//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24063 SUBJECT: LIGO-Virgo S190408an: AGILE MCAL observations DATE: 19/04/08 20:42:39 GMT FROM: Fabrizio Lucarelli at SSDC/INAF-OAR F. Lucarelli (SSDC, and INAF/OAR), A. Ursi (INAF/IAPS), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), M. Cardillo, C. Casentini, G. Piano, C. Pittori, F. Verrecchia (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 S190408an at T0 = 2019-04-08 18:18:02 (UT), a preliminary analysis of the AGILE MiniCalorimeter (MCAL) data found no event candidates within a time interval covering -15 / + 8 sec from the LIGO-Virgo T0. Two-sigma upper limits (ULs) are obtained for a 1 s integration time at different celestial positions within the accessible S190408an localization region, from a minimum of 1.3E-06 erg cm^-2 to a maximum of 2.2E-06 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: 24064 SUBJECT: LIGO-Virgo GW S190408an: J-GEM optical/NIR follow-up observations DATE: 19/04/08 20:58:09 GMT FROM: Katsuhiro L. Murata at Nagoya U Murata, K. L. (Tokyo Tech), Sasada, M., Nakaoka, T. (Hiroshima U.), Morokuma, T. (U. of Tokyo), and Utsumi, Y. (Stanford U./SLAC), on behalf of J-GEM collaboration Right after receiving the first gravitational wave alert, S190408an, in the observing run 3 (O3), we conducted optical and near-infrared imaging observations of 7 nearby galaxies (see a table below) within the probability skymap of S190408an with - 50 cm MITSuME telescope at Akeno Observatory using a 3 color imager in g’, Rc, Ic - 50 cm MITSuME telescope at Okayama Astrophysical Observatory using a 3 color imager in g’, Rc, Ic - Kanata 150 cm telescope at Higashi-Hiroshima Observatory using HONIR -- a 2 color imager in Rc and H (Sakimoto et al. 2012, SPIE, 8846, 884673; Akitaya et al. 2014, 9147, 91474O; Ui et al. 2014, 9147, 91476C) We also performed blind imaging survey over 260 deg2 using Tomo-e Gozen camera on the 105-cm Kiso Schmidt telescope which is a very wide-field (20 deg2 field-of-view) optical CMOS imager (Sako et al. 2018, SPIE, 10702, 107020J). Data reduction is in progress. name RA Dec GL221849+205045 334.7061 20.846 GL231817+515551 349.572 51.9309 GL225419+384152 343.5806 38.6978 GL225746+424819 344.4403 42.8053 GL222235+224327 35.6449 22.7242 GL222437+203049 336.153 20.5135 GL184632-384819 281.6345 -38.8053 These observations were done in the framework of J-GEM collaboration (Morokuma et al. 2016, PASJ, 68, 9L). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24065 SUBJECT: LIGO/Virgo S190408an: Fermi GBM Observation DATE: 19/04/08 21:00:15 GMT FROM: C. Michelle Hui at MSFC/Fermi-GBM C. M. Hui (NASA/MSFC) reports on behalf of the Fermi-GBM Team and the GBM+LIGO/Virgo Working Group: At the time of S190408an, Fermi was passing through the South Atlantic Anomaly from 14 minutes prior to 15 minutes after the trigger time; therefore the GBM detectors were disabled. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24066 SUBJECT: INTEGRAL observation of S190408an DATE: 19/04/08 21:04:49 GMT FROM: Volodymyr Savchenko at ISDC,U of Geneve Volodymyr Savchenko, Carlo Ferrigno  (ISDC/UniGE, Switzerland) James Rodi,  (IAPS-Roma, Italy) Sandro Mereghetti (INAF IASF-Milano, Italy) on behalf of the INTEGRAL multi-messenger collaboration: https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration Using INTEGRAL we have performed a search for a prompt gamma-ray counterpart of S190408an. At the time of the event (2019-04-08 18:18:02.29 UTC, hereafter T0), INTEGRAL was operating in nominal mode. The peak of the event localization probability was at an angle of 115 deg with respect to the spacecraft pointing axis. This orientation implies strongly suppressed response of IBIS, strongly suppressed response of IBIS/Veto, and somewhat suppressed response of SPI-ACS. The background within +/-300 seconds around the event was very stable. We do not detect any significant counterparts and estimate a 3-sigma upper limit on the 75-2000 keV fluence of 2.5e-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 ~2.1e-07 (8.1e-08) erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24067 SUBJECT: LIGO-Virgo S190408an: HAWC follow-up DATE: 19/04/08 21:08:25 GMT FROM: Israel Martinez-Castellanos at UMD/HAWC I. Martinez-Castellanos (University of Maryland, College Park) report on behalf of the HAWC Collaboration: The HAWC Collaboration performed a follow-up of the gravitational wave trigger S190408an. At the time of the trigger the HAWC local zenith was oriented toward (α, δ) = (13.9°, 19.0°). 80% of the GW candidate sky location probability fell within our observable field (0-45 deg zenith angle). We performed a search for a short timescale emission using 6 sliding time windows (dt = 0.3s, 1s, 3s, 10, 30s and 100s), shifted forward in time by 20% of their width. We searched 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 steady-state cosmic-ray background was observed. The sensitivity of this analysis is greatly dependent on energy and zenith angle. For reference, it has a 5sigma detection sensitivity to a 1s (100s) burst with a fluence of 3x10^-7 erg/cm^2 to 2x10^-5 erg/cm^2 (2x10^-6 erg/cm^2 to 8x10^-5 erg/cm^2) in the 0.3-1TeV energy range, 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 ~0.3-100TeV, and monitors 2/3 of the sky every day with an instantaneous field-of-view of ~2 sr. