//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26755 SUBJECT: LIGO/Virgo S200115j: Global MASTER-Net observations report DATE: 20/01/15 04:36:36 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, D. Cheryasov (Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University) MASTER-IAC robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Spain (IAC Teide Observatory) started inspect of the LIGO/Virgo S200115j errorbox 438 sec after trigger time at 2020-01-15 04:30:27 UT, with upper limit up to 14.6 mag. The observations began at zenith distance = 44 deg. The sun altitude is -44.7 deg. The galactic latitude b = -31 deg., longitude l = 347 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/ligo_1.php?id=11234 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 484 | 2020-01-15 04:30:27 | MASTER-IAC | (09h 55m 13.34s , +71d 23m 02.5s) | P| | 90 | 14.6 | 484 | 2020-01-15 04:30:27 | MASTER-IAC | (09h 53m 18.93s , +71d 25m 54.8s) | P- | 90 | 14.5 | The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26756 SUBJECT: LIGO/Virgo trigger S200115j: Possible host galaxies DATE: 20/01/15 05:08:14 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester) reports, The bayestar.fits.gz,0 GW skymap has been convolved with the 2MPZ galaxy catalogue (Bilicki et al., ApJS, 210, 9), using the method described in Evans et al (2016, MNRAS, 462, 1591*), to identify a ranked list of potential host galaxies of the LVC trigger S200115j. This galaxy ranking method accounts for the (line-of-sight dependent) completeness of 2MPZ, GW probability, and the overlap between P(D) functions for the GW event and the individual galaxies. In total 9105 galaxies with P>10^-5 have been identified. The most probable 20 are listed below, a full list and more details are available at: https://www.swift.ac.uk/LVC/S200115j/galaxies | Galaxy name | P_host | RA | Dec | K_abs | GalDist | -------------------------------------------------------------------------------------------------- | 2MPZ J02594896+0334138 | 3.14e-03 | 02h 59m 48.96s | +03d 34' 13.8" | 10.7 | 299.5 +/- 7.4 | | 2MPZ J03024884+0351494 | 1.84e-03 | 03h 02m 48.84s | +03d 51' 49.5" | 11.1 | 317.7 +/- 7.4 | | 2MPZ J02595945+0322468 | 1.70e-03 | 02h 59m 59.45s | +03d 22' 46.8" | 11.3 | 300.5 +/- 7.4 | | 2MPZ J19502998-5030374 | 1.52e-03 | 19h 50m 30.00s | -50d 30' 37.4" | 11.7 | 416.8 +/- 7.4 | | 2MPZ J02543798+0056218 | 1.50e-03 | 02h 54m 37.99s | +00d 56' 21.8" | 11.6 | 300.4 +/- 7.4 | | 2MPZ J02541454+0101446 | 1.34e-03 | 02h 54m 14.54s | +01d 01' 44.6" | 11.8 | 303.9 +/- 7.4 | | 2MPZ J19492167-5045558 | 1.17e-03 | 19h 49m 21.60s | -50d 45' 55.8" | 12.0 | 418.5 +/- 7.4 | | 2MPZ J02414023-0254238 | 1.05e-03 | 02h 41m 40.25s | -02d 54' 23.9" | 11.7 | 303.7 +/- 7.4 | | 2MPZ J02511474-0019452 | 9.91e-04 | 02h 51m 14.76s | -00d 19' 45.3" | 12.1 | 301.4 +/- 7.4 | | 2MPZ J02411531-0547234 | 9.89e-04 | 02h 41m 15.31s | -05d 47' 23.5" | 11.4 | 320.3 +/- 7.4 | | 2MPZ J02523222-0002526 | 9.79e-04 | 02h 52m 32.23s | -00d 02' 52.6" | 12.0 | 324.3 +/- 7.4 | | 2MPZ J19512421-5024363 | 8.64e-04 | 19h 51m 24.24s | -50d 24' 36.4" | 11.5 | 297.1 +/- 7.4 | | 2MPZ J19551231-5110295 | 8.62e-04 | 19h 55m 12.24s | -51d 10' 29.6" | 12.4 | 426.3 +/- 7.4 | | 2MPZ J19530336-5202132 | 8.55e-04 | 19h 53m 3.36s | -52d 02' 13.2" | 11.7 | 309.7 +/- 63.2 | | 2MPZ J02555367+0051381 | 8.38e-04 | 02h 55m 53.69s | +00d 51' 38.1" | 12.1 | 300.6 +/- 7.4 | | 2MPZ J02530482+0555431 | 8.17e-04 | 02h 53m 4.82s | +05d 55' 43.1" | 11.5 | 322.7 +/- 7.4 | | 2MPZ J19521735-5159465 | 7.85e-04 | 19h 52m 17.28s | -51d 59' 46.7" | 11.6 | 497.2 +/- 7.4 | | 2MPZ J02592648+0358163 | 7.79e-04 | 02h 59m 26.47s | +03d 58' 16.3" | 12.1 | 319.7 +/- 64.0 | | 2MPZ J19484858-5148290 | 7.64e-04 | 19h 48m 48.48s | -51d 48' 29.2" | 12.2 | 473.9 +/- 73.8 | | 2MPZ J19490816-5002317 | 7.45e-04 | 19h 49m 8.16s | -50d 02' 31.9" | 12.2 | 417.0 +/- 7.4 | -------------------------------------------------------------------------------------------------- (* See also the erratum: MNRAS, 484, 2362; or arXiv 1606.05001 for the full manuscript with erratum applied). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26757 SUBJECT: LIGO/Virgo S200115j: Upper limits from IceCube neutrino searches DATE: 20/01/15 05:28:30 GMT FROM: Raamis Hussain at IceCube IceCube Collaboration (http://icecube.wisc.edu/) reports: Searches [1,2] for track-like muon neutrino events detected by IceCube consistent with the sky localization of gravitational-wave candidate S200115j in a time range of 1000 seconds [3] centered on the alert event time (2020-01-15 04:14:49.753 UTC to 2020-01-15 04:31:29.753 UTC) have been performed. During this time period IceCube was collecting good quality data. No significant track-like events are found in spatial coincidence of S200115j calculated from the map circulated in the 2-Preliminary notice. IceCube's sensitivity assuming an E^-2 spectrum (E^2 dN/dE) to neutrino point sources within the locations spanned by the 90% spatial containment of S200115j ranges from 0.029 to 0.754 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 [1] Bartos et al. arXiv:1810.11467 (2018) and Countryman et al.arXiv:1901.05486 (2019) [2] PoS(ICRC2019)918 and Braun et al., Astroparticle Physics 29, 299 (2008) [3] Baret et al., Astroparticle Physics 35, 1 (2011) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26758 SUBJECT: LIGO/Virgo S200115j: No counterpart candidates in HAWC observations DATE: 20/01/15 05:54:58 GMT FROM: Antonio Galvan at Inst.de Astronomia,UNAM The HAWC Collaboration (https://www.hawc-observatory.org) reports: The HAWC Collaboration performed a follow-up of the gravitational wave trigger S200115j. At the time of the trigger the HAWC local zenith was oriented towards (RA, Dec) = (82.3 deg, 19.0 deg). 46% 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 22.5 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 2.8e-06 erg/cm^2 to 1.1e-04 erg/cm^2 (1.5e-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: 26759 SUBJECT: LIGO/Virgo S200115j: Identification of a GW compact binary merger candidate DATE: 20/01/15 06:08:31 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 S200115j during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2020-01-15 04:23:09.742 UTC (GPS time: 1263097407.742). The candidate was found by the GstLAL [1], PyCBC Live [2], MBTAOnline [3], and SPIIR [4] analysis pipelines. S200115j is an event of interest because its false alarm rate, as estimated by the online analysis, is 2.1e-11 Hz, or about one in 1e3 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S200115j The classification of the GW signal, in order of descending probability, is MassGap (>99%), Terrestrial (<1%), BNS (<1%), NSBH (<1%), or BBH (<1%). Assuming the candidate is astrophysical in origin, the probability that the lighter compact object has a mass < 3 solar masses (HasNS) is >99%. Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is 9%. Three sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.fits.gz,0, an initial localization generated by BAYESTAR [5], distributed via GCN notice about 6 minutes after the candidate event time. * bayestar.fits.gz,1, an initial localization generated by BAYESTAR [5], distributed via GCN notice about 12 minutes after the candidate event time. * bayestar.fits.gz,2, an initial localization generated by BAYESTAR [5], distributed via GCN notice about an hour after the candidate event time. The preferred sky map at this time is bayestar.fits.gz,2. For the bayestar.fits.gz,2 sky map, the 90% credible region is 908 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 331 +/- 97 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] Nitz et al. PRD 98, 024050 (2018) [3] Adams et al. CQG 33, 175012 (2016) [4] Qi Chu, PhD Thesis, The University of Western Australia (2017) [5] Singer & Price PRD 93, 024013 (2016) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26760 SUBJECT: LIGO/Virgo S200115j: Coverage and upper limits from MAXI/GSC observations DATE: 20/01/15 06:22:00 GMT FROM: Satoshi Sugita at Aoyama Gakuin U. N. Kawai (Tokyo Tech), H. Negoro (Nihon U.), S. Sugita, M. Serino (AGU), M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi, R. Takagi (Nihon U.), T. Mihara, C. Guo, Y. Zhou, 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. Nakahira, Y. Sugawara, S. Ueno, H. Tomida, M. Ishikawa, 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, K. Kurogi, K. Miike (Miyazaki U.), T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU), M. Sugizaki (NAOC) report on behalf of the MAXI team: We examined MAXI/GSC all-sky X-ray images (2-20 keV) after the LVC trigger S200115j at 2020-01-15 04:23:09.742 UTC (GCN 26759). At the trigger time of S200115j, the high-voltage of MAXI/GSC was off, and it was turned on at T0+922 sec (+15.4 min). The first one-orbit (92 min) scan observation with GSC after the event covered 99% of the 90% credible region of the bayestar skymap from 04:38:32 to 05:50:56 UTC (T0+923 to T0+5267 sec). No significant new source was found in the region in the one-orbit scan observation. A typical 1-sigma averaged upper limit obtained in one scan observation is 20 mCrab at 2-20 keV. If you require information about X-ray flux by MAXI/GSC at specific coordinates, please contact the submitter of this circular by email. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26762 SUBJECT: LIGO/Virgo S200115j : no neutrino counterpart candidate in ANTARES search DATE: 20/01/15 07:56:04 GMT FROM: Thierry Pradier at ANTARES/IPHC/U of Strasbourg M. Ageron (CPPM/CNRS), B. Baret (APC/CNRS), A. Coleiro (APC/Universite de Paris), M. Colomer (APC/Universite de Paris), D. Dornic (CPPM/CNRS), A. Kouchner (APC/Universite de Paris), 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 S200115j event using the 90% contour of the Initial GW_SKYMAP probability map provided by the GW interferometers (GCN#26759 ). The ANTARES visibility at the time of the alert, together with the 50% and 90% contours of the probability map are shown at http://antares.in2p3.fr/GW/S200115j_Initial.png . Considering the location probability provided by the LIGO/Virgo collaborations, there is a 76.0% 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 2020-01-15 04:23:09 and in the 90% contour of the S200115j event. The expected number of atmospheric background events in the region visible by ANTARES is 4.25e-04 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 3.06e-03 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: 26763 SUBJECT: LIGO/Virgo S200115j: Revised list of possible host galaxies with the new skymap DATE: 20/01/15 08:24:43 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester) reports, The bayestar.fits.gz,2 GW skymap circulated with the "Initial" skymap notice differs somewhat from the earlier skymap (see GCN Circ. 26759 for a list of the skymaps available). Thus the earlier list of possible hosts galaxies (GCN Circ. 26756) is no longer appropriate and has been revised. In total 9311 galaxies with P>10^-5 have been identified. The most probable 20 are listed below, a full list and more details are available at: https://www.swift.ac.uk/LVC/83/galaxies This page will automatically update after any new skymap is released, and the galaxy list for any skymap can be selected. | Galaxy name | P_host | RA | Dec | K_abs | GalDist | -------------------------------------------------------------------------------------------------- | 2MPZ J02471224+0539536 | 2.36e-03 | 02h 47m 12.24s | +05d 39' 53.6" | 10.8 | 305.4 ± 7.4 | | 2MPZ J02530482+0555431 | 1.74e-03 | 02h 53m 4.82s | +05d 55' 43.1" | 11.5 | 322.7 ± 7.4 | | 2MPZ J02454537+0548217 | 1.55e-03 | 02h 45m 45.38s | +05d 48' 21.7" | 11.0 | 305.4 ± 7.4 | | 2MPZ J02524584+0639206 | 1.42e-03 | 02h 52m 45.84s | +06d 39' 20.7" | 11.5 | 281.3 ± 7.4 | | 2MPZ J02465369+0535216 | 1.37e-03 | 02h 46m 53.69s | +05d 35' 21.7" | 11.4 | 309.6 ± 7.4 | | 2MPZ J02594896+0334138 | 1.07e-03 | 02h 59m 48.96s | +03d 34' 13.8" | 10.7 | 299.5 ± 7.4 | | 2MPZ J02575308+1301508 | 9.47e-04 | 02h 57m 53.09s | +13d 01' 50.9" | 10.6 | 321.8 ± 7.4 | | 2MPZ J19502998-5030374 | 9.32e-04 | 19h 50m 30.00s | -50d 30' 37.4" | 11.7 | 416.8 ± 7.4 | | 2MPZ J02585781+1334583 | 8.84e-04 | 02h 58m 57.82s | +13d 34' 58.4" | 10.7 | 336.1 ± 7.4 | | 2MPZ J02415655+0138341 | 8.65e-04 | 02h 41m 56.54s | +01d 38' 34.1" | 11.7 | 339.3 ± 65.4 | | 2MPZ J02343922-0237357 | 8.55e-04 | 02h 34m 39.22s | -02d 37' 35.7" | 11.6 | 312.1 ± 7.4 | | 2MPZ J02535594+0601445 | 8.34e-04 | 02h 53m 55.94s | +06d 01' 44.6" | 12.0 | 342.0 ± 65.6 | | 2MPZ J02492989+0331401 | 8.32e-04 | 02h 49m 29.90s | +03d 31' 40.1" | 12.0 | 341.4 ± 65.6 | | 2MPZ J02434093+0200347 | 8.26e-04 | 02h 43m 40.94s | +02d 00' 34.7" | 11.8 | 353.6 ± 66.5 | | 2MPZ J02535064+0839375 | 7.48e-04 | 02h 53m 50.64s | +08d 39' 37.6" | 10.9 | 227.7 ± 7.4 | | 2MPZ J02414023-0254238 | 7.24e-04 | 02h 41m 40.25s | -02d 54' 23.9" | 11.7 | 303.7 ± 7.4 | | 2MPZ J02524248+0642066 | 6.88e-04 | 02h 52m 42.48s | +06d 42' 06.7" | 12.2 | 375.7 ± 68.0 | | 2MPZ J02450740+0117093 | 6.87e-04 | 02h 45m 7.42s | +01d 17' 09.3" | 12.0 | 293.7 ± 61.9 | | 2MPZ J02551143+0912138 | 6.52e-04 | 02h 55m 11.42s | +09d 12' 13.9" | 12.0 | 372.4 ± 67.8 | | 2MPZ J02265897-0435269 | 6.48e-04 | 02h 26m 58.97s | -04d 35' 27.0" | 11.1 | 314.7 ± 7.4 | -------------------------------------------------------------------------------------------------- //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26765 SUBJECT: LIGO/Virgo S200115j: upper limits from AGILE/MCAL observations DATE: 20/01/15 10:03:19 GMT FROM: Alessandro Ursi at INAF/IAPS A. Ursi (INAF/IAPS), F. Verrecchia, C. Pittori (SSDC, and INAF/OAR), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), M. Cardillo, C. Casentini, G. Piano (INAF/IAPS), F. Lucarelli (SSDC, and INAF/OAR), A. Bulgarelli, V. Fioretti, 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 S200115j at T0 = 2020-01-15 04:23:09.742 (UT), a preliminary analysis of the AGILE minicalorimeter (MCAL) triggered data found no event candidates within a time interval covering -/+ 15 sec from the LIGO/Virgo T0. At the T0, about 50% of the S200115j 90% c.l. localization region was accessible to the AGILE MCAL. Three-sigma upper limits (ULs) of the fluence are obtained for a 1 s integration time at different celestial positions within the accessible S200115j localization region, from a minimum of 1.4E-06 erg cm^-2 to a maximum of 7.6E-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: 26766 SUBJECT: LIGO/Virgo S200115j: INTEGRAL was inactive at the time of the event DATE: 20/01/15 10:21:59 GMT FROM: Carlo Ferrigno at IAAT/ISDC C. Ferrigno, V. Savchenko (ISDC/UniGE, Switzerland) S. Mereghetti (INAF IASF-Milano, Italy) J. Rodi (IAPS-Roma, Italy) A. Coleiro (APC, France) on behalf of the INTEGRAL multi-messenger collaboration: https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration The INTEGRAL spacecraft has a highly elliptical orbit and the instruments are not acquiring science data during perigee passage, every 2.6 days to prevent radiation-induced damages. Unfortunately, at the time of the S200115j (2020-01-15 04:23:09, GCN #26759) the spacecraft was preparing to the start the observations after the perigee passage between the orbits number 2182 and 2183 and no scientific instrument data are available between 2020-01-14 23:52:28 and 2020-01-15 09:24:40. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26767 SUBJECT: LIGO/Virgo S200115j: Candidates from the Zwicky Transient Facility DATE: 20/01/15 10:37:04 GMT FROM: Varun Bhalerao at Indian Inst of Tech Shreya Anand (Caltech), Harsh Kumar (IITB), Simeon Reusch (DESY), Varun Bhalerao (IITB), Leo Singer (NASA-GSFC), Michael Coughlin (UMinn), Igor Andreoni (Caltech), Matthew Graham (Caltech), Brad Cenko (UMD), David Kaplan (UWM), Mansi Kasliwal (Caltech) 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 S200115j, in the initial bayestar.fits.gz,2 skymap (LVC, GCN #26759) with the Palomar 48-inch telescope equipped with the 47 square degree Zwicky Transient Facility camera (ZTF, Bellm et al. 2019, Graham et al. 2019). The tiling was 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 beginning at 2020-01-15 06:28 UT. In our triggered 300s observations, we covered 36% of the enclosed probability to a median depth of 21.2 mag. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). Alert filtering and follow-up coordination was undertaken by the GROWTH Marshal system (Kasliwal et al. 2019). The ZTF alert stream was also queried using the Kowalski infrastructure (Duev et al., 2019) and with AMPEL (Nordin et al. 2019). Two of our candidates were located near galaxies detected in the PanSTARRs survey (Chambers et al. 2016). Phot-z estimates for these were based on ANNz2 (Sadeh et al. 2016). We identified the following candidates: ±-------------±---------±------------±-------------±-------±-----±---------±------±------+ | Name | IAU Name | RA | Dec | filter | mag | MJD | b_Gal | Notes | ±-------------±---------±------------±-------------±-------±-----±---------±------±------+ | ZTF20aafqpum | AT2020yo | 03:06:06.50 | +13:54:48.4 | g | 20.8 | 58863.27 | -37.5 | (a) | | ZTF20aafqulk | AT2020yp | 03:39:45.43 | +27:44:05.4 | g | 21.1 | 58863.29 | -21.9 | (b) | | ZTF20aafqvyc | AT2020yq | 03:47:58.21 | +38:26:31.8 | g | 20.9 | 58863.30 | -12.5 | | ±-------------±---------±------------±-------------±-------±-----±---------±------±------+ (a) Offset from possible host galaxy at redshift photz = 0.12 +/- 0.03 (b) Offset from possible host galaxy at redshift photz = 0.27 +/- 0.04 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; IITB, India; IIA, India; LJMU, UK; TTU, USA; SDSU, 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 coordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019). Alert database searches are done with using the Kowalski infrastructure (Duev et al., 2019) and with AMPEL (Nordin et al. 2019). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26769 SUBJECT: LIGO/Virgo S200115j: upper limits from AGILE/GRID observations DATE: 20/01/15 11:50:13 GMT FROM: Alessandro Ursi at INAF/IAPS A. Ursi (INAF/IAPS), C. Pittori, F. Verrecchia (SSDC, and INAF/OAR), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), M. Cardillo, C. Casentini, G. Piano (INAF/IAPS), F. Lucarelli (SSDC, and INAF/OAR), A. Bulgarelli, V. Fioretti, 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 S200115j at T0 = 2020-01-15 04:23:09.753 UTC a preliminary analysis of the AGILE exposure at T0 shows that the Gamma-Ray Imaging Detector (GRID) exposure covered less than 10% of the 90% c.l. localization region (LR) (46% of 90% c.l. localization region (LR) is occulted by Earth). We performed an analysis of the GRID data in the energy range 50 MeV - 10 GeV over time intervals before and after T0, where good exposure of the S200115j 90% c.l. LR was available. No candidate gamma-ray transient was detected. The following preliminary GRID values of 3-sigma upper limit (UL) are obtained: from 1.2e-07 to 3.6e-07 erg cm^-2 s^-1, with exposure of about 34% of the LR over the time interval ( T0 - 200s ; T0 - 100s ); from 3.9e-08 to 8.7e-06 erg cm^-2 s^-1, with exposure of about 32% of the LR over the time interval ( T0 + 200s ; T0 + 300s ). 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: 26774 SUBJECT: LIGO/Virgo S200115j: Upper limits from Fermi-GBM Observations DATE: 20/01/15 13:42:25 GMT FROM: Adam Goldstein at Fermi-GBM, USRA A. Goldstein (USRA) reports on behalf of the Fermi-GBM Team and the GBM-LIGO/Virgo group For S200115j and using the latest BAYESTAR skymap, Fermi-GBM was observing 84.4% 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 S200115j (GCN Circ. 26759). 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. Part of the LVC localization region is behind the Earth for Fermi, located at RA=137.7, Dec=23.9 with a radius of 67.2 degrees. We therefore set upper limits on impulsive gamma-ray emission for the LVC localization region visible to Fermi at merger time. Using the representative soft, normal, and hard GRB-like templates described in arXiv:1612.02395, we set the following 3 sigma flux upper limits over 10-1000 keV, weighted by GW localization probability (in units of 10^-7 erg/s/cm^2): Timescale Soft Normal Hard --------------------------------- 0.128 s: 4.6 8.3 17. 