- 99.99 -- Kiso Schmidt GL233600+852510 353.9992 85.4196 -- -- 17.65 -- -- Kanata-HONIR GL235923+834710 359.8466 83.7861 -- 99.99 -- -- -- Kanata-HONIR GL223741+844405 339.4209 84.7347 -- -- -- 99.99 -- Kiso Schmidt GL215853+832141 329.7229 83.3614 -- -- -- 99.99 -- Kiso Schmidt GL214359+841507 325.9938 84.2519 -- -- -- 18.29 -- Kiso Schmidt GL222416+864727 336.0676 86.7909 -- -- -- 99.99 -- Kiso Schmidt GL205538+853151 313.9084 85.5307 -- -- -- 99.99 -- Kiso Schmidt GL233600+852604 353.9975 85.4346 -- 15.35 17.65 -- -- Kanata-HONIR GL201328+463031 303.3651 46.5087 17.57 -- -- -- -- OAOWFC GL221751+832357 334.4629 83.3993 -- -- -- 99.99 -- Kiso Schmidt GL205927+845437 314.8623 84.9103 -- -- -- 99.99 -- Kiso Schmidt GL224440+824209 341.1686 82.7026 -- -- -- 18.95 -- Kiso Schmidt GL225030+824531 342.6235 82.7586 -- -- -- 19.00 -- Kiso Schmidt GL201355+462212 303.4775 46.3701 17.57 -- -- -- -- OAOWFC GL235428+842518 358.6179 84.4217 -- -- -- 99.99 -- Kiso Schmidt GL223827+872835 339.6125 87.4764 -- -- -- 17.11 -- Kiso Schmidt GL180154+865139 270.4751 86.8608 -- -- -- 17.75 -- Kiso Schmidt GL233512+852612 353.7982 85.4366 -- 15.35 17.65 -- -- Kanata-HONIR GL215728+854334 329.3673 85.7262 -- -- -- 15.99 -- Kiso Schmidt GL194045+874800 295.188 87.7998 -- -- -- 17.69 -- Kiso Schmidt GL150924+865350 227.3519 86.8972 -- -- -- 99.99 -- Kiso Schmidt GL211419+871821 318.5808 87.3058 -- -- -- 17.59 -- Kiso Schmidt GL204129+862633 310.3714 86.4425 -- -- -- 99.99 -- Kiso Schmidt GL233452+852734 353.7174 85.4593 -- 15.35 17.65 -- -- Kanata-HONIR GL173106+875633 262.7764 87.9426 -- -- -- 18.29 -- Kiso Schmidt GL212800+853445 321.9959 85.5793 -- -- -- 18.29 -- Kiso Schmidt Note that a limiting mag = 99.99 is due to failure in our real-time data analysis. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24300 SUBJECT: LIGO/Virgo S190426c: RATIR Optical and NIR Observations of Galaxies DATE: 19/04/27 20:04:02 GMT FROM: Alan M Watson at UNAM Eleonora Troja (GSFC/UMD), Rosa L. Becerra (UNAM), Nat Butler (ASU), Alan M. Watson (UNAM), Simone Dichiara (UMD), Diego González (UNAM), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Margarita Pereyra (UNAM), and Tanner Wolfram (ASU) report: We observed 22 galaxies selected from the NED/CLU list for LIGO/Virgo S190426c (Chatterjee et al, GCN Circ. 24237) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir on the night of 2019-04-27 UTC. For each galaxy, we typically obtained 720 seconds of exposure in g and i filters and 540 seconds of exposure in Y and H filters. Typical 10-sigma limiting magnitudes are i = 21.2. Our observations are listed below. Visual inspection reveals no obvious counterpart candidates. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. Start (UTC) RA and Dec (J2000) Galaxy 2019-04-27 03:30 166.8817 +00.7831 IC 0671 2019-04-27 04:10 167.0731 -05.1323 MCG -01-29-002 2019-04-27 04:27 169.4779 -01.9464 IC 0680 2019-04-27 04:43 166.6895 -04.0722 2MASX J11064547-0404202 2019-04-27 05:10 166.3304 -03.9763 LCRS B110246.5-034222 2019-04-27 05:26 168.2716 +00.0030 2MASX J11130517+0000108 2019-04-27 05:43 170.8150 -05.5724 LCRS B112043.2-051740 2019-04-27 06:01 170.1643 -05.6714 MCG -01-29-010 NED01 2019-04-27 06:27 170.7156 -02.9109 CGCG 011-082 2019-04-27 07:19 168.0636 -05.7535 MCG -01-29-005 2019-04-27 07:50 169.4203 -04.4609 2MFGC 08820 2019-04-27 08:09 163.6089 +07.1427 CGCG 038-046 2019-04-27 08:27 300.5817 +43.1268 2MASX J20021959+4307366 2019-04-27 08:45 308.2331 +54.5088 UGC 11592 2019-04-27 09:12 311.7825 +57.5936 4C +57.35 2019-04-27 09:31 305.9863 +25.7011 2MASX J20235668+2542038 2019-04-27 09:52 302.6869 +17.7386 2MASX J20104485+1744189 2019-04-27 10:24 305.5413 +24.9932 2MASX J20220989+2459351 2019-04-27 10:42 300.6474 +14.9513 2MASX J20023539+1457045 2019-04-27 11:00 301.1253 +19.4085 2MASX J20043008+1924304 2019-04-27 11:16 299.3077 +19.0874 2MASX J19571383+1905142 2019-04-27 11:41 289.0384 -00.7858 2MFGC 14839 -- Dr. Alan M. Watson Instituto de Astronomía Universidad Nacional Autónoma de México //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24310 SUBJECT: LIGO/Virgo S190426c: DDOTI/OAN Optical Observations DATE: 19/04/27 23:52:48 GMT FROM: Alan M Watson at UNAM Alan M. Watson (UNAM), Nat Butler (ASU), Eleonora Troja (GSFC/UMD), Rosa L. Becerra (UNAM), Simone Dichiara (UMD), Diego González (UNAM), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Margarita Pereyra (UNAM), and Tanner Wolfram (ASU) report: We observed 8 fields of LIGO/Virgo S190426c (Chatterjee et al, GCN Circ. 24237) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx) on the night of 2019-04-27 UTC. Some fields were visited more than once. Each visit consisted of 1080 seconds in the w filter. Our observations are listed below. Analysis is proceeding. Due to hardware problems (a failed CCD power supply and a jammed focuser), we only observed with only four of the six telescopes and obtained about 48 square degrees at each visit rather than the full 72 square degrees. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. Start (UTC) RA and Dec (J2000) 2019-04-27 06:03 21:40:22.6 +85:17:25 2019-04-27 06:33 21:40:22.6 +85:17:25 2019-04-27 07:00 21:40:22.6 +85:17:25 2019-04-27 07:26 20:50:51.8 +63:40:00 2019-04-27 07:53 20:50:51.8 +63:40:00 2019-04-27 08:20 20:25:31.7 +47:46:54 2019-04-27 08:47 20:16:56.0 +39:52:13 2019-04-27 09:13 20:36:33.3 +56:11:28 2019-04-27 09:40 19:59:21.3 +24:29:14 2019-04-27 10:07 20:05:19.9 +31:51:18 2019-04-27 10:34 21:40:22.6 +85:17:25 2019-04-27 11:01 23:55:06.2 +83:59:48 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24316 SUBJECT: LIGO/Virgo S190426c: GROWTH India follow-up DATE: 19/04/28 02:06:16 GMT FROM: Harsh Kumar at Indian Inst of Tech,Bombay G. Waratkar, H. Kumar, V. Bhalerao, V. Karambelkar (IITB), G. C. Anupama, J. Stanzin (IIA) report on behalf of the GROWTH collaboration: We followed up the localization region of the GW candidate event S190426c (LVC et al. GCN 24168) with the GROWTH-India telescope. We obtained 37 r-band overlapping images covering a total area of 12.3 square degrees, with 9.43% probability of containing the GW counterpart. Exposures were 600 seconds long and reached a typical depth of 20.6 magnitude. The field centers (given below) were chosen in coordination with ZTF and DECAM (GCN 24257) to cover the northernmost part of the sky not accessible to them. Data processing is underway. These fields contain 332 galaxies from the GLADE catalog and 6 galaxies from NED. We inspected the NED galaxies (listed below) and do not find any candidate counterparts near them. List of NED galaxies: Name, RA, Dec 2MASX J22163720+8655469, 334.156, 86.929 VII Zw 938, 314.169, 87.880 HDCE 1209, 342.180, 86.83 UGC 12387, 346.084, 86.749 UGC 12377, 345.857, 86.766 CGCG 360-004, 18.977, 85.165 List of observed fields: RA Dec 315.000 87.441 003.214 84.882 012.273 85.979 018.750 85.613 009.000 84.516 010.385 85.247 003.462 85.247 343.125 87.076 004.091 85.979 016.071 84.882 337.500 87.807 322.500 87.807 354.375 87.076 355.500 86.345 353.571 87.441 005.625 87.076 356.538 85.247 335.000 86.710 331.875 87.076 015.000 84.516 340.714 87.441 325.000 86.710 355.000 86.710 009.643 84.882 013.500 86.345 017.308 85.247 003.750 85.613 327.857 87.441 005.000 86.710 352.500 87.807 345.000 86.710 008.438 84.150 356.250 85.613 320.625 87.076 004.500 86.345 011.250 85.613 328.500 86.345 The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7 degree field of view, set up by the Indian Institute of Astrophysics and the Indian Institute of Technology Bombay with support from the Indo-US Science and Technology Forum (IUSSTF) and the Science and Engineering Research Board (SERB) of the Department of Science and Technology (DST), Government of India (https://sites.google.com/view/growthindia/). It is located at the Indian Astronomical Observatory (Hanle), operated by the Indian Institute of Astrophysics (IIA). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24317 SUBJECT: LIGO/Virgo S190426c: DG19ytre and DG19kplb 1.5m OSN imaging and 10.4m GTC spectroscopy DATE: 19/04/28 02:42:09 GMT FROM: Alberto J. Castro-Tirado at IAA-CSIC A. F. Valeev and V. V. Sokolov (SAO-RAS), A. J. Castro-Tirado, Y.-D. Hu, X.