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24068 SUBJECT: Search for neutrino counterparts to GW candidate S190408an with IceCube DATE: 19/04/08 21:14:21 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 GW candidate S190408an (https://gcn.gsfc.nasa.gov/notices_l/S190408an.lvc) in a time range of 1000 seconds centered on the alert event time (2019-04-08 18:09:42.288 UTC to 2019-04-08 18:26:22.288 UTC) during which IceCube was collecting good quality data. No track-like events are found in spatial coincidence with the 90% spatial containment of S190408an calculated from the map circulated in the initial notice. IceCube's sensitivity to point sources within the location spanned by the 90% spatial containment of S190408an ranges from 0.029 to 0.606 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: 24069 SUBJECT: LIGO/Virgo S190408an: Identification of a GW binary merger candidate DATE: 19/04/08 21:36:11 GMT FROM: Leo Singer at GSFC The LIGO Scientific Collaboration and the Virgo Collaboration report: We identified the compact binary merger candidate S190408an during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-04-08 18:18:02.288 UTC (GPS time: 1238782700.288). The candidate was found by the GstLAL [1], SPIIR [2], CWB [3], MBTAOnline [4], and PyCBC Live [5] analysis pipelines. S190408an is a candidate of interest because its false alarm rate, as determined by the online analysis, is less than one in 100 years. The candidate's properties can be found at this URL: https://gracedb.ligo.org/superevents/S190408an The classification of the signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), BNS (<1%), NSBH (<1%), or MassGap (<1%). Assuming the candidate is astrophysical in origin, there is strong evidence against the lighter compact object having a mass < 3 solar masses (HasNS: <1%). Using the masses and spins inferred from the signal, there is evidence against matter outside the final compact object(HasRemnant: 12%). We believe that the latter quantity (HasRemnant) may be overestimated; we are reviewing it and will provide an update when available. One skymap is available at this time and can be retrieved from the GraceDB candidate page: * bayestar.fits.gz, a preliminary localization generated by BAYESTAR [6], distributed via GCN notice about 34 minutes after the candidate. For the bayestar.fits.gz skymap, the 90% credible region is 387 deg2. Marginalized over the whole sky, the luminosity distance estimate is 1473 +/- 358 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] Hooper et al. PRD 86, 024012 (2012) [3] Klimenko et al. PRD 93, 042004 (2016) [4] Adams et al. CQG 33, 175012 (2016) [5] Nitz et al. PRD 98, 024050 (2018) [6] Singer & Price PRD 93, 024013 (2016) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24070 SUBJECT: LIGO/Virgo S190408an: MASTER Global Robotic Net optical observations DATE: 19/04/08 22:44:58 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, T.Pogrosheva, E. Gorbovskoy, N.Tyurina, V.Kornilov, D.Vlasenko, V.Vladimirov, D.Zimnukhov, A.Kuznetsov, P.Balanutsa, I.Gorbunov, A. Chasovnikov, V.Topolev, V.Grinshpun, F.Balakin, K.Zhirkov, D.Kuvshinov, A.Pozdnyakov (Lomonosov Moscow State University, SAI, Physics Department), 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) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O. Gress, N.M. Budnev, O.Ershova (Applied Physics Institute, Irkutsk State University), V. Yurkov, A. Gabovich, Yu. Sergienko, D. Kobcev (Blagoveschensk Educational State 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) automatically started inspect of the LIGO/Virgo S190408an error-box after receiving probability map. MASTER synchronousely observed central part of LIGO/Virgo S190408an error-box during own survey (at alert time). Reduction and observation will be cntinued. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24071 SUBJECT: LIGO-Virgo S190408an: AGILE GRID observations DATE: 19/04/09 00:14:47 GMT FROM: Fabrizio Lucarelli at SSDC/INAF-OAR F. Lucarelli, C. Pittori, F. Verrecchia (SSDC, and INAF/OAR), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), M. Cardillo, C. Casentini, G. Piano, A. Ursi (INAF/IAPS), 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 trigger event S190408an at T0 = 2019-04-08 18:18:02 (UT) (GCN #24069) we performed an analysis of the AGILE Gamma-Ray Imaging Detector (GRID) data. At LIGO/Virgo trigger time (T0) the GRID exposure did not optimally cover the LIGO/Virgo localization region. An analysis of the data in the energy range 30 MeV - 10 GeV was performed over the time intervals T0-300s -- T0-200s, where full coverage of the majority of the localisation region was reached. Preliminary values of 3-sigma upper limits (UL) obtained within the accessible LIGO/Virgo 90% c.l. localization region over this time interval are in the range: from 2.0e-07 to 6.5e-07 erg cm^-2 s^-1 for an integration time of 100s. For an integration time of 200s which includes T0, preliminary 3-sigma ULs are in the range: from 5.0e-08 to 3.0e-07 erg cm^-2 s^-1, with a lower localization region coverage of about 80%. 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: 24074 SUBJECT: LIGO/Virgo S190408an: KMTNet observation DATE: 19/04/09 02:56:24 GMT FROM: Myungshin Im at Seoul Nat U Myungshin Im (SNU), Joonho Kim (SNU), Gregory S. H. Paek (SNU), Sungyong Hwang (SNU), Sophia Kim (SNU), Changsu Choi (SNU), Gu Lim (SNU), Chung-Uk Lee (KASI), Seung-Lee Kim (KASI), Hyung Mok Lee (KASI), on behalf of a larger collaboration We performed the search for the EM counterpart of S190408an (Singer et al. GCN 24069) using the KMTNet telescopes, covering about 30 deg^2 area that encompasses the highest confidence regions observable from the southern hemisphere. The observation at the South Africa site has been completed, and the observations are scheduled at the Chile and Australia sites. The central coordinate of each 2 deg x 2deg pointing is given below. G329243-0-0(R) 14:51:33.7 -41:24:41 B,R 120 G329243-1-0(R) 14:43:33.8 -41:24:41 B,R 120 G329243-2-0(R) 14:59:33.7 -41:24:41 B,R 120 G329243-3-0(R) 14:51:33.7 -39:24:41 B,R 120 G329243-4-0(R) 14:51:33.7 -43:24:41 B,R 120 G329243-5-0(R) 14:43:33.8 -39:24:41 B,R 120 G329243-6-0(R) 14:59:33.7 -43:24:41 B,R 120 G329243-7-0(R) 14:43:33.8 -43:24:41 B,R 120 The observations and the analysis of the data are ongoing. We thank the observers at the KMTNet sites for performing the observation. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24075 SUBJECT: LIGO/Virgo S190408an: Swift/BAT data search DATE: 19/04/09 04:16:05 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), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), 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 S190408an (LIGO/VIRGO Collaboration GCN Circ. 24069), where T0 is the LVC trigger time (2019-04-08T18:18:02.288 UTC). The center of the BAT FOV at T0 is RA = 133.644 deg, DEC = 20.099 deg, ROLL = 291.895 deg. The BAT Field of View (>10% partial coding) covers 0.02% of the integrated LVC localization probability. 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, respectively. 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 ~ 1.49 x 10^-6 erg/s/cm^2. BAT retains decreased, but significant, sensitivity to rate increases for gamma-ray events outside of its FOV. About 9.37% 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 of those within the FOV. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24076 SUBJECT: LIGO/Virgo S190408an: MASTER OT detection DATE: 19/04/09 07:58:43 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, T.Pogrosheva, E. Gorbovskoy, N.Tyurina, V.Kornilov, D.Vlasenko, V.Vladimirov, D.Zimnukhov, A.Kuznetsov, P.Balanutsa, I.Gorbunov, A. Chasovnikov, V.Grinshpun, F.Balakin (Lomonosov Moscow State University, SAI, Physics Department), 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) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O. Gress, N.M. Budnev, O.Ershova (Applied Physics Institute, Irkutsk State 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) during LIGO/Virgo S190408an (Singer et al. GCN 24069) South Part Error Field Inspection (Lipunov et al. GCN 24070) at MASTER-OAFA found optical transient (no known sources in VIZIER database inside 5") MASTER OT J140518.22-395309.9 discovery MASTER auto-detection system discovered OT source at (RA,Dec2000) = 14h 05m 18.22s -39d 53m 09.9s on 2019-04-09.07809UT. The OT unfiltered magnitude is 17.4m (mlim=19.1m). The OT is seen in 2 MASTER LVC inspect images (Pogrosheva et a., ATel #12644). There is no minor planet at this place. We have reference image without OT on 2018-05-19.13417 UT with 20.2 unfiltered magnitude limit. There is no any sources in VIZIER database. Spectral observations are required. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/140518.22-395309.9.png MASTER cover map of Ligo/Virgo S190408an error-field inspection will be available on-line at: http://master.sai.msu.ru/static/LVC/MASTER_S190408an_map.jpg Reduction and observation will be cntinued. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24077 SUBJECT: LIGO/Virgo S190408an: Insight-HXMT/HE observation DATE: 19/04/09 08:57:23 GMT FROM: Ce Cai at IHEP Q. Luo, C. Cai, 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=2019-04-08 18:18:02.288 UTC). At T0, the LIGO-Virgo localization region was fully covered by the Insight-HXMT without occultation by the Earth. Within T0 ± 100 s, no significant excess events (SNR > 5 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: 1.6e-08 erg cm^-2 10s: 5.3e-08 erg cm^-2 Band model 2 (alpha=-1.0, beta=-2.3, Ep=230 keV): 1s: 2.6e-08 erg cm^-2 10s: 8.7e-08 erg cm^-2 Band model 3 (alpha=-0.0, beta=-1.5, Ep=1000 keV): 1s: 7.1e-08 erg cm^-2 10s: 2.9e-07 erg cm^-2 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: 24078 SUBJECT: LIGO/Virgo S190408an: MASTER OT is 27 day old ATLAS SN candidate and unrelated DATE: 19/04/09 09:08:52 GMT FROM: Stephen Smartt at Queen's U/Belfast S. J. Smartt, K. W. Smith, D. R. Young, O. McBrien, J. Gillanders. S. Srivastav, D. O’Neil, P. Clark, S. Sim (QUB), L. Denneau, H. Flewelling, A. Heinze, J. Tonry, H. Weiland K. C. Chambers , M. Huber, E. Magnier, A. Schultz, (IfA, Univ. Hawaii), A. Rest (STScI), B. Stalder (LSST), C. Stubbs (Harvard) Lipunov et al (GCN 24076) reported the discovery of an optical transient MASTER OT J140518.22-395309.9 close to the southern part of the skymap of LIGO/Virgo source S190408an. The ATLAS survey (Tonry et al. 2018, Stalder et al. 2016) has detected this source since MJD=58555 (2019-03-13) at o = 17.4. It peaked around MJD=58569 at o = 17 and has a SN like lightcurve. There is no obvious catalogued host galaxy. In summary, we confirm the discovery of MASTER that this is a real optical transient (with no host galaxy) at coordinates : 14:05:18.21 -39:53:10.0 211.32588 -39.88612 But that it is almost certainly a foreground SN about 1 month old, and very unlikely to be related to LIGO/Virgo S190408an. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24079 SUBJECT: LIGO/Virgo S190408an: SAGUARO follow-up observations DATE: 19/04/09 13:40:54 GMT FROM: Michael J. Lundquist at University of Arizona Michael J. Lundquist (UA), Kerry Paterson, Wen-fai Fong (Northwestern), David J. Sand (UA), Stefano Valenti (UC Davis), Sheng Yang (INAF-OAPd, UC Davis), Sam Wyatt (UA), Eric Christensen, Alex Gibbs, Frank Shelly (UA/LPL) report: We initiated observations of 3 fields (each 2.26 x 2.26 deg^2) within the LVC localization region for the GW trigger S190408an (GCN Circ 24069) starting on 2019-04-09 at 11:45 UT. SAGUARO* uses the 1.5m Catalina Sky Survey telescope on Mt. Lemmon, AZ and its 5 deg^2 imager to tile the highest probability regions of the LVC localization that are accessible from southern Arizona in order to search for electromagnetic counterparts to gravitational wave events. The typical limiting magnitudes of single pointings are G~21 mag (calibrated to Gaia DR2). Below are the field centers observed. RA DEC 350.4255 56.3125 354.2550 56.3125 349.7730 58.5208 Any interesting transient candidates will be reported as soon as possible. *SAGUARO stands for Searches After Gravitational-waves Using ARizona's Observatories. It is a partnership between the University of Arizona and Northwestern University. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24080 SUBJECT: LIGO-Virgo S190408an: further AGILE GRID observations after T0 DATE: 19/04/09 13:56:45 GMT FROM: Fabrizio Lucarelli at SSDC/INAF-OAR F. Lucarelli, C. Pittori, F. Verrecchia (SSDC, and INAF/OAR), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), M. Cardillo, C. Casentini, G. Piano, A. Ursi (INAF/IAPS), 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 trigger event S190408an at T0 = 2019-04-08 18:18:02 (UT) (GCN #24069) we performed a further analysis of the AGILE Gamma-Ray Imaging Detector (GRID) data after the trigger time. An analysis of the data in the energy range 30 MeV - 10 GeV was performed over the time interval T0+200s -- T0+300s, where full coverage of the majority of the localisation region (>95%) was reached. Preliminary GRID values of 3-sigma upper limits (UL) obtained within the accessible LIGO/Virgo 90% c.l. localization region over this time interval are in the range: from 2.5e-07 to 3.5e-07 erg cm^-2 s^-1 for an integration time of 100s. These UL values are compatible with those obtained for an integration time of 100s before T0, and reported in the previous AGILE GRID GCN #24071. These measurements were obtained with AGILE observing a large portion of the sky in spinning mode. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24082 SUBJECT: LIGO/Virgo ST190408an: Fermi-LAT search for a high-energy gamma-ray counterpart DATE: 19/04/09 16:22:30 GMT FROM: Makoto Arimoto at Tokyo Inst of Tech N. Omodei (Stanford Univ.), F. Longo (University and INFN Trieste), M. Arimoto (Kanazawa Univ.), and E. Bissaldi (Politecnico & INFN Bari) report on behalf of the Fermi-LAT Collaboration: We have searched data collected by the Fermi Large Area Telescope (LAT) for possible high-energy (E > 100 MeV) gamma-ray emission in spatial/temporal coincidence with the LIGO/Virgo trigger ST190408an (Singer et al GCN24069). The Fermi Gamma-ray Space Telescope was passing through the South Atlantic Anomaly (SAA) at the time of the trigger (T0 = 2019-04-08 18:18:02.288 UTC). During SAA passages the LAT does not collect data due to the high charged particle background in this region. The LAT resumed data taking upon exiting the SAA at roughly T0 + 1000 s. At that time the instantaneous coverage of the LIGO map was ~5%, and reached 100% cumulative coverage within ~3 ks. 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 time, and "cumulative coverage" as the integral of the instantaneous coverage over time. We performed a search for a transient counterpart within the 90% contour of LIGO map in the time window from T0 to T0 + 10 ks, and no significant new sources are found. We also performed a search which adapted the time interval of the analysis to the exposure of each region of the sky. No significant candidate counterpart was found. Energy flux upper bounds between 100 MeV and 100 GeV for this search vary between 2e-10 and 7e-10 [erg/cm^2/s]. The Fermi-LAT point of contact for this event is Elisabetta Bissaldi (Elisabetta.Bissaldi@ba.infn.it). 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: 24084 SUBJECT: LIGO/Virgo S190408an: MASTER 3 OT's more detection DATE: 19/04/09 17:17:17 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, T.Pogrosheva, E. Gorbovskoy, N.Tyurina, V.Kornilov, D.Vlasenko, V.Vladimirov, D.Zimnukhov, A.Kuznetsov, P.Balanutsa, I.Gorbunov, F.Balakin, A. Chasovnikov, V.Grinshpun, K.Zhirkov, A.Pozdnyakov, V.Topolev, T.Pogrosheva, V.Shumkov (Lomonosov Moscow State University, SAI, Physics Department), 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) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O. Gress, N.M. Budnev, O.Ershova (Applied Physics Institute, Irkutsk State 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), First of all, we must to say that all this OT's not connected with gravitational wave source, because real BBH can not produce detectable electromgnetic emission. MASTER Global Robotic Net (http://observ.pereplet.ru, Lipunov et al., 2010,Advances in Astronomy,vol. 2010, 30L) during LIGO/Virgo S190408an (Singer et al. GCN 24069) inspection (Lipunov et al. GCN 24070, GCN 24076) detected the following optical transients 1) MASTER OT J154209.55-431742.2 discovery - OT, no any sources in VIZIER, ampl>5m MASTER-OAFA auto-detection system Lipunov et al., "MASTER Global Robotic Net",Advances in Astronomy, 2010, 30L discovered OT source at (RA, Dec) = 15h 42m 09.55s -43d 17m 42.2s on 2019-04-09.06495 UT. The OT unfiltered magnitude is 17.0m (mlim=17.9m). The OT is seen in both 2 LVC inspect images (south part). There is no minor planet at this place. We have reference image without OT on 2017-03-30.32611 UT with 18.6 unfiltered magnitude limit . There is no any sources in VIZIER, it means 22m POSS limit in history and more then 5m of current outburst amplitude (MASTER W=0.2B+0.8R by thousands USNO-B1 field stars) Spectral observations are required. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/154209.55-431742.2.png 2) MASTER OT J231043.63+470956.4 discovery - OT with ampl>7.1m MASTER-Tavrida auto-detection system discovered OT source at (RA, Dec) = 23h 10m 43.63s +47d 09m 56.4s on 2019-04-09.00417 UT. The OT unfiltered magnitude is 14.9m (limit 18.9m). The OT is seen in 8 images. There is no sources in POSS images, it gives more then 7.1mag of current outburst amplitude. There is PanSTARR source in 4.6", but it's too far for error of localization. We have reference image without OT on 2019-03-18.10164 UT with unfiltered magnitude limit 18.7m. Spectral observations are required. The discovery and reference images are available at http://observ.pereplet.ru/images/MASTEROTJ231043.63+470956.4.jpg 3) MASTER OT J140518.22-395309.9 discovery (Lipunov et al. GCN24076) also detected by ATLAS (Smart et al. GCN 24078) in March MASTER cover map of Ligo/Virgo S190408an error-field inspection will be available on-line at: http://master.sai.msu.ru/static/LVC/MASTER_S190408an_map.jpg Reduction and observation will be cntinued. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24086 SUBJECT: LIGO/Virgo S190408an: DDOTI/OAN Optical Observations DATE: 19/04/10 02:04:51 GMT FROM: Alan M Watson at UNAM Alan M. Watson (UNAM), Eleonora Troja (GSFC/UMD), Nat Butler (ASU), 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 the region of maximum probability of the LIGO/Virgo candidate S190408an with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx). We observed a region of approximately 11 degrees in declination by 7 degrees in RA centered on 23:26:00 +54:46:00 2000 from 2019-04-09 11:03 UTC to 12:08 UTC (16.8 to 17.8 hours after trigger) obtaining a total of 42 minutes exposure in the w filter at high airmass. Analysis is ongoing and interesting transient source will be reported later. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24087 SUBJECT: LIGO/Virgo S190408an: TMTS Optical Observation DATE: 19/04/10 11:14:08 GMT FROM: Xiaofeng Wang at Tsinghua University Jun Mo, Wen-xiong Li, Xiao-feng Wang (THU), Xiao-Jun Jiang, Jie Zheng, Xiao-ming Zhang,Tian-meng Zhang (NAOC), Xing-han Zhang, Li-Ming Rui, Dan-feng Xiang, Zhi-hao Chen, Gao-bo Xi, Han Lin, Ji-cheng Zhang, Wei-li Lin, Cheng Miao (THU), Sheng-yu Yan (GU/THU), Ju-jia Zhang (YNAO), and Li-fan Wang (TAMU/PMO) report: We conducted optical imaging observations for gravitational wave alert S190408an (Singer et al. GCN 24069) with 4 x 40 cm Tsinghua Ma-huateng Telescopes (TMTS) at Xinglong Observatory in Hebei Province, China (40.40° N, 117.58° E). Our observations started at 2019-04-09 19:37 UT and ended at 2019-04-09 20:20 UT, covering about 90% credible region of S190408an observable from Xinglong. The total sky area scanned by the TMTS is about 450 deg^2, with each exposure covering the field of view of about 18 deg^2. Our 3σ detection limit is ~19.5 mag for 60s explosure. The center coordinates of our observations are listed below. ----------- ------------- RA(hmd) DEC(dms) 22:20:04.00 +38:00:00.00 22:36:23.87 +42:00:00.00 22:38:56.48 +46:00:00.00 23:01:58.45 +46:00:00.00 22:49:02.22 +50:00:00.00 23:13:55.71 +50:00:00.00 23:38:49.20 +50:00:00.00 23:08:15.72 +54:00:00.00 23:35:28.97 +54:00:00.00 23:08:53.45 +58:00:00.00 23:39:05.05 +58:00:00.00 00:00:00.00 +62:00:00.00 00:34:04.85 +62:00:00.00 23:17:18.93 +62:00:00.00 23:51:23.79 +62:00:00.00 00:00:00.00 +66:00:00.00 00:39:20.25 +66:00:00.00 01:18:40.50 +66:00:00.00 00:00:00.00 +70:00:00.00 00:46:46.85 +70:00:00.00 01:33:33.70 +70:00:00.00 00:00:00.00 +74:00:00.00 00:58:02.84 +74:00:00.00 01:56:05.67 +74:00:00.00 01:16:57.35 +78:00:00.00 02:33:54.69 +78:00:00.00 ------------ ------------- Detailed data analysis is still in progress and any interesting transients will be reported later. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24088 SUBJECT: LIGO/Virgo S190408an: CALET Observations DATE: 19/04/10 11:14:51 GMT FROM: Takanori Sakamoto at AGU S. Torii (Waseda U), A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU), Y. Kawakubo (LSU),K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), I. Takahashi (IPMU), Y. Asaoka, S. Ozawa, (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), W. Ishizaki (ICRR), M. L. Cherry (LSU), S. Ricciarini (U of Florence), A. V. Penacchioni, P. S. Marrocchesi (U of Siena) and the CALET collaboration: The CALET Gamma-ray Burst Monitor (CGBM) was operating at the trigger time of S190408an (The LIGO Scientific Collaboration and Virgo Collaboration, GCN Circ. 24069). No CGBM on-board trigger occurred around the event time. Based on the LIGO-Virgo localization sky map, most of the part of the high probability area was in the field-of-view of CGBM. The summed LIGO probabilities inside the HXM and the SGM field of view are 91% and 95%. Based on the analysis of the light curve data with 0.125 sec time resolution from -60 sec to 60 sec from the trigger time, we found no significant excess around the trigger time in either the HXM (7-3000 keV) or the SGM (40 keV -28 MeV) data. The CALET Calorimeter (CAL) was operating in low energy trigger mode at the trigger time of S190408an. Using CAL data, we have searched for gamma-ray events in the 1-10 GeV band from -60 sec to +60 sec from the GW trigger time and found no candidates. The 90% upper limit of CAL is 2.3 x 10^-6 erg/cm2/s (1-10 GeV) when the summed LIGO-Virgo probabilities reaches at 80%. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24090 SUBJECT: LIGO/Virgo S190408an: GRAWITA optical observations of MASTER OT J231043.63+470956.4 DATE: 19/04/10 13:43:31 GMT FROM: Massimo Turatto at Obs.Astro.Padova, Italy F. Onori (INAF-IAPS Roma), M. Turatto (INAF-OAPd), S. Benetti (INAF-OAPd), L. Tomasella (INAF-OAPd), L. Nicastro (INAF-OAS), E. Palazzi (INAF-OAS), A. Melandri (INAF-OAB), S. Piranomonte (INAF-OAR), S. Yang (INAF-OAPd), P. D’Avanzo (INAF-OAB), M. Cecconi (INAF-TNG), A. Ghedina (INAF-TNG), H. Stoev (INAF-TNG), A. Brosio (Osservatorio Astronomico Lilio), S. Savaglio (UniCal) on behalf of GRAWITA report: We carried out follow-up observations of the optical transient MASTER OT J231043.63+470956.4, discovered by Lipunov et al. (GCN Circ. #24084) during observations of the skymap of the LIGO/Virgo event S190408an (LVC, GCN Circ. #24069). Optical imaging observations were obtained with the 0.5m telescope of the Osservatorio Astronomico Lilio, located in Savelli (Italy) starting on 2019-04-10 at 02:08:51 UT with the g-sdss, r-sdss, i-sdss filter. The OT is clearly detected with r~15.59+/- 0.02 mag (AB). We observed the transient with the 3.6m Italian TNG telescope (Canary Islands, Spain), equipped with the DOLORES camera in spectroscopic mode starting on 2019-04-10 at 04-57-48 UT. A total of 3 optical spectra, each one lasting 180 s, were obtained using the grism LR-B (wavelength range ~ 400-800 nm, resolution 1.05 nm). The spectrum shows a weak Halpha emission and other Balmer lines in absorption at z=0, superposed on a bright continuum. These results are consistent with MASTER OT J231043.63+470956.4 being a Galactic transient (likely a CV). The transient is therefore unrelated with the LIGO/Virgo GW event S190804an (as already proposed by Lipunov et al. GCN Circ 24084). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24091 SUBJECT: LIGO/Virgo S190408an: MAXI/GSC Observations DATE: 19/04/10 14:06:38 GMT FROM: Hitoshi Negoro at Nihon U H. Negoro (Nihon U.), M. Serino, S. Sugita (AGU), M. Sugizaki, N. Kawai (Tokyo Tech), M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi (Nihon U.), S. Nakahira, T. Mihara, M. Matsuoka (RIKEN), T. Sakamoto, A. Yoshida (AGU), Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, T. Sato (Chuo U.), M. Shidatsu (Ehime U.), Y. Tachibana, K. Morita, 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, T. Morita, S. Yamada, S. Ogawa (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: At the LVC trigger time of S190408an, 18:18:02.29 UT on 2019 April 8 (LIGO/Virgo Collaboration, GCN Circ. 24069), MAXI/GSC was scanning a part of the 50% credible region, centered around (R.A., Dec) = (333 deg, 20 deg), but no flaring event was detected. For one orbital period about 92 min, MAXI covered about 82% of the 90% credible region. Any enhancement was recognized in the region, and a typical (averaged) 1-sigma upper limit was 28 mCrab at 2-20 keV. MAXI observed the whole 90% credible region in 6 hours, and we put upper limits of typically about 15 mCrab, and partially about 50 mCrab for the regions observed with the degraded GSC_3 camera. Finally we note that MAXI detected GRB 190408A prior to the LVC trigger by 12 min (Sugita et al. GCN Circ. 24072). The burst was relatively short (~ 10 sec) and soft, but the GRB location, (R.A., Dec) = (47.3 deg, 1.8 deg), is far from the GW localization region. Thus, an association between these events is likely low. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24092 SUBJECT: LIGO/Virgo S190408an: MASTER OT J231043.63+470956.4 BOOTES-4 and 10.4m GTC follow-up observations DATE: 19/04/10 14:16:47 GMT FROM: Alberto J. Castro-Tirado at IAA-CSIC A. F. Valeev, I. V. Sokolov and V. V. Sokolov (SAO-RAS), Y.-D. Hu, X.-Y. Li and A. J. Castro-Tirado (IAA-CSIC), I. Carrasco (UMA), R. Sanchez-Ramirez (INAF-IAPS), M. D. Caballero-Garcia (ASU-CAS) and P. Pessev (GRANTECAN, IAC, ULL), on behalf  of a larger collaboration, report: Following the new optical transient MASTER OT J231043.63+470956.4 (Lipunov et al. GCNC 24084) within the LIGO/Virgo error box (GCNC 24069), we have followed it up with the BOOTES-4/MET 0.6m robotic telescope in Lijiang (China) confirming its brightness (r = 15.3 mag on Apr 9, 21UT). Furthermore, we have taken a 300s spectrum with the 10.4m GTC (+OSIRIS) telescope in La Palma (Spain). The spectrum shows a blue continuum with Balmer lines in absorption with the exception of H-alpha in emission, all at zero redshift. This is consistent with a dwarf nova spectrum undergoing a superoutburst, taking into account the > 7 mag amplitude in optical brightness with respect to the quiescence phase. Therefore this OT is unrelated to S190408an, in agreement with the Onori et al. findings (GCNC 24090). We acknowledge the excellent support from the GTC staff. [GCN OPS NOTE(11apr19): Per author's request, the following typos were corrected: " Peseev" --> "Pessev"; "taking accound the" --> "taking into account".] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24096 SUBJECT: LIGO/Virgo S190408an: Pan-STARRS observations and transients in the skymap DATE: 19/04/11 00:30:40 GMT FROM: Ken Smith at Queen's University Belfast K. W. Smith, D. R. Young, M. Huber, K. C. Chambers, S. J. Smartt, O. McBrien, J. Gillanders. S. Srivastav, D. O'Neil, P. Clark, S. Sim (QUB), E. Magnier, A. Schultz, (IfA, Univ. Hawaii), L. Denneau, H. Flewelling, A. Heinze, J. Tonry, H. Weiland, A. Rest (STScI), B. Stalder (LSST), C. Stubbs (Harvard) We report observations of the BAYESTAR skymap of the BBH event S190804an (The LIGO Scientific Collaboration and the Virgo Collaboration, GCN 24069) with the Pan-STARRS1 telescope (Chambers et al. 2016, arXiv:1612.05560C). Images were taken in the PS1 w,z and y-bands (Tonry et al. 2012, ApJ 750, 99) in the standard NEO search sequence. At each pointing position a sequence of quads (4 x 45 sec) was taken. This observing sequence ensures exactly the same pointing position for each of the quads. We estimate that the active pixel area covered 72 square degrees and a summed probability of 11% of the BAYESTAR skymap. We began taking data at 2019-04-09 14:30 (UTC) 20hrs after the GW trigger. The images were processed with the IPP (Magnier et al. 2016, arXiv:1612.05240) and difference images were produced using the Pan-STARRS1 Science Consortium 3Pi images as reference frames. Transient candidates were run through our standard filtering procedures, combined with a machine learning algorithm (Wright et al. 2015, MNRAS, 449, 451) were applied and all candidates were spatially cross-matched with known minor planets, and major star, galaxy, AGN and multi-wavelength catalogues (as described in Smartt et al. 2016, MNRAS, 462 4094). We find 3 new transients. None of which appear to possess any peculiar feature that indicates any link to S190804an. bPC denotes the percentage probability contour within which the transient is found according to the bayestar.fits map. Object RA DEC Disc Mag filt MJD z bPC Notes ------------------------------------------------------------------------- PS19pn 339.15090 +33.16465 20.40 0.21 w 58582.6099 - 60% (1) PS19pm 337.33525 +25.26419 19.87 0.14 w 58582.6061 ~0.195 80% (2) PS19pl 335.17707 +31.17752 19.44 0.12 w 58582.6086 ~0.083 90% (3) (1) Orphan, no host object (2) Nuclear Transient coincident with SDSS J222920.46+251551.0; an r=18.31 mag galaxy found in the SDSS DR12 PhotoObjAll Table catalogue. It's located 0.2" from the galaxy core. A host photoZ=0.195 (±0.031) implies absolute mag of M = -20. There is some variability history at similar flux levels in Pan-STARRS data. (3) Probably associated with SDSS J222042.60+311038.3; an r=17.26 mag galaxy found in the SDSS DR12 PhotoObjAll Table catalogue. It's located 0.69" N, 1.35" W from the galaxy centre. A host photoZ=0.083 (±0.020) implies an absolute mag of M = -18.5 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24097 SUBJECT: LIGO/Virgo S190408an: GROND Observations of MASTER OT J154209.55-431742.2 DATE: 19/04/11 12:33:12 GMT FROM: Ting-Wan Chen at MPE T.-W. Chen (MPE, Humboldt Fellow), T. Schweyer (MPE), A. Rossi (INAF-OAS), K. E. Heintz (Univ. of Iceland), M. Gromadzki (Univ. of Warsaw), J. Bolmer (MPE) and P. Schady (Bath) We observed again the field of the MASTER OT J154209.55-431742.2 (GCN#24084, Lipunov et al.) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile). Observations started at 07:23 UT on 10 of April 2019, about 1.25 days after the MASTER OT discovery, and were performed under seeing conditions 1".0, and at an average airmass of 1.0. We detect the candidate and based on 8.3 min of total exposure time. We derive the following preliminary magnitudes (all in the AB system): g = 16.70 +/- 0.01 mag, r = 16.82 +/- 0.01 mag, i = 17.05 +/- 0.01 mag, z = 17.14 +/- 0.01 mag, J = 17.11 +/- 0.01 mag, H = 17.71 +/- 0.03 mag, and K = 17.95 +/- 0.07 mag. Given magnitudes are calibrated against GROND zeropoint as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.24 mag in the direction of the counterpart (Schlafly & Finkbeiner 2011). We searched for previous observations. No source is detected in archival DSS and DSS2 red images and IR images. However, we have found that the source was detected in March 2015 by the SkyMapper Southern Sky Survey with vgriz: 17.798 +/- 0.034, 17.588 +/- 0.011, 17.593 +/- 0.030, 17.541 +/- 0.032, 17.703 +/- 0.040 (PSF magnitudes, AB) not corrected for galactic extinction (http://skymapper.anu.edu.au/object-viewer/dr1/179882566/). We have also searched for previous observations in the VISTA Hemisphere Survey. In images obtained on April 2010 we found a very faint source with J = 20.9 +/- 0.5 mags (Vega), while in K-band we can only provide an upperlimit K>19.0 mag, calibrated against 2MASS field stars. The SED obtained from archival images points to a very blue star. The late photometry from GROND, shows a ~5 magnitude brightening in the J band. These findings support the idea that this object is likely a bright infrared nova based on the SED and not related with the GW. We also noticed that the source is not detected in GAIA dr1 and 2 down to g=19.5, implying that skymapper and GROND observations were obtained during an outburst. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24106 SUBJECT: LIGO/Virgo S190408an: Gaia Photometric Alerts transient candidate DATE: 19/04/12 14:24:33 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 S190408an (Singer et al. GCN 24069): --------------------------------------------------------------------------- Name TNSid Date [TCB] RaDeg DecDeg AlertMag URL --------------------------------------------------------------------------- Gaia19bhc AT2019ddt 2019-04-07 15:17:19 347.68061 47.16521 15.26 http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19bhc/ --------------------------------------------------------------------------- The transient was discovered by the MASTER survey on 2019-04-09.00417 UT (MASTER OT J231043.63+470956.4; Lipunov et al. GCN 24084). However, the transient was observed by Gaia one day before the LIGO/Virgo trigger thereby re-enforcing the conclusion from Onori et al. (GCN 24090) and Valeev et al. (GCN 24092) that it is unrelated to the GW event S190408an. 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: 24107 SUBJECT: LIGO/Virgo S190408an: ATLAS observations of the S190412m skymap DATE: 19/04/12 14:57:03 GMT FROM: Stephen Smartt at Queen's U/Belfast H. Weiland (IfA, Univ. of Hawaii), K. W. Smith, D. R. Young, (Queen's University Belfast), L. Denneau, H. Flewelling, A. Heinze, J. Tonry (IfA), S. Smartt, O. McBrien, J. Gillanders,nS. Srivastav, D. O'Neil, P. Clark, S. Sim (QUB), A. Rest (STScI), B. Stalder (LSST), C. Stubbs (Harvard), E. Magnier, A. Schultz, , M. Huber, K. C. Chambers (IfA) We report observations of the BAYESTAR skymap of the BBH event S190412m (The LIGO Scientific Collaboration and the Virgo Collaboration, GCN 24098) with the ATLAS telescope system (Tonry et al. 2018, PASP, 13, 164505). ATLAS is a twin 0.5m telescope system on Haleakala and Mauna Loa employing two filters cyan and orange. While carrying out the primary mission for Near Earth Objects, we can adjust the schedule rapidly to point at LVC gravitational wave skymaps. Sequences of 30 sec images were taken in the ATLAS o/c bands, and at each pointing position a sequence of quads (4 x 30 sec) was