-Y. Li, A. Ayala, E. Fernandez-Garcia and F. J. Aceituno (IAA-CSIC), I. Carrasco, A. Castellon and C. Perez del Pulgar (UMA), M. D. Caballero-Garcia (ASU-CAS), S. B. Pandey (ARIES) and N. Castro-Rodriguez (GRANTECAN, IAC, ULL), on behalf of a larger collaboration, report: Following the detection of the two new transients DG19ytre and DG19kplb (Andreoni et al., GCN 24268) within the error area of the GW event S190426c (LIGO Scientific Collaboration and the Virgo Collaboration, GCN 24237), we observed the two targets with the 1.5m telescope at the Observatorio de Sierra Nevada (Spain) in the BVRI-bands, starting on Apr 27, 20:53 UT. In addition, optical spectra for each target (1200s) covering the range 3700-7500 A were obtained with the 10.4m GTC telescope equipped with OSIRIS in La Palma (Spain) starting on Apr 27, 21:40 UT. DG19kplb is found to be in the outskirts of its host galaxy at a redshift z = 0.09123. The spectrum resembles that of a broad-line Type Ic SN at the same redshift past maximum. DG19ytre is north of a galaxy at redshift z = 0.1825 and displays Type Ia SN features consistent with z = 0.1386. Therefore none of these two newly reported transients seem to be related to the GW event S190426c. We acknowledge the excellent support from the GTC staff. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24322 SUBJECT: LIGO/Virgo S190426c: LOAO Observation DATE: 19/04/28 06:29:11 GMT FROM: Gregory SungHak Paek at SNU Gregory S.H. Paek (SNU), Myungshin Im (SNU), Hyun-Il Sung (KASI), Gu Lim (SNU), Joonho Kim (SNU), Sungyong Hwang (SNU), Bomi Park (SNU), Sophia Kim (SNU), Changsu Choi (SNU), Chung-Uk Lee (KASI), Seung-Lee Kim (KASI), Hyung Mok Lee (KASI), on behalf of a larger collaboration We observed 23 host galaxy candidates with the 1.0-m telescope at the Lemonsan Optical Astronomical Observatory(LOAO) in the 90% updated localization area of S190426c, detected by LIGO/Virgo (GCN #24237). The observation started at 2019-04-27 09:14:26, and the images were taken twice in R-band with 120 sec exposure time. No obvious transient has been identified to a preliminary 3-sigma depth of R=20.8 AB mag. The list of the inspected targets is given below. NAME RA DEC 2MASS+20300804+5415120 307.533508 54.253361 2MASS+20232657+5347113 305.860718 53.786499 2MASS+20175967+5440389 304.498657 54.677479 2MASS+20292607+5411091 307.358643 54.185883 2MASS+20205571+5530336 305.232147 55.509338 2MASS+20355212+5549587 308.967194 55.832996 2MASS+20305041+5537391 307.710052 55.627537 2MASS+20183442+5619548 304.643433 56.331894 2MASS+20360197+5350457 309.008209 53.846035 2MASS+20363163+5824495 309.131805 58.41375 2MASS+20403391+5348447 310.141296 53.812439 2MASS+20262902+5827565 306.620941 58.465717 2MASS+20290191+5817016 307.257996 58.283779 2MASS+20243518+5606523 306.146606 56.114536 2MASS+20235181+6448514 305.965881 64.814285 2MASS+20431631+6211283 310.817993 62.1912 2MASS+21072317+6322504 316.846558 63.38068 2MASS+20323093+6451261 308.128906 64.857254 2MASS+20391049+6303489 309.793732 63.063591 2MASS+20563318+6814486 314.138275 68.246841 2MASS+20453544+6259029 311.397705 62.984146 2MASS+21011016+6334464 315.292358 63.579582 2MASS+20550853+6249236 313.785583 62.823235 The observation of host galaxy candidates and the analysis of the data are ongoing. We thank the LOAO opertator for performing the observation. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24323 SUBJECT: LIGO/Virgo S190426c: ASAS-SN observations DATE: 19/04/28 06:35:36 GMT FROM: Benjamin Shappee at U. of Hawaii B. J. Shappee (IfA-Hawaii), C. S. Kochanek (OSU), K. Z. Stanek (OSU), S. Holmbo (Aarhus), A. Franckowiak (DESY), T. W.-S. Holoien (Carnegie Observatories), J. L. Prieto (Diego Portales; MAS), Subo Dong (KIAA-PKU), T. A. Thompson (OSU), J. F. Beacom (OSU) Following the LIGO/VIRGO alert of gravitational wave source S190426c (GCN # 24237), optical follow-up was triggered with the All-Sky Automated Survey for SuperNovae (ASAS-SN, Shappee et al. 2014; Kochanek et al. 2017). ASAS-SN covered 77% of the updated probability region (GCN #24277, 24279) in the 24 hours after the LIGO/VIRGO alert through a combination of normal operations and triggered observations. We note that we covered 86% of the preliminary localization region. We obtained up to 13 epochs on the highest probability regions during that time. Candidates were scanned in near real time. No obvious candidates were discovered. Given the lunation, our depth was typically between g~18-18.5 mag. Our coverage is shown here: http://www.astronomy.ohio-state.edu/~assassin/LIGO/S190426c_coverage.png Our coverage compared to the preliminary localization region is shown here: http://www.astronomy.ohio-state.edu/~assassin/LIGO/S190426c_prelim_coverage.png We would like to thank Las Cumbres Observatory and its staff for their continued support of ASAS-SN. ASAS-SN is funded in part by the Gordon and Betty Moore Foundation through grant GBMF5490 to the Ohio State University, NSF grant AST-1515927, the Mt. Cuba Astronomical Foundation, the Center for Cosmology and AstroParticle Physics (CCAPP) at OSU, the Chinese Academy of Sciences South America Center for Astronomy (CASSACA), and the Villum Fonden (Denmark). For more information about the ASAS-SN project, see http://www.astronomy.ohio-state.edu/asassn/index.shtml. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24327 SUBJECT: LIGO/Virgo S190426c: OAJ-GRANDMA observation report DATE: 19/04/28 11:20:48 GMT FROM: Martin Blazek at HETH/IAA-CSIC M. Blazek (HETH/IAA-CSIC), D. Corre (LAL), E. Howell (OzGrav-UWA), N. Christensen (Artemis), M. Vardosanidze (Iliauni), D. A. Kann (HETH/IAA-CSIC), K. Bensch (HETH/IAA-CSIC), L. Izzo (HETH/IAA-CSIC), C. Thoene (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), S. Antier (APC), S. Basa (LAM), M. Boer (Artemis), M. Coughlin (Caltech), D. Coward (OzGrav-UWA), J.G. Ducoin (LAL), B. Gendre (OzGrav-UWA), P. Hello (LAL), A. Klotz (IRAP), C. Lachaud (APC), N. Leroy (LAL), D. Turpin (NAOC), X. Wang (THU), and X. Zhang (THU) report on behalf of the HETH group and GRANDMA collaboration. We performed observations of LIGO/Virgo event S190426c (GCN #24237) with the OAJ-T80 telescope operating in the visible located at Javalambre astronomical observatory (Teruel, Spain). The observation started on 04/26/19 21:40:23 UTC which corresponds approximately to 6.3 hours after the GW trigger time. We performed the following observations in r band: +------------+------------+---------+---------+---------+ | Tstart | Tend | RA | DEC | Proba | | [UTC] | [UTC] | [deg] | [deg] | [%] | |------------+------------+---------+---------+---------| | 2019-04-26 | 2019-04-26 | 0.000 | 84.000 | 1.0 | | 21:40:23 | 21:43:24 | | | | | 2019-04-26 | 2019-04-26 | 340.000 | 84.000 | 0.7 | | 21:43:52 | 21:46:52 | | | | | 2019-04-26 | 2019-04-26 | 330.000 | 86.000 | 0.9 | | 21:50:01 | 21:53:01 | | | | | 2019-04-26 | 2019-04-26 | 0.000 | 82.000 | 0.4 | | 21:53:32 | 21:56:32 | | | | | 2019-04-26 | 2019-04-26 | 0.000 | 86.000 | 0.8 | | 21:56:59 | 22:00:00 | | | | | 2019-04-27 | 2019-04-27 | 309.600 | 56.000 | 0.5 | | 01:20:38 | 01:23:38 | | | | | 2019-04-27 | 2019-04-27 | 305.280 | 46.000 | 0.5 | | 01:28:57 | 01:31:58 | | | | | 2019-04-27 | 2019-04-27 | 301.935 | 30.000 | 0.4 | | 01:34:18 | 01:37:19 | | | | | 2019-04-27 | 2019-04-27 | 300.760 | 28.000 | 0.4 | | 01:37:46 | 01:40:46 | | | | | 2019-04-27 | 2019-04-27 | 306.000 | 48.000 | 0.4 | | 01:41:17 | 01:44:18 | | | | | 2019-04-27 | 2019-04-27 | 313.846 | 64.000 | 0.5 | | 01:47:29 | 01:50:29 | | | | | 2019-04-27 | 2019-04-27 | 309.231 | 64.000 | 0.4 | | 01:50:56 | 01:53:57 | | | | | 2019-04-27 | 2019-04-27 | 299.627 | 26.000 | 0.4 | | 01:54:34 | 01:57:35 | | | | | 2019-04-27 | 2019-04-27 | 300.789 | 32.000 | 0.4 | | 01:58:03 | 02:01:04 | | | | | 2019-04-27 | 2019-04-27 | 304.186 | 44.000 | 0.4 | | 02:01:33 | 02:04:33 | | | | | 2019-04-27 | 2019-04-27 | 302.013 | 34.000 | 0.4 | | 02:07:46 | 02:10:47 | | | | | 2019-04-27 | 2019-04-27 | 306.783 | 50.000 | 0.4 | | 02:11:16 | 02:14:16 | | | | | 2019-04-27 | 2019-04-27 | 310.737 | 58.000 | 0.4 | | 02:14:48 | 02:17:48 | | | | | 2019-04-27 | 2019-04-27 | 302.897 | 36.000 | 0.4 | | 02:18:22 | 02:21:22 | | | | | 2019-04-27 | 2019-04-27 | 303.830 | 38.000 | 0.4 | | 02:25:13 | 02:28:14 | | | | | 2019-04-27 | 2019-04-27 | 298.537 | 24.000 | 0.4 | | 02:28:43 | 02:31:43 | | | | | 2019-04-27 | 2019-04-27 | 308.571 | 54.000 | 0.4 | | 02:32:20 | 02:35:20 | | | | +------------+------------+---------+---------+---------+ The probability refers to the 2D spatial probability of the GW (initial) skymap enclosed in a given tile. Each tile is 1.4x1.4 degrees. These observations cover about 11% of the cumulative probability of the skymap. The typical limiting magnitude is 19.6 for a 180 s exposure. The coverage map is available at: https://grandma-owncloud.lal.in2p3.fr/index.php/s/jWlewyAy823F2sZ No transients related to the GW event have been found when comparing sky regions around GLADE galaxies with PS1 template observations. GRANDMA (Global Rapid Advanced Network Devoted to the Multi-messenger Addicts) is a network of robotic telescopes connected all over the world with both photometry and spectrometry capabilities for Time-domain Astronomy (https://grandma.lal.in2p3.fr/). HETH (High Energy Transients and Their Hosts) is funded by Spanish National Research Grant of Excellence, Ramon y Cajal fellowships and research funding, Juan de la Cierva Incorporation fellowships and research funding (http://heth.iaa.es/). Details on the OAJ-T80 telescope are available at http://oajweb.cefca.es This circular is citable. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24329 SUBJECT: LIGO/Virgo S190426c: Continued infrared wide-field search with Palomar Gattini-IR DATE: 19/04/28 15:04:06 GMT FROM: Matthew Hankins at Caltech M. Hankins (Caltech), K. De (Caltech), M. Coughlin (Caltech), M. M. Kasliwal (Caltech), S. M. Adams (Caltech), I. Andreoni (Caltech), S. Anand (Caltech), L. Singer (NASA GSFC), T. Ahumada (UMD), A. Moore (ANU), J. Soon (ANU), M. Ashley (UNSW), T. Travouillon (ANU), R. Lau (ISAS JAXA) report on behalf of the Palomar Gattini-IR team and the larger GROWTH (Global Relay of Observatories Watching Transients Happen) collaboration We report continuing wide-field near-infrared follow-up observations (GCN #24284) of the localization region of the gravitational wave event S190426c (GCN #24237) by the Palomar Gattini-IR survey (Moore and Kasliwal 2019). Gattini-IR is a newly commissioned near-IR camera with a field of view of 25 square degrees mounted on a robotic 30 cm telescope at Palomar observatory. We started customized Target of Opportunity observations at UT 2019-04-28 03:28. The tiling was optimally determined and triggered using the GROWTH Target of Opportunity marshal (Coughlin et al. 2019a, Kasliwal et al. 2019b). We imaged a total of 1900 square degrees, covering 94% of the probability region of the event for 1 to 5 epochs until UT 2019-04-28 12:33. Each field visit consisted of a sequence of 8 dithers of 8 second exposures each on the field, which were processed and stacked with the Palomar Gattini-IR data reduction pipeline (De et al., in prep.). The typical limiting magnitude of each stacked epoch (64 second exposure time) was between 14.5 and 15.5 AB mag in J-band, and shallower than usual due to poor weather conditions. No viable counterparts without previous history of variability were identified. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24331 SUBJECT: LIGO/Virgo S190426c: Additional Candidates from the Zwicky Transient Facility DATE: 19/04/28 16:30:41 GMT FROM: Daniel Perley at Liverpool JMU Daniel A. Perley (LJMU), Ariel Goobar (OKC), Mansi M. Kasliwal (Caltech), Michael W. Coughlin (Caltech), Adam A. Miller (Northwestern), Tomas Ahumada (UMD), Jacob Jencson (Caltech), Harsh Kumar (IITB), David Kaplan (UWM), Shreya Anand (Caltech), Leo P. Singer (NASA GSFC), Igor Andreoni (Caltech), Varun Bhalerao (IITB), Danny Goldstein (Caltech), Dmitry Duev (Caltech), S. Bradley Cenko (NASA GSFC), Eric C. Bellm (UW), Kishalay De (Caltech), Rahul Biswas (OKC), Kishalay De (Caltech), and Joshua Bloom (UCB) report on behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: We continued observations of the gravitational wave trigger S190426c (LVC et al. GCN 24237) with ZTF on UT 2019-04-28. We covered 1150 sq deg in g-band and r-band with over 54% of the enclosed probability targeted based on the latest sky map (LALInference1.fits.gz, GCN 24277). Each exposure on the second night was 300s, with a typical depth of 22 mag. In total, over both nights, we have covered 4420 sq deg, enclosing 56% of the the total probability. See details in Coughlin et al. (GCN 24283) for additional details on data processing. Additional candidates with no detections prior to merger, inside the 90% localization area of the LALInference sky map, and not consistent with the locations of known AGN or other variable objects, are: ------------------------------------------------------------------------------------------------ ZTF Name | RA (deg) | DEC (deg) | Filt.| Mag. | Magerr | Notes ------------------------------------------------------------------------------------------------ ZTF19aasmftm | 325.9004479 | 77.8315634 | g | 21.16 | 0.12 | [rising] ZTF19aaslvwn | 299.059846 | 46.463559 | g | 20.83 | 0.12 | [lowb] ZTF19aasmdir | 300.2360007 | 9.504002 | g | 20.35 | 0.09 | [lowb] [nuc] [agn?] ZTF19aaslzjf | 320.6262982 | 65.8134516 | r | 20.54 | 0.09 | [lowb] ZTF19aassfws | 298.6678611 | 61.2400121 | r | 21.41 | 0.20 | photz~0.07 +/- 0.03 [nuc] ZTF19aasmddt | 299.25055 | 9.7016748 | g | 20.00 | 0.08 | photz~0.08 +/- 0.04 [lowb] ZTF19aaslszp | 301.3434628 | 53.3990477 | g | 20.84 | 0.11 | photz~0.062 [lowb] [nuc?] ZTF19aasmekb | 300.6013987 | 14.2873159 | g | 18.29 | 0.03 | [lowb] [hostless] [fading] ZTF19aaslolf | 288.7838539 | 79.4357187 | g | 21.33 | 0.19 | photz~0.42+/-0.20 [nuc] [agn?] ZTF19aaslphi | 297.3809977 | 61.9605925 | g | 21.24 | 0.17 | photz~0.16+/-0.02 ZTF19aaslpds | 306.2625186 | 61.521461 | r | 20.99 | 0.13 | [lowb] ZTF19aaslozu | 306.3144981 | 65.1093759 | r | 20.87 | 0.16 | ZTF19aasshpf | 315.4768651 | 70.2055771 | r | 21.42 | 0.18 | ZTF19aasmzee | 296.8366485 | 5.1534971 | r | 20.33 | 0.09 | [lowb] ZTF19aasmzqf | 353.5204911 | 78.9577781 | g | 20.53 | 0.09 | ---------------------------------------------------------------------------------------------- Notes: [rising] : Rising light curve [lowb] : Galactic latitude less than 15 degrees [agn?] : WISE colors consistent within an AGN within 1" of the transient. [hostless] : No discernable host galaxy or other counterpart. [nuc] : Close to the host nucleus. [fading] : Clear fading is observed over the past two nights, with no prior rise. This may indicate a CV / dwarf nova. Three candidates (ZTF19aassfws, ZTF19aasmddt, ZTF19aaslszp) are interesting given that their photometric redshifts are consistent with the LVC error volume. ZTF19aaslzjf is also in a galaxy that is likely nearby, although no redshift estimate is available. ZTF19aasmftm is interesting given a (probable) rising light curve that suggests a young object, although its galaxy counterpart is very faint (r=21.2 in PS1). Deep upper limits preceding the detections are not available for any of these sources, and they could be unrelated SNe. Additional follow-up and analysis is ongoing. ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan; IIT-B, India; IIA, India; LJMU, UK; TTU USA and USyd, Australia. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert filtering and follow-up co-ordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019). DisclaimerNone //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24336 SUBJECT: LIGO/Virgo S190426c: Continued LOAO Observation DATE: 19/04/29 03:13:42 GMT FROM: Gregory SungHak Paek at SNU Gregory S.H. Paek (SNU), Myungshin Im (SNU), Hyun-Il Sung (KASI), Gu Lim (SNU), Joonho Kim (SNU), Sungyong Hwang (SNU), Bomi Park (SNU), Sophia Kim (SNU), Changsu Choi (SNU), Chung-Uk Lee (KASI), Seung-Lee Kim (KASI), Hyung Mok Lee (KASI), on behalf of a larger collaboration We observed 17 host galaxy candidates with the 1.0-m telescope at the Lemonsan Optical Astronomical Observatory(LOAO) in the 90% updated localization area of S190426c, detected by LIGO/Virgo (GCN #24237). The observation started at 2019-04-28 09:59:34.500, and the images were taken twice in R-band with 120 sec exposure time. No obvious transient has been identified to a preliminary 3-sigma depth of R=19.6 AB mag. The list of the inspected targets is given below. NAME RA DEC 2MASS+00320124+8337292 00:32:01.200 +83:37:29.30 2MASS+00431317+8418363 00:43:13.200 +84:18:36.30 2MASS+00432208+8527102 00:43:22.100 +85:27:10.30 2MASS+00450100+8538272 00:45:01.000 +85:38:27.20 2MASS+00533469+8539080 00:53:34.700 +85:39:08.10 2MASS+00592185+8521346 00:59:21.900 +85:21:34.70 2MASS+01042304+8335416 01:04:23.000 +83:35:41.70 2MASS+01051541+8511586 01:05:15.400 +85:11:58.60 2MASS+01065962+8521066 01:06:59.600 +85:21:06.70 2MASS+01073984+8711285 01:07:39.800 +87:11:28.60 2MASS+01125057+8546555 01:12:50.600 +85:46:55.60 2MASS+01160660+8459035 01:16:06.600 +84:59:03.50 2MASS+01190649+8504131 01:19:06.500 +85:04:13.20 2MASS+01264881+8506094 01:26:48.800 +85:06:09.50 2MASS+01333891+8532521 01:33:38.900 +85:32:52.20 PGC3005 00:52:03.700 +85:23:32.60 PGC3085929 00:41:52.300 +84:22:56.10 We thank the LOAO opertator for performing the observation. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24340 SUBJECT: LIGO/Virgo S190426c: GRAWITA transients from Asiago Schmidt wide field observations DATE: 19/04/29 10:31:43 GMT FROM: Andrea Melandri at INAF-OAB L. Izzo (IAA), R. Carini (INAF-OAR), S. Yang (INAF-OAPd), L. Tomasella (INAF-OAPd), E. Cappellaro (INAF-OAPd), G. Greco (Univ. Urbino), R. Martone (U. Ferrara), S. Benetti (INAF-OAPd), M.T. Botticella (INAF-OAC), M. Branchesi (GSSI), S. Campana (INAF-OAB), S. Covino (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASI-SSDC), M. Della Valle (INAF-OAC), A. Melandri (INAF-OAB), S. Piranomonte (INAF-OAR), A. Rossi (INAF-OAS), E. Brocato (INAF-OAAb, INAF-OAR), on behalf of GRAWITA report: We carried out observations of LIGO/Virgo S190426c (LVC, GCN Circ. 24237) with the Schmidt Telescope located at the INAF Asiago Observatory (Italy). The observations were taken in the r-sloan band on 2019-04-26 starting on 22:16:27 UT. Each pointing covers an area of 1x1 deg and each exposure was of 90 s. The covered area captured a contained probability of ~1.6% of the GW skymap (LALInference1, submitted by LIGO/Virgo EM Follow-Up on Apr 27, 2019 11:50:29 UTC). The pointings are centered on the following UT times and coordinates RA(J2000), Dec(J2000): 2019-04-26T22:27:23 22:19:19.87 +82:59:58 2019-04-26T22:32:38 22:19:20.51 +84:59:59 2019-04-26T22:37:08 21:59:57.43 +83:00:00 2019-04-26T22:40:52 22:00:00.31 +84:00:00 2019-04-26T22:44:49 21:59:59.51 +84:59:59 A preliminary analysis of the dataset reveals the presence of the following transient sources (ID, RA(J2000, Dec(J2000), r(AB) mag, probability by LALInference1 skymap): GRAWITA_J215716.26+832239.4 21:57:16.26 +83:22:39.4 15.1 within 30% c.r. GRAWITA_J220104.54+834836.9 22:01:04.54 +83:48:36.9 16.9 within 30% c.r. GRAWITA_J220050.38+844436.5 22:00:50.38 +84:44:36.5 16.7 within 20% c.r. There are no known source at the position of these sources and no minor planets. Inspection of archival Pan-STARRS images reveals no objects at the position of GRAWITA_J215716.26+832239.4 and GRAWITA_J220104.54+834836.9, while a faint source can be recognised at the position of GRAWITA_J220050.38+844436.5. Subsequently, we carried out follow-up observations, starting at 22:58:43 UT on 2019-04-28, with the 0.5m telescope of the Osservatorio Astronomico S. Di Giacomo located in Agerola, Italy (https://goo.gl/Dqvqhf) of GRAWITA_J220104.54+834836.9 and GRAWITA_J220050.38+844436.5. Both sources are no longer detected down to a 3sigma limiting magnitude of R(AB)>19.4. Further analysis is in progress. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24341 SUBJECT: LIGO/Virgo S190426c: MASTER analysys of GRAWITA transients DATE: 19/04/29 11:47:01 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, N.Tyurina, E. Gorbovskoy, V.Kornilov, D.Vlasenko, V.Vladimirov, D.Zimnukhov, A.Kuznetsov, P.Balanutsa, I.Gorbunov, A. Chasovnikov, V.Grinshpun, F.Balakin, T.Pogrosheva (Lomonosov Moscow State University, SAI, Physics Department), R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres (The Instituto de Astrofisica de Canarias), R. Podesta, C. Lopez, C.Francile, F. Podesta (Observatorio Astronomico Felix Aguilar OAFA, San Juan National University), H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE,SJNU) D. Buckley (South African Astronomical Observatory), O. Gress, N.M. Budnev, O.Ershova (Applied Physics Institute, Irkutsk Stat University), V. Yurkov, A. Gabovich, Yu. Sergienko, D. Kobcev (Blagoveschensk EducationState University), A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), MASTER Global Robotic Net (http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) started inspect of GW190426 / LIGO/Virgo S190426c errorbox (Chatterjee et al. GCN 24237 https://gcn.gsfc.nasa.gov/other/S190426c.gcn3 ) at 2019-04-26 16:15:47 UT (Lipunov et al. GCN 24236) and continuied several nights. There is no OTs at GRAWITA positions ( Izzo et al. GCN 24340 ) several hours befor 1) 21 57 16.26 +83 22 39.4 Date_UT unfiltmlim MASTER_observatory 2019-04-26 20:38:02 19.6 MASTER-Kislovodsk 2019-04-26 18:38:53 19.6 MASTER-Tavrida 2019-04-26 16:41:15 19.2 MASTER-Tunka There is variable star in 5", presented in GSC2.3.2 (red fmag=19.9 in 1996), PanSTARR source with rmag=20.73(2010Dec30). It's not presented in USNO-B1, it means 22mPOSS limit in history. 2) 22:01:04.54 +83:48:36.9 Date_UT unfiltmlim MASTER_observatory 2019-04-26 20:38:02 19.6 MASTER-Kislovodsk 2019-04-26 18:38:53 19.6 MASTER-Tavrida 2019-04-26 16:25:18 19.6 MASTER-Tunka 2019-04-27 11:59:22 16.5 MASTER-Amur there is also a star in 6.9" in PanSTARR catalogue with imag=21.14 (no g,r) 3) 22 00 50.38 +84 44 36.5 Date_UT unfiltmlim MASTER_observatory 2019-04-26 20:56:51 20.0 MASTER-Tavrida 2019-04-26 20:38:02 19.7 MASTER-Kislovodsk 2019-04-26 16:25:18 19.5 MASTER-Tunka There is a star in 4.3" in USNO-B1 (B1=20.77,R1=19.08) with proper motion . The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24342 SUBJECT: LIGO/Virgo S190426c: Fermi-LAT search for a high-energy gamma-ray counterpart DATE: 19/04/29 12:32:45 GMT FROM: Magnus Axelsson at Stockholm U. M. Axelsson (KTH & Stockholm Univ.), E. Bissaldi (INFN and Politecnico Bari), D. Kocevski (NASA/MSFC), F. Longo (University and INFN, Trieste), and N. Omodei (Stanford Univ.) report on behalf of the Fermi-LAT Collaboration: We have searched data collected by the Fermi Large Area Telescope (LAT) on April 26, 2019, for possible high-energy (E > 100 MeV) gamma-ray emission in spatial/temporal coincidence with the LIGO/Virgo trigger S190426c (GCN 24237). We define "instantaneous coverage" as the integral over the region of the LIGO probability map that is within the LAT field of view at a given a time, and "cumulative coverage" as the integral of the instantaneous coverage over time. Fermi-LAT had instantaneous coverage of ~85% of the LIGO probability at the time of the trigger (T0 = 2019-04-26 15:21:55.337 UTC), and reached ~95% cumulative coverage after ~4 ks. Due to the observing pattern of Fermi, the remaining area was not observed for more than 24 hours after the trigger time of the event. We performed a search for a transient counterpart within the observed region of the 90% contour of the LIGO map in a fixed time window from T0 to T0 + 10 ks. We also performed a search which adapted the time interval of the analysis to the exposure of each region of the sky, and no additional excesses were found. Energy flux upper bounds for the fixed time interval between 100 MeV and 100 GeV for this search vary between 1e-10 and 3.2e-7 [erg/cm^2/s]. The Fermi-LAT point of contact for this event is Magnus Axelsson (magaxe@kth.se). The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24344 SUBJECT: LIGO/Virgo S190426c: Gaia Photometric Alerts transient candidate DATE: 19/04/29 15:57:48 GMT FROM: Zuzanna Kostrzewa-Rutkowska at SRON Z. Kostrzewa-Rutkowska (SRON/RU), S. Hodgkin, A. Delgado, D.L. Harrison, M. van Leeuwen, G. Rixon, A. Yoldas (IoA Cambridge), D. Eappachen, P.G. Jonker (SRON/RU) on behalf of Gaia Alerts team report the discovery of a transient candidate within the probability skymap of S190426c (LIGO/VIRGO Collaboration GCN Circ. 24237): --------------------------------------------------------------------------- Name TNSid Date [TCB] RaDeg DecDeg AlertMag URL --------------------------------------------------------------------------- Gaia19boq AT2019egk 2019-04-27T19:35:33 319.09753 58.89088 18.67 http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19boq/ --------------------------------------------------------------------------- Acknowledgements: This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. ZKR, DE, and PGJ acknowledge support from the European Research Council under ERC Consolidator Grant agreement no 647208. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24346 SUBJECT: LIGO/Virgo S190426c: YAHPT Optical Observation DATE: 19/04/29 17:45:58 GMT FROM: Tianrui Sun at Purple Mountain Obs,CAS Tianrui Sun,Jian Chen,Lei Hu,Fan Li, Ye Yuan, Yanning Fu, Yue Chen.,Xuefeng Wu,Kelai Meng(PMO), Wen-xiong Li, Xinghan Zhang,Xiao-feng Wang(THU), Lifan Wang(PMO and TAMU) We report the observations of the updated localization with GLADE(Dalya et al., 2018, MNRAS, 479, 2374) catalogue of the gravitational event S190426c (The LIGO Scientific Collaboration and the Virgo Collaboration, GCN 24277,24237) with the Yaoan High Precision Telescope at Yaoan Observation Station(in Yunnan Province, China(101.1811 E,25.528N)), Purple Mountain Observatory. We obtained images of 48 galaxies in Rc band with exposure time 120s and calibrated to the PPMX catalogue (Roeser, 2008) .No obvious transient has been identified. The list of the observed/inspected targets and its 5-sigma magnitude limit is given below. Object |RA DEC |ObserveTime |MagLimit(err) 2MASS_J00055155+8537092 | 00:05:51.000 +85:37:09.00 | 2019-04-27T17:31:10 | 18.40(0.070) 2MASS_J00060903+8426372 | 00:06:09.000 +84:26:37.00 | 2019-04-27T18:20:39 | 18.09(0.098) 2MASS_J00084951+8555097 | 00:08:49.000 +85:55:09.00 | 2019-04-27T18:25:25 | 18.05(0.075) 2MASS_J00092210+8506409 | 00:09:22.000 +85:06:40.00 | 2019-04-27T18:42:10 | 17.94(0.079) 2MASS_J00142097+8440183 | 00:14:20.000 +84:40:18.00 | 2019-04-27T16:57:51 | 18.26(0.060) 2MASS_J00143375+8524234 | 00:14:33.000 +85:24:23.00 | 2019-04-27T14:08:57 | 19.23(0.051) 2MASS_J00152318+8610254 | 00:15:23.000 +86:10:25.00 | 2019-04-27T15:49:52 | 18.71(0.080) 2MASS_J00171922+8412432 | 00:17:19.000 +84:12:43.00 | 2019-04-27T18:39:45 | 15.29(0.175) 2MASS_J00222807+8549554 | 00:22:28.000 +85:49:55.00 | 2019-04-27T17:20:49 | 18.35(0.092) 2MASS_J00224102+8601575 | 00:22:41.000 +86:01:57.00 | 2019-04-27T17:16:57 | 18.75(0.060) 2MASS_J00240580+8413520 | 00:24:05.000 +84:13:52.00 | 2019-04-27T17:35:09 | 18.10(0.096) 2MASS_J00264523+8444573 | 00:26:45.000 +84:44:57.00 | 2019-04-27T18:51:44 | 17.91(0.079) 2MASS_J00282377+8606093 | 00:28:23.000 +86:06:09.00 | 2019-04-27T18:58:44 | 18.16(0.070) 2MASS_J00310187+8420369 | 00:31:01.000 +84:20:36.00 | 2019-04-27T19:08:19 | 17.94(0.067) 2MASS_J00373257+8410452 | 00:37:32.000 +84:10:45.00 | 2019-04-27T19:20:07 | 17.76(0.096) 2MASS_J00415229+8422560 | 00:41:52.000 +84:22:56.00 | 2019-04-27T15:01:47 | 19.03(0.073) 2MASS_J00430464+8800328 | 00:43:04.000 +88:00:32.00 | 2019-04-27T16:41:03 | 18.64(0.114) 2MASS_J00431317+8418363 | 00:43:13.000 +84:18:36.00 | 2019-04-27T15:17:08 | 14.75(0.039) 2MASS_J00432208+8527102 | 00:43:22.000 +85:27:10.00 | 2019-04-27T17:46:45 | 18.43(0.079) 2MASS_J00434058+8446222 | 00:43:40.000 +84:46:22.00 | 2019-04-27T16:47:22 | 18.44(0.043) 2MASS_J00460455+8539449 | 00:46:04.000 +85:39:44.00 | 2019-04-27T19:01:09 | 17.74(0.100) 2MASS_J00520371+8523325 | 00:52:03.000 +85:23:32.00 | 2019-04-27T15:45:58 | 18.94(0.048) 2MASS_J00553194+8500374 | 00:55:31.000 +85:00:37.00 | 2019-04-27T18:32:40 | 18.16(0.073) 2MASS_J00592185+8521346 | 00:59:21.000 +85:21:34.00 | 2019-04-27T16:37:05 | 18.75(0.069) 2MASS_J00592917+8732280 | 00:59:29.000 +87:32:28.00 | 2019-04-27T14:59:21 | 19.35(0.082) 2MASS_J01135181+8724333 | 01:13:51.000 +87:24:33.00 | 2019-04-27T17:13:04 | 18.68(0.077) 2MASS_J01150199+8620395 | 01:15:01.000 +86:20:39.00 | 2019-04-27T17:42:01 | 18.03(0.096) 2MASS_J01160660+8459035 | 01:16:06.000 +84:59:03.00 | 2019-04-27T15:13:48 | 15.42(0.039) 2MASS_J01215684+8458118 | 01:21:56.000 +84:58:11.00 | 2019-04-27T18:01:34 | 17.86(0.142) 2MASS_J01230987+8524108 | 01:23:09.000 +85:24:10.00 | 2019-04-27T15:56:04 | 18.81(0.060) 2MASS_J01264881+8506094 | 01:26:48.000 +85:06:09.00 | 2019-04-27T17:01:44 | 18.32(0.074) 2MASS_J01333891+8532521 | 01:33:38.000 +85:32:52.00 | 2019-04-27T16:16:55 | 18.42(0.079) 2MASS_J19321273+8812473 | 19:32:12.000 +88:12:47.00 | 2019-04-27T18:15:51 | 18.58(0.084) 2MASS_J20412914+8626330 | 20:41:29.000 +86:26:33.00 | 2019-04-27T17:27:13 | 19.07(0.039) 2MASS_J20441724+8654219 | 20:44:17.000 +86:54:21.00 | 2019-04-27T16:23:13 | 18.77(0.076) 2MASS_J20522972+8611119 | 20:52:29.000 +86:11:11.00 | 2019-04-27T16:44:59 | 19.11(0.078) 2MASS_J21213146+8713544 | 21:21:31.000 +87:13:54.00 | 2019-04-27T18:22:59 | 18.31(0.054) 2MASS_J22120284+8552027 | 22:12:02.000 +85:52:02.00 | 2019-04-27T15:06:35 | 17.53(0.136) 2MASS_J22470787+8450298 | 22:47:07.000 +84:50:29.00 | 2019-04-27T19:22:26 | 17.98(0.061) 2MASS_J22544273+8544285 | 22:54:42.000 +85:44:28.00 | 2019-04-27T18:35:00 | 20.51(0.039) 2MASS_J22582128+8648054 | 22:58:21.000 +86:48:05.00 | 2019-04-27T18:05:31 | 18.38(0.076) 2MASS_J23091312+8512017 | 23:09:13.000 +85:12:01.00 | 2019-04-27T18:49:24 | 17.94(0.104) 2MASS_J23151704+8433526 | 23:15:17.000 +84:33:52.00 | 2019-04-27T19:05:59 | 18.13(0.096) 2MASS_J23193319+8758310 | 23:19:33.000 +87:58:31.00 | 2019-04-27T15:34:19 | 18.47(0.077) 2MASS_J23252375+8752450 | 23:25:23.000 +87:52:45.00 | 2019-04-27T16:53:54 | 18.55(0.064) 2MASS_J23345217+8527335 | 23:34:52.000 +85:27:33.00 | 2019-04-27T18:56:24 | 17.92(0.075) 2MASS_J23505702+8511090 | 23:50:57.000 +85:11:09.00 | 2019-04-27T18:44:35 | 17.95(0.085) 2MASS_J23574733+8500029 | 23:57:47.000 +85:00:02.00 | 2019-04-27T14:11:17 | 18.85(0.039) [GCN OPS NOTE(07may19): Per author's request, the typo in the SUBJECT-line was changed from "25c" to "26c".] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24349 SUBJECT: LIGO/Virgo S190426c: PS1 historical detections and ZTF photometry of Gaia19boq AT2019egk DATE: 19/04/30 04:46:24 GMT FROM: Igor Andreoni at Caltech Igor Andreoni (Caltech), Shreya Anand (Caltech), Mansi Kasliwal (Caltech) On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations We report photometry and historical detections of the transient candidate Gaia19boq AT2019egk (Kostrzewa-Rutkowska et al., GCN 24344). Previous detections are reported in the Pan-STARRS1 Data Release 2 database (Chambers et al., 2016) at coordinates consistent with Gaia19boq, suggesting outburst history. The following table summarizes the ZTF photometry of the source on the days near the gravitational wave event S190426c (LIGO and Virgo Collaboration, GCN 24237). ---------------------------------------------------- Date (UTC) | filter | mag | err ---------------------------------------------------- 2019-04-24 10:41:57.120 | r | >20.02 | - 2019-04-27 08:29:28.320 | g | 18.88 | 0.04 2019-04-27 09:54:51.840 | r | 18.51 | 0.04 2019-04-28 08:28:10.560 | g | 19.02 | 0.04 The Gaia19boq transient, dubbed also ZTF19aaslxmg, shows red color and rapid evolution within 2 days after the gravitational wave event S190426c (LIGO and Virgo Collaboration, GCN 24237). The red color could be due to high Galactic extinction E(B-V) = 0.9733 magnitudes (Schlafly & Finkbeiner, 2011). We conclude that Gaia19boq AT2019egk is a Galactic variable source unrelated with the gravitational wave event S190426c (LIGO and Virgo Collaboration, GCN 24237). ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan; IIT-B, India; IIA, India; LJMU, UK; TTU USA and USyd, Australia. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert filtering and follow-up co-ordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24351 SUBJECT: LIGO/Virgo S190426c: GROWTH India follow-up of GRAWITA transient DATE: 19/04/30 10:43:09 GMT FROM: Harsh Kumar at Indian Inst of Tech,Bombay H. Kumar, V. Karambelkar, V. Bhalerao, K Deshmukh, M. Khandagale (IITB), G. C. Anupama, T. Stanzin, U. Stanzin (IIA) report on behalf of the GROWTH collaboration: We observed the field of GRAWITA_J215716.26+832239.4 reported by L. Izzo et.al. (GCN 24340) at 2019-04-29T21:04:39.694 UT with the 0.7m GROWTH-India telescope. The image was taken in r filter with 600 sec exposure. We did not find any source at the specified position up to mag_lim ~ 19.8, calibrated with PS1 photometry. We also continued follow-up of the localisation region of the GW candidate event S190426c (LVC et al. GCN 24168, G. Waratkar et. al. GCN 24316) with the GROWTH-India telescope in the northernmost part of the sky. We obtained 43 r-band overlapping images covering a total area of 12.1 square degrees, with 8.9% probability of containing the GW counterpart on 20190428 and 16 r-band overlapping images covering a total area of 4.4 square degrees, with 4.1% probability of on 20190829. Exposures were 600 seconds long and reached a typical depth of 20.5 magnitude. Data processing is underway. On 20190428 (20190429), these fields contain 313(104) galaxies from the GLADE catalog and 10(4) galaxies from NED. No obvious transients were seen in the NED galaxies. The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7 degree field of view, set up by the Indian Institute of Astrophysics and the Indian Institute of Technology Bombay with support from the Indo-US Science and Technology Forum (IUSSTF) and the Science and Engineering Research Board (SERB) of the Department of Science and Technology (DST), Government of India (https://sites.google.com/view/growthindia/). It is located at the Indian Astronomical Observatory (Hanle), operated by the Indian Institute of Astrophysics (IIA). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24353 SUBJECT: LIGO/Virgo S190426c: Swift rapid follow-up observations of S190425z and S190426c and URL for observation log for all future events DATE: 19/04/30 13:44:57 GMT FROM: Aaron Tohuvavohu at PSU/Swift A. Tohuvavohu (PSU), P.A. Evans (U. Leicester), J.A. Kennea (PSU), S.B. Cenko (NASA/GSFC), S.D. Barthelmy (NASA/GSFC), A.P. Beardmore (U. Leicester), A.A. Breeveld (UCL-MSSL), D.N. Burrows (PSU), S. Campana (INAF-OAB), G. Cusumano (INAF-IASF PA), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V.D'Elia(ASDC), S.W.K. Emery (UCL-MSSL), P. Giommi (ASI), C. Gronwall (PSU), D. Hartmann (U. Clemson), N. J. Klingler (PSU), H.A. Krimm (CRESST/GSFC/USRA), N.P.M. Kuin (UCL-MSSL), A.Y. Lien (GSFC/UMBC), D. Malesani (DARK/NBI), F.E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), J.A. Nousek (PSU), S.R. Oates (U. Warwick), P.T. O'Brien (U. Leicester), J.P. Osborne (U. Leicester), C. Pagani (U. Leicester), K.L. Page (U.Leicester), D.M. Palmer (LANL), M. Perri (ASDC), J.L. Racusin (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU), M.H. Siegel (PSU), G. Tagliaferri (INAF-OAB), E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team: The Neil Gehrels Swift Observatory UVOT and XRT instruments began pointed galaxy-targeted followup of the LIGO/Virgo detected S190425z (LVC GCN. 24168) at 2019-04-25 12:53 UT (T0+274 min), delayed due to a commanding gap. The observations continued until 2019-04-26 20:15 UT, when they were aborted to begin followup of S190426c (LVC GCN. 24237). The completed campaign comprised ~400 fields, covering several hundred of the most massive galaxies in the localization volume. The Swift UVOT and XRT began pointed galaxy-targeted followup of the LIGO/Virgo detected S190426c (LVC GCN. 24237) at 2019-04-26 17:45:00 UT (T0+142 min) and continued until T0+~48 hours. The completed campaign comprised ~800 fields, covering >30% of the galaxy-convolved localization region of the 'LALInference1' skymap. The GW rapid followup observations have a nominal 80 s duration, and are performed primarily with the u filter and with XRT in PC mode. The average limiting magnitude achieved is ~18.6 in u, and ~5 x 10^-12 erg s^-1 cm^-2 in soft X-rays (0.3-10 keV). Analysis of the data is ongoing, and candidate counterparts will be reported as found. A list of observed fields, times, and associated target IDs can be found at the following URL for these triggers and for all future GW followup: http://www.swift.ac.uk/LVC/ We remind the community that all Swift data are public, and encourage their use. This circular is an official product of the Swift team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24355 SUBJECT: LIGO/Virgo S190426c: Gaia Photometric Alerts transient candidate DATE: 19/04/30 15:20:56 GMT FROM: Zuzanna Kostrzewa-Rutkowska at SRON Z. Kostrzewa-Rutkowska (SRON/RU), S. Hodgkin, A. Delgado, D.L. Harrison, M. van Leeuwen, G. Rixon, A. Yoldas (IoA Cambridge), D. Eappachen, P.G. Jonker (SRON/RU) on behalf of Gaia Alerts team report the discovery of a transient candidate within the probability skymap of S190426c (LIGO/VIRGO Collaboration GCN 24237): --------------------------------------------------------------------------- Name TNSid Date [TCB] RaDeg DecDeg AlertMag URL --------------------------------------------------------------------------- Gaia19bpm AT2019ehs 2019-04-29T07:29:20 299.21327 61.65942 18.86 http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19bpm/ --------------------------------------------------------------------------- Acknowledgements: This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. ZKR, DE, and PGJ acknowledge support from the European Research Council under ERC Consolidator Grant agreement no 647208. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24357 SUBJECT: LIGO/Virgo S190426c: ZTF pre-detections of Gaia19bpm AT2019ehs DATE: 19/04/30 18:36:11 GMT FROM: Igor Andreoni at Caltech Igor Andreoni (Caltech), Eric Bellm (UW) report on behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations We searched for Zwicky Transient Facility (ZTF) detections associated with Gaia19bpm AT2019ehs (Kostrzewa-Rutkowska et al., GCN 24355) in the archive of ZTF alerts.  A transient, dubbed ZTF19aaphkxx, was found at the location of Gaia19bpm.  The transient was first detected in public ZTF data starting from 2019-04-08 (g = 18.66 +- 0.14) and it peaked around 2019-04-15 (g = 17.98 +- 0.08). The optical transient was detected days before the gravitational wave event S190426c (LIGO and Virgo Collaboration, GCN 24237), therefore we exclude an association between Gaia19bpm AT2019ehs and S190426c. ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan; IIT-B, India; IIA, India; LJMU, UK; TTU USA and USyd, Australia. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24359 SUBJECT: LIGO/Virgo S190426c: ZTF19aaslzjf, ZTF19aasmftm and ZTF19aasmddt 1.5m OSN and 10.4m GTC observations DATE: 19/05/01 09:45:01 GMT FROM: Alberto J. Castro-Tirado at IAA-CSIC Y.-D. Hu, A. J. Castro-Tirado, (IAA-CSIC), A. F. Valeev and V. V. Sokolov (SAO-RAS), R. Sanchez-Ramirez (INAF-IAPS), X.-Y. Li, A. Ayala, E. Fernandez-Garcia and F. J. Aceituno (IAA-CSIC), I. Carrasco, A. Castellon and C. Perez del Pulgar (UMA), M. D. Caballero-Garcia (ASU-CAS), S. B. Pandey (ARIES), A. Garcia and S. Geier (GRANTECAN, IAC, ULL), on behalf of a larger collaboration, report: Following the detection of the three new transients ZTF19aaslzjf, ZTF19aasmftm and ZTF19aasmddt (Perley et al., GCN 24331) within the error area of the GW event S190426c (LVC, GCN 24237), we observed the three targets with the 1.5m telescope at the Observatorio de Sierra Nevada (Spain) in the BVI-bands, starting on May 1, 02:01 UT. In addition, optical spectra for each target (1200s) covering the range 3700-7500 A were obtained with the 10.4m GTC telescope equipped with OSIRIS in La Palma (Spain) starting on May 1, 02:30 UT. ZTF19aaslzjf is found to be in the outskirts of its host galaxy and its spectrum is consistent with that of a type Ia SN at z= 0.086. ZTF19aasmftm is found to be in the outskirts of its host galaxy and its spectrum is consistent with that of a type Ia SN few days before maximum at z = 0.156 (confirmed by the emission lines of the galaxy). ZTF19aasmddt is found to be in the outskirts of its host galaxy at a redshift z = 0.028. The spectrum resembles that of a Type II SN at the same redshift before maximum. Therefore none of these three newly reported ZTF transients seem to be related to the GW event S190426c. We acknowledge the excellent support from the GTC staff. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24368 SUBJECT: LIGO/Virgo S190426c: Gaia19boq 0.6m BOOTES-5/JGT, 1.5m OSN and 10.4m GTC observations DATE: 19/05/02 14:38:17 GMT FROM: Alberto J. Castro-Tirado at IAA-CSIC R. Sanchez-Ramirez (INAF-IAPS), A. F. Valeev and V. V. Sokolov (SAO-RAS), Y.-D. Hu, A. J. Castro-Tirado, X.-Y. Li, A. Ayala, E. Fernandez-Garcia and F. J. Aceituno (IAA-CSIC), I. Carrasco, A. Castellon and C. Perez del Pulgar (UMA), D. Hiriart and W. H. Lee (UNAM), S. Jeong and I. H. Park (SKKU), A. Garcia and S. Geier (GRANTECAN, IAC, ULL), on behalf of a larger collaboration, report: Following the detection of Gaia19boq (Kostrzewa-Rutkowska et al., GCN 24344) within the error area of the GW event S190426c (LVC, GCN 24237), we observed the target with the 1.5m telescope at the Observatorio de Sierra Nevada (Spain) in the BVI-bands, starting on May 1, 04:07 UT. Complementary images I ugriZ were taken starting on May 1, 11:41 UT at the 0.6m BOOTES-5/JGT in Observatorio Nacional de San Pedro Martir (Mexico). In addition, an optical spectrum (900s) covering the range 3700-7500 A was obtained with the 10.4m GTC telescope equipped with OSIRIS in La Palma (Spain) starting on May 1, 04:07 UT. The Gaia19boq spectrum reveals strong Balmer lines in absorption, with the exception of a very weak H-alpha showing a P Cyg profile. All lines are redshifted ~400 km/s. Therefore we conclude that Gaia19boq is found to be a CVN star in outburst in our Galaxy and therefore unrelated to the GW event S190426c. We acknowledge the excellent support from the GTC staff. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24411 SUBJECT: LIGO/Virgo S190426c: Update on Source Classification DATE: 19/05/06 16:21:43 GMT FROM: Deep Chatterjee at University of Wisconsin, Milwaukee LIGO/Virgo S190426c: Update on Source Classification The LIGO Scientific Collaboration and Virgo Collaboration report: Based on posterior support from preliminary parameter estimation [1,2], under the assumption that the candidate S190426c is astrophysical in origin, the relative probabilities amongst the signal categories NSBH : MassGap : BNS : BBH are revised to be approximately 12 : 5 : 3 : 0. Under the same assumption of astrophysical origin, we find strong evidence that the lighter compact object has a mass < 3 solar masses (HasNS: >99%) and a 72% probability of having disrupted material outside the final compact object (HasRemnant: 72%). The probability of non-astrophysical origin and the false alarm rate are not being updated at this time; both measures of significance should be expected to change with offline analyses and continued observations. For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo Public Alerts User Guide . [1] Veitch, et al. PRD 91, 042003 (2015) [2] Abbott, et al. PRL 116, 241102 (2016) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24418 SUBJECT: LIGO/Virgo S190426c: Konus-Wind observations DATE: 19/05/07 11:28:17 GMT FROM: Dmitry Svinkin at Ioffe Institute D. Svinkin, S. Golenetskii, R.Aptekar, D. Frederiks, M. Ulanov, A. Tsvetkova, A. Lysenko, A. Kozlova, and T. Cline, on behalf of the Konus-Wind team, report: Konus-Wind (KW) was observing the whole sky at the time of the LIGO/Virgo event S190426c (2019-04-26 15:21:55.337 UTC, hereafter T0; LIGO/Virgo Collaboration GCN Circ. 24237). No triggered KW event happened from ~7 days before and ~0.6 day after T0. The closest waiting-mode event was ~12.5 hours before T0. Using waiting-mode data within the interval T0 +/- 100 s, we found no significant (> 5 sigma) excess over the background in both KW detectors on temporal scales from 2.944 s to 100 s. We estimate an upper limit (90% conf.) on the 20 - 1500 keV fluence to 7.3x10^-7 erg/cm^2 for a burst lasting less than 2.944 s and having a typical KW short GRB spectrum (an exponentially cut off power law with alpha =-0.5 and Ep=500 keV). For a typical long GRB spectrum (the Band function with alpha=-1, beta=-2.5, and Ep=300 keV), the corresponding limiting peak flux is 2.0x10^-7 erg/cm^2/s (20 - 1500 keV, 2.944 s scale). All the quoted values are preliminary. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24420 SUBJECT: LIGO/Virgo S190426c (BHNS candidate): Implications from Numerical Relativity DATE: 19/05/07 18:39:37 GMT FROM: Antonios Tsokaros at U of Illinois,Urbana-Champaign LIGO/Virgo S190426c (BHNS candidate): Implications from Numerical Relativity M. Ruiz, S. L. Shapiro and A. Tsokaros report on behalf of the Illinois Relativity Group Consistent with GCN 24411, indicating that the LIGO/Virgo gravitational wave source S190426c is a likely BHNS, the absence of a gamma-ray burst, kilonova and other counterpart EM radiation agrees with recent GRMHD simulations of BHNS mergers by our Illinois Relativity Group. In Ruiz, Shapiro and Tsokaros (2018), PRD 98, 123017 (arXiv 1810.08618), the group surveyed BHNS configurations with different initial mass ratios q=BH:NS=3:1 and 5:1, BH spins a_{BH}/M_{BH}=-0.5, 0, 0.5, 0.75 and dipole magnetic fields (aligned and tilted by 90 degrees with respect to the orbital angular momentum). Only for initial a_{BH}/M_{BH}>=0.5 and aligned B-fields did we find collimated, magnetically-confined jets launched from the poles of the BH remnants following the peak GW signal. Only in those cases did we find EM luminosities consistent with typical sGRBs and significant mass outflows. For example, in our case q=5:1 and a_{BH}/M_{BH}=0 the remnant disk and magnetic field were too small to drive a jet and generate a significant mass outflow or counterpart EM luminosity, hence no sGRB or kilonova. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24430 SUBJECT: LIGO/Virgo S190426c: Discovery Channel Telescope Follow-Up of ZTF19aassfws DATE: 19/05/09 03:33:11 GMT FROM: Brad Cenko at NASA/GSFC S. B. Cenko (GSFC), S. Frederick (UMd), P. Gatkine (UMd), S. Dichiara (GSFC/UMd), E. Troja (GSFC/UMd), and L. P. Singer (GSFC) report on behalf of a larger collaboration: We obtained a spectrum of the transient source ZTF19aassfws (Perley et al., GCN 24331) with the DeVeny spectrograph on the 4.3m Discovery Channel Telescope beginning at 10:07 UT on 2 May 2019. The slit was centered on the nucleus of the host galaxy, SDSS J195440.25+611424.2. The spectrum is dominated by a red stellar continuum, along with a series of nebular emission lines corresponding to a redshift of z = 0.093. No clear evidence for broad emission lines or non-galaxy features are apparent. For standard cosmological parameters, this corresponds to a luminosity distance of ~ 430 Mpc, consistent with the distance inferred from the gravitational wave emission (LVC et al., GCN 24237). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24433 SUBJECT: LIGO/Virgo S190426c: INT Observations of ZTF19aassfws DATE: 19/05/09 15:13:58 GMT FROM: Mansi M. Kasliwal at Caltech/Carnegie Christoffer Fremling (Caltech), Andrew Levan (Radboud), Mansi Kasliwal (Caltech) and Nial Tanvir (Leicester) report on behalf of a larger collaboration We imaged ZTF19aassfws (Perley et al. GCN 24331, Coughlin et al. GCN 24283) with the INT on UT 2019-04-08. Difference imaging relative to PanSTARRS1 (Chambers et al. 2016) finds no detection in the r-band to r > 22.6 mag and a bright detection in z-band at z ~ 20.8,corresponding to M_Z ~ -17.2 at z=0.093 (Cenko et al. GCN24430). The z-band luminosity is higher than GW170817 at this phase. The red color at this phase is plausible for a kilonova but we cannot definitively rule out unrelated, nuclear activity. We further caution that the INT and PS1 have different filter transmission curves in z-band. We encourage follow-up to confirm or refute the association of this source with the GW event S190426c (LVC et al. GCN 24237, GCN 24411). We thank the INT observers, Lord Dover and Tarik Zegmott for facilitating these observations. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24434 SUBJECT: LIGO/Virgo S190426c: Correction to typo in GCN 24433 DATE: 19/05/09 17:24:17 GMT FROM: Mansi M. Kasliwal at Caltech/Carnegie The correct UT date for the INT observations reported in Fremling et al. GCN 24433 is 2019-05-08. Apologies for the typo. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24440 SUBJECT: LIGO/Virgo S190426c: Archival VLASS Observations of ZTF19aassfws 14 days prior to Merger DATE: 19/05/10 05:47:43 GMT FROM: Gregg Hallinan at OVRO-LWA Dillon Dong (Caltech), Gregg Hallinan (Caltech), Dale Frail (NRAO) and Kunal Mooley (NRAO/Caltech) report: The VLA Sky Survey observed a field containing the nuclear optical transient ZTF19aassfws (Perley et al., GCN 24331) on 2019-04-12 at UT 14:16:53, 14 days prior to the compact object merger candidate S190426c (LVC et al.; GCN 24237). There is no archival 3GHz source at the transient location, with a local 3 sigma upper limit of 390uJy. This rules out a radio-luminous AGN with a specific luminosity greater than 9x10^28 erg/s/Hz at the spectroscopic redshift reported by Cenko (GCN 24430). The VLA Sky Survey (VLASS) is a multi-epoch, 2-4 GHz survey with the Karl G. Jansky Very Large Array (VLA) covering the full sky north of declination = -40 degrees at ~2.5" resolution to a 1-sigma depth of ~120uJy/beam per epoch. Observations and data reduction for the VLASS are carried out by staff of the National Radio Astronomy Observatory (NRAO). The NRAO is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24458 SUBJECT: LIGO-Virgo S190426c: Pan-STARRS non-detection of ZTF19aassfws DATE: 19/05/10 17:55:38 GMT FROM: Stephen Smartt at Queen's U/Belfast M. Huber, (IfA), S. J. Smartt (QUB), K. Chamber (IfA) K. W. Smith, D. R. Young, O. McBrien, J. Gillanders. S. Srivastav, S. J. Smartt, D. O'Neil, P. Clark, S. Sim (QUB), T. de Boer, J. Bulger, J. Fairlamb, C.-C. Lin, T. Lowe, E. Magnier A. Schultz, R. J. Wainscoat, M. Willman (IfA, University of Hawaii) We imaged ZTF19aassfws (Fremling et al. GCN 24433, Cenko et al. GCN 24430, Perley et al. GCN 24331, Coughlin et al. GCN 24283) with Pan-STARRS1 on UT 2019-05-09. This is the ZTF candidate within the skymap and distance range of s190426c (the possible NS-BH candidate), which was detected at r=21.41. A set of 6x300s exposures in i and z band filters were taken and stacked together. A custom made reference image in each filter was constructed (deeper than the public 3Pi stack of Chambers et al. 2016, arXiv:1612.05560) and subtracted this from the night stacks. The image quality was 0.75 arcseconds in the stacked frames. We find no clear detection of significant excess flux at the positon of ZTF19aassfws, or at the core of the host galaxy in either band. There is some residual positive flux coincident with the galaxy core in each filter but this is not PSF in shape and is almost certainly a minor residual from the convolution and subtraction. Forcing photometry at the positon we find i =23.5 +/- 0.5 and z=22.5 +/- 0.3. We do not consider either to be significant detections and conclude there is no transient flux above these estimates. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24486 SUBJECT: LIGO/Virgo S190426c: VLA Follow-Up Observations of ZTF19aassfws DATE: 19/05/11 16:52:35 GMT FROM: Alessandra Corsi at Texas Tech U Alessandra Corsi (TTU), Dale Frail (NRAO), Gregg Hallinan (Caltech), Kunal Mooley (Caltech/NRAO), Mansi Kasliwal (Caltech) report on behalf of the JAGWAR collaboration: We imaged the field of ZTF19aassfws (Perley et al. GCN 24331, Cenko et al. GCN 24430, Fremling et al. GCN 24433, Dong et al. 24440, Huber et al. GCN 24458), identified in the error region of the LIGO-Virgo event S190426c (LVC GCN 24237, 24411), with the Karl G. Jansky Very Large Array (VLA) in its B configuration. Our observations started on 2019 May10 at 07:19:15 UT, ended on 2019 May 10 at 10:18:45 UT, and were carried out at a central frequency of about 2.8 GHz. Preliminary analysis shows no evidence for significant radio emission at the location of ZTF19aassfws. We thus constrain the radio flux density at the location of the ZTF transient to be <~16 uJy (3 sigma). At z=0.093, this corresponds to a luminosity density <~3.5e27 erg/s/Hz. We thank the NRAO staff for promptly executing these observations. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24551 SUBJECT: LIGO/Virgo S190426c: AMI-LA radio observations of ZTF19aassfws DATE: 19/05/15 10:10:21 GMT FROM: Lauren Rhodes at Oxford L. Rhodes, R. Fender, D. Williams, J. Bright (Oxford), K. Mooley (NRAO, Caltech; Jansky Fellow), A. Horesh (The Hebrew University of Jerusalem), D. Green, D. Titterington (MRAO) and the JAGWAR collaboration. We observed the position of the reported GW190426c afterglow candidate: ZTF19aassfws (D. A. Perley et al. GCN 24331) with the AMI Large Array at a central frequency of 15.5GHz. We started observing on 2019 May 10.16 for 4 hrs. We find no significant radio emission at the coordinates of ZTF19aassfws and therefore report a 3 sigma upper limit of 177uJy. We thank the MRAO staff for scheduling these observations. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24592 SUBJECT: LIGO/Virgo S190426c: NICER X-ray Follow-Up of ZTF19aassfws DATE: 19/05/19 02:37:16 GMT FROM: Dheeraj R. Pasham at Mass. Inst. of Technology Dheeraj Pasham (MIT), Keith Gendreau (NASA/GSFC), Zaven Arzoumanian (NASA/GSFC), Stephen Eikenberry (UFL), Wynn C.G. Ho (Haverford) report on behalf of the NICER team: The transient ZTF19aassfws (Perley et al., GCN#24331) fell in the LIGO/Virgo error box of the trigger S190426c (LVC et al., GCN#24237), and Cenko et al. (GCN#24430) found that its distance is consistent with that inferred from the gravitational wave signal. NICER observed this target for 7 ks, approximately half of which was in especially low background/high sensitivity conditions. We do not detect any X-ray emission above the background from this region. Assuming an X-ray spectrum with a power-law index of 1.7 (similar to GW170817) at a redshift of 0.093 with an absorbing column of 8e20 cm**-2 (Milky Way column), we estimate an upper limit on the unabsorbed 0.35-11.5 keV X-ray flux of 1.3e-13 erg/s/cm**2. NICER can carry out prompt follow-up observations of transients and is planning to systematically follow up alerts from LIGO/Virgo and other X-ray bright extra-galactic transients in the future. NICER is a 0.2-12 keV X-ray telescope operating on the International Space Station. The NICER mission and portions of the NICER science team activities are funded by NASA. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24863 SUBJECT: LIGO/Virgo S190426c: Swift UVOT - no new counterpart candidates identified DATE: 19/06/20 13:55:26 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (UCL-MSSL), A. A. Breeveld (MSSL-UCL), C. Gronwall (PSU), F. E. Marshall (NASA/GSFC), S. R. Oates (Uni. of Warwick), M.J. Page (UCL-MSSL), M. de Pasquale (Istambul U), M. H. Siegel (PSU), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), S. D. Barthelmy (NASA/GSFC), A. P. Beardmore (U. Leicester), D. N. Burrows (PSU), S. Campana (INAF-OAB), S. B. Cenko (NASA/GSFC), G. Cusumano (INAF-IASF PA), V. D'Elia(ASDC), P. A. Evans (U. Leicester), P. Giommi (ASI), D. Hartmann (Clemson U.), J. A. Kennea (PSU), H. A. Krimm (NSF), A. Y. Lien (GSFC/UMBC), D. B. Malesani (DTU Space), A. Melandri (INAF-OAB), J. A. Nousek (PSU), P. T. O'Brien (U. Leicester), J. P. Osborne (U. Leicester), C. Pagani (U. Leicester), K. L. Page (U.Leicester), D.M. Palmer (LANL), M. Perri (ASDC), J. L. Racusin (NASA/GSFC), T. Sakamoto (AGU), B. Sbarufatti (INAF-OAB/PSU), G. Tagliaferri (INAF-OAB), A. Tohuvavohu (PSU), and E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team: The Swift UVOT instrument started follow up observations of the LIGO-Virgo event S190426c (LVC GCN Circ. No. 24237) at 2019-04-26 17:45:00 UT 142 minutes after the event. Observations continued for about 48 hours (Tohuvavohu et al., GCN Circ. No. 24353). The UVOT approach for searching for the ultraviolet-optical counterpart has been described in Kuin et al. (GCN Circ. No. 24767). The limiting magnitude can vary but typically is 18.6th magnitude (Vega). In the 894 fields that were observed, UVOT detected 1008 galaxies and 130 counterpart candidates but none of the counterpart candidates from the automated processing proved to be a viable source. Neither did the additional inspection of the imaged galaxies lead to a candidate missed by the automated processing. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25549 SUBJECT: LIGO/Virgo S190426c: Update on Probability of Terrestrial Origin DATE: 19/08/29 14:46:43 GMT FROM: Deep Chatterjee at University of Wisconsin, Milwaukee The LIGO Scientific Collaboration and Virgo Collaboration report: A revised computation of the classification of the candidate based on detection-pipeline-specific foreground and background models is available. The probability of the source being of terrestrial origin is now estimated to be 58% in contrast to the original estimation of 14% in  GCN Circular 24237. This revision was necessitated by a bug-fix in the source-classification code. This same bug-fix was used to update the event candidate S190510g, as reported in GCN Circular 24462. We apologize for the delay in updating the information for this event. The estimated false alarm rate is unchanged at 1.9e-08 Hz, or about one per 1.6 years. Note that future offline analyses may infer a different terrestrial probability and/or false alarm rate. The new p_astro.json file in GraceDB at https://gracedb.ligo.org/superevents/S190426c/ reports that the revised classification of the candidate is Terrestrial (58%), BNS (24%), MassGap (12%), NSBH (6%) and BBH (<1%). Note that the parameter estimation based classification reported in GCN Circular 24411 is unchanged: Assuming that the candidate S190426c is astrophysical in origin, the relative probabilities amongst the signal categories NSBH : MassGap : BNS : BBH are approximately 12 : 5 : 3 : 0 based on posterior support.