taken. The images were processed with the ATLAS pipeline and reference images subtracted from each one. Transient candidates were run through our standard filtering procedures, combined with machine learning algorithms (e.g. Wright et al. 2015, MNRAS, 449, 451). Candidates were spatially cross-matched with known minor planets, and star, galaxy, AGN and multi-wavelength catalogues (as described in Smartt et al. 2016, MNRAS, 462 4094, Stalder et al. 2017, ApJ, 850, 149). We covered 137 square degrees of the bayestar map 90% credible region and covered a sky region totalling 91% of the event’s full localisation likelihood. Data acquisition began at 58585.300570 or 2019-04-12 07:12:49 (UTC), 41 mins after the PRELIMINARY notice and 102 mins after the GW merger event. All data acquisition finished approximately 4hrs later. We found no new transients to magnitudes of o < 19.1 (the median of the 5 sigma limits of the individual 30 sec images) between ~40 to ~240 minutes after the BBH merger. This work has made use of data from the Asteroid Terrestrial-impact Last Alert System (ATLAS) project. ATLAS is primarily funded to search for near earth asteroids through NASA grants NN12AR55G, 80NSSC18K0284, and 80NSSC18K1575; byproducts of the NEO search include images and catalogs from the survey area. The ATLAS science products have been made possible through the contributions of the University of Hawaii Institute for Astronomy, the Queen's University Belfast, and the Space Telescope Science Institute. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24124 SUBJECT: LIGO/Virgo S190408an: Gaia Photometric Alerts transient candidate DATE: 19/04/15 21:41:42 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 S190408an (Singer et al. GCN 24069): --------------------------------------------------------------------------- Name TNSid Date [TCB] RaDeg DecDeg AlertMag URL --------------------------------------------------------------------------- Gaia19bij AT2019dmx 2019-04-10 13:34:31 347.81400 44.91844 18.94 http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19bij/ --------------------------------------------------------------------------- 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: 24134 SUBJECT: LIGO/Virgo S190408an: Gaia Photometric Alerts transient candidates DATE: 19/04/19 21:56:13 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 transient candidates within the probability skymap of S190408an (Singer et al. GCN 24069): --------------------------------------------------------------------------- Name TNSid Date [TCB] RaDeg DecDeg AlertMag URL --------------------------------------------------------------------------- Gaia19bkj AT2019dpg 2019-04-16T20:07:27 335.67749 19.60641 18.95 http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19bkj/ Gaia19bkd AT2019dma 2019-04-16T13:48:35 343.70771 36.54362 17.34 http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19bkd/ Gaia19bju AT2019dmc 2019-04-12T09:34:12 338.36352 36.07027 16.19 http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19bju/ Gaia19bji AT2019doo 2019-04-12T15:26:12 345.74049 41.71289 18.91 http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19bji/ --------------------------------------------------------------------------- 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: 24139 SUBJECT: LIGO/Virgo S190408an: INTEGRAL follow-up observations DATE: 19/04/21 23:30:53 GMT FROM: Alexander Lutovinov at Space Research Inst.,IKI A. Lutovinov, S. Molkov (IKI, Russia) V. Savchenko, C. Ferrigno, E. Bozzo, T. Courvoisier (ISDC/UniGE, Switzerland) E. Kuulkers (ESTEC/ESA, The Netherlands) C. Sanchez (ESAC/ESA, Spain) S. Mereghetti (INAF IASF-Milano, Italy) D. Götz, Ph. Laurent, S. Schanne, B. Cordier (CEA, France) S.Antier, A. Coleiro, A. Goldwurm (APC, France) J. Rodi, A. Bazzano, L. Natalucci, F. Panessa, F. Onori, P. Ubertini (IAPS/INAF, Italy) J. Chenevez, S. Brandt (DTU, Denmark) R. Diehl, A. von Kienlin (MPE, Germany) A. Domingo, J. M. Mas-Hesse (CAB/CSIC-INTA, Spain) L. Hanlon, A. Martin-Carrillo, M.Doyle (UCD, Ireland) R. Sunyaev (IKI, Russia) J.-P. Roques, E. Jourdain, P. von Ballmoos (IRAP, France) report: The INTEGRAL observatory performed follow-up observations of the LIGO/Virgo compact binary merger candidate S190408an (GCN #24069) in the form of the fast TOO operational test. The observations were carried out from 2019-04-10 11:13:07 to 2019-04-10 17:10:47 in the staring and hexagonal dithering modes with a total observing time of approximately 18 ks. They were centred on the coordinates RA=350.2, Dec=-56.0 and covered ~42% of the LIGO/Virgo localization probability with the highest sensitivity. We do not detect any new sources in the complete IBIS/ISGRI (25-60 keV)  mosaicked image with the best sensitivity of 16.5 mCrab (1.6e-10 erg/cm2/s, 3-sigma upper level) in this energy range. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 24154 SUBJECT: LIGO/Virgo S190408an: Liverpool Telescope follow-up imaging observations DATE: 19/04/23 12:17:13 GMT FROM: Peter Jonker at SRON/RU P.G. Jonker (SRON/RU), M. Fraser (UCD), Manuel Torres (IAC), Pablo Rodriguez-Gil (University of La Laguna), Kate Maguire (TCD), Z. Kostrzewa-Rutkowska (SRON/RU), report, on behalf of the International Time Proposal team, on Liverpool Telescope 3x300 sec r'-band imaging observations obtained on 2019-04-21T05:47:58 of the transient candidate(s) Gaia19bij found by the Gaia Alerts team (Kostrzewa-Rutkowska et al. GCN#24124) in the sky localisation region of GW190408 / S190408an (Singer et al. GCN 24069): Gaia19bij was found at r'~19, approximately 1.5" off-nuclear from a faint host galaxy. Acknowledgements: PGJ and ZKR acknowledge support from the European Research Council under ERC Consolidator Grant agreement no 647208.