1.024 s: 1.5 2.8 6.1 8.192 s: 0.5 0.7 2.0 Assuming the median luminosity distance of 331 Mpc from the GW detection, we estimate the following intrinsic luminosity upper limits over the 1 keV-10 MeV energy range (in units of 10^48 erg/s): Timescale Soft Normal Hard --------------------------------- 0.128s: 9.2 15. 52. 1.024s: 3.0 5.2 19. 8.192s: 0.9 1.3 6.1 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26775 SUBJECT: LIGO/Virgo S200115j: No counterpart candidates in Fermi-LAT observations DATE: 20/01/15 14:21:36 GMT FROM: Milena Crnogorcevic at U. of Maryland,College Park M. Crnogorcevic (Univ. of Maryland & NASA/GSFC), L. Scotton (CNRS/IN2P3/LUPM), F. Longo (University and INFN, Trieste), E. Bissaldi (Politecnico & INFN Bari), M. Axelsson (KTH and Stockholm Univ.), N. Omodei (Stanford Univ.), and D. Kocevski (NASA/MSFC) report on behalf of the Fermi-LAT Collaboration: We have searched data collected by the Fermi Large Area Telescope (LAT) on January 15, 2020, for possible high-energy (E > 100 MeV) gamma-ray emission in spatial/temporal coincidence with the LIGO/Virgo trigger S200115j (GCN 26759). 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. Fermi-LAT had an instantaneous coverage of ~35% of the LIGO probability at the time of the trigger (T0 = 2020-01-15 04:23:09.742 UTC), and reached 100% cumulative coverage after ~6.6 ks. We performed a search for a transient counterpart within the observed region of the 90% contour of LIGO map in a fixed time window from T0 to T0 + 10 ks. 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, and no additional excesses were found. Energy flux upper bounds for the fixed time interval between 100 MeV and 1 GeV for this search vary between 1.4e-10 and 5.4e-09 [erg/cm^2/s]. The Fermi-LAT point of contact for this event is Milena Crnogorcevic (mcrnogor@astro.umd.edu ). 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: 26777 SUBJECT: LIGO/Virgo S200115j High Rank XRT sources are spurious DATE: 20/01/15 17:52:12 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester) reports Recently a significant number of GCN/COUNTERPART notices have been issued by the automated Swift/XRT analysis reporting sources with ranks 1 or 2, i.e. a strong candidate to be the counterpart. Unfortunately, none of these are real. Due to a period of unusually high XRT temperature, the background in some of our GW follow up is very elevated and inhomoegnious which has given rise to these spurious sources with apparently high fluxes. We apologise for any inconvenience. Users are reminded that all COUNTERPART notices are preliminary - they are produced from automated systems, pre human vetting; sources identified once manually confirmed will be made available through the website: https://www.swift.ac.uk/LVC/ and naturally, should we identify something which we consider of significant interest we shall of course confirm it in a circular at the earliest possible opportunity. We have disabled the distribution of the counterpart notices for S200115j due to these issues. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26779 SUBJECT: LIGO/Virgo S200115j: no counterpart candidates in the Swift/BAT observations DATE: 20/01/15 19:59:15 GMT FROM: Amy Lien at GSFC T. Sakamoto (AGU), S. D. Barthelmy (NASA/GSFC), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), A. P. Beardmore (U. Leicester), M. G. Bernardini (INAF-OAB), A. A. Breeveld (MSSL-UCL), 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 (ASI-ASDC), S. Emery (UCL-MSSL), P. A. Evans (U. Leicester), P. Giommi (ASI), C. Gronwall (PSU), D. Hartmann (Clemson U.), J. A. Kennea (PSU), N. Klingler (PSU), H. A. Krimm (NSF), N. P. M. Kuin (UCL-MSSL), F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), J. A. Nousek (PSU), S. R. Oates (U. of Birmingham), P. T. O'Brien (U. Leicester), J. P. Osborne (U. Leicester), C. Pagani (U. Leicester), K. L. Page (U.Leicester), M. J. Page (UCL-MSSL), M. Perri (ASDC), J. L. Racusin (NASA/GSFC), B. Sbarufatti (INAF-OAB/PSU), M. H. Siegel (PSU), G. Tagliaferri (INAF-OAB), A. Tohuvavohu (U. Toronto), 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 S200115j (LIGO/VIRGO Collaboration GCN Circ. 26759), where T0 is the LVC trigger time (2020-01-15T04:23:09.752 UTC). The center of the BAT field of view (FOV) at T0 is RA = 273.607 deg, DEC = 31.579 deg, and the roll angle is 148.273 deg. The BAT FOV (>10% partial coding) covers 5.58% of the integrated LVC localization probability, and 5.56% of the galaxy convolved probability (Evans et al. 2016). Note that the sensitivity in the BAT FOV changes with the partial coding fraction. Please see the BAT FOV figure in the summary page (link below) for the specific location of the LVC region relative to the BAT FOV. 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 ~ 8.91 x 10^-8 erg/s/cm^2. Assuming a luminosity of ~ 2 x 10^47 erg/s (similar to GW170817) and an average Epeak of ~ 400 keV for short GRBs (Bhat et al. 2016), this flux upper limit corresponds to a distance of ~ 76.12 Mpc. No event data are available at this time. BAT retains decreased, but significant, sensitivity to rate increases for gamma-ray events outside of its FOV. About 24.17% 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/S200115j/web/source_public.html //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26786 SUBJECT: LIGO/Virgo S200115j: no counterpart candidate in SVOM/GWAC observations DATE: 20/01/16 14:10:19 GMT FROM: Xuhui Han at NAOC/SVOM J. Y. Wei (NAOC), S. Guillot (CNRS/IRAP), J. Wang (GXU), S. Basa (CNRS/LAM), X. H. Han (NAOC) report on behalf of the SVOM Multi Messenger Astronomy and GWAC teams (http://www.svom.fr/en/svom-mma-and-gwac-team): We observed 17 (~2550 square deg) sky regions to cover the skymap of the advanced LIGO/Virgo trigger S200115j (GCN # 26759), with SVOM/GWAC, at Xinglong Observatory. SVOM/GWAC is equipped with two sets of wide angle cameras: - FFOV cameras (FOV~900 square degrees/camera, aperture = 3.5 cm), - JFOV cameras (FOV~150 square degrees/camera, aperture = 18 cm). SVOM/GWAC currently comprises 4 FFOV cameras and 16 JFOV cameras, working in the unfiltered band. The observations are operated in time-series mode, taking one exposure every 25 seconds (20s exposure + 5s readout). The observed and processed regions enclosed an estimated 67.1% of the probability of the advanced LIGO/Virgo skymap. Images were taken between ~7 hours and ~18 hours after the GW trigger time. The coordinates of the 17 sky regions observed and their observation times and covered probability are listed below: Id Ra Dec start (UTC) end (UTC) Proba. Cam. 1 05:50:26.3 51:50:22 2020-01-15 14:18:51 2020-01-15 14:46:00 0.003 JFOV 2 07:26:21.8 64:13:01 2020-01-15 14:18:51 2020-01-15 14:46:00 0.004 JFOV 3 09:44:22.8 68:18:18 2020-01-15 15:24:38 2020-01-15 15:53:38 0.010 JFOV 4 16:31:30.7 -3:13:56 2020-01-15 22:03:45 2020-01-15 22:05:47 0.020 JFOV 5 16:39:37.9 -14:35:58 2020-01-15 22:04:20 2020-01-15 22:14:51 0.040 JFOV 6 03:19:17.3 13:34:55 2020-01-15 12:43:57 2020-01-15 13:12:07 0.116 JFOV 7 03:19:57.0 01:29:44 2020-01-15 12:50:14 2020-01-15 13:12:07 0.058 JFOV 8 02:29:35.0 01:23:54 2020-01-15 12:55:06 2020-01-15 13:12:07 0.251 JFOV 9 02:42:06.7 -14:20:52 2020-01-15 12:53:27 2020-01-15 13:12:52 0.030 JFOV 10 03:29:53.5 -2:41:46 2020-01-15 12:57:06 2020-01-15 13:12:52 0.001 JFOV 11 04:20:51.2 47:50:40 2020-01-15 11:26:49 2020-01-15 11:56:36 0.071 JFOV 12 04:10:55.1 36:07:24 2020-01-15 11:26:49 2020-01-15 11:56:38 0.043 JFOV 13 02:59:22.0 35:09:36 2020-01-15 11:33:18 2020-01-15 14:15:11 0.005 JFOV 14 04:06:04.5 47:32:04 2020-01-15 11:34:00 2020-01-15 14:15:11 0.070 JFOV 15 04:00:51.0 35:21:07 2020-01-15 11:50:37 2020-01-15 14:15:11 0.050 JFOV 16 05:51:31.2 64:35:19 2020-01-15 13:16:53 2020-01-15 13:44:55 0.033 JFOV 17 05:32:23.9 52:57:41 2020-01-15 13:35:13 2020-01-15 13:44:55 0.018 JFOV The sky coverage map is available at: http://cmm.svom.cn/gwpub/O3/S200115j/S200115j.png (user:svomo3 pwd:gwo3). Weather conditions were clear during the observations. The sky regions are > 80 degrees from the moon (~0.72 of lunar phase). An average 3-sigma limiting magnitude of 16 mag in the R band was obtained in the single frames. No credible new source was detected by our online pipeline during follow-up observations. A more detailed image analysis including co-addition is ongoing with our offline pipeline to search for transient candidates. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26788 SUBJECT: LIGO/Virgo S200115j: No neutrino candidates at Pierre Auger Observatory DATE: 20/01/16 14:51:36 GMT FROM: Jaime Alvarez-Muniz at Pierre Auger Observatory J. Alvarez-Muniz, F. Pedreira, E. Zas (IGFAE & University of Santiago de Compostela, Spain), K. H. Kampert & M. Schimp (University of Wuppertal, Germany) on behalf of the Pierre Auger Collaboration. In response to: LIGO/Virgo GW trigger S200115j T0=2020-01-15 04:23:09 UTC We searched for Ultra-High-Energy (UHE) neutrinos with energies above ~ 1e17 eV in data collected with the Surface Detector (SD) of the Pierre Auger Observatory in a [-500,500] second interval about the LIGO-Virgo trigger S200115j as well as in a 24 hr time interval following the event. NO events survived the cuts applied to reject the background due to UHE Cosmic Rays i.e. NO neutrino candidates were detected. The field of view (fov) where the SD of Auger is sensitive to UHE neutrinos (corresponding to inclined directions with respect to the vertical relative to the ground) was PARTIALLY COINCIDENT (51.8%) at the time T0 of the merger alert, with the latest LIGO/Virgo 90% localization region (bayestar.fits.gz), achieving a MAXIMUM OVERLAP (56.1%) at approximately T0+23.33 hours. ------- The Pierre Auger Observatory is an UHE Cosmic Ray detector located in the Mendoza Province in Argentina. It consists of an array of Water Cherenkov detectors spread over a total surface of 3000 km^2 arranged in a triangular grid of 1.5 km side as well as Fluorescence telescopes and other systems (see 10.1016/j.nima.2015.06.058 for more information). For neutrino searches with Auger, please refer to: https://iopscience.iop.org/article/10.1088/1475-7516/2019/10/022 https://iopscience.iop.org/article/10.1088/1475-7516/2019/11/004 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26794 SUBJECT: LIGO/Virgo S200115j: No notable candidates in GOTO imaging DATE: 20/01/17 00:16:40 GMT FROM: Danny Steeghs at U.of Warwick/GOTO D.Steeghs (1); K.Ulaczyk (1); J.Lyman (1); R.Cutter (1); T.Killestein (1); M.Dyer (3); M.Kennedy (10); G.Ramsay (5); D.K.Galloway (2); V.Dhillon (3); P.O'Brien (4); D.Pollacco (1); E.Thrane (2); S.Poshyachinda (6); S.Mattila (7); L.Nuttall (8); E.Palle (9); A.Levan (1); T.Marsh (1); R.West (1); E.Stanway (1); B.Gompertz (1); K.Wiersema (1); ; K.Ackley (2); Y.-L.Mong (2); A.Casey (2); M.Brown (2); B.Muller (2); J.Mullaney (3); E.Daw (3); S.Littlefair (3); J.Maund (3); L.Makrygianni (3); R.Starling (4); R.Eyles (4); S.Tooke (4); S.Aukkaravittayapun (6); U.Sawangwit (6); S.Awiphan (6); D.Mkrtichian (6); P.Irawati (6); R.Kotak (7); T.Heikkila (7); E.Rol (2) (1) Warwick University, (2) Monash University, (3) University of Sheffield, (4) University of Leicester, (5) Armagh Observatory & Planetarium, (6) National Astronomical Research Institute of Thailand, (7) University of Turku, (8) University of Portsmouth, (9) Instituto de Astrofisica de Canarias), (10) Univ. of Manchester. report on behalf of the GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer prototype in response to S200115j (GCN #26759). Targeted observations started shortly after the preliminary event notification was received. These spanned 43 distinct tile pointings containing 59.6% of the source location probability (based on the initial BAYESTAR skymap) and were acquired between 04:34 UT Jan 15 2019 and 06:55 UT Jan 16 2019 (starting 11 minutes after the event time). Each pointing spans 4.9x3.7 square degrees and consisted of 3x60s exposures in our L-band filter (400-700nm passband similar to g+r) with a median 5-sigma photometric depth equivalent to g=19.5 for an individual pointing. Limits are based on a photometric calibration against PS1 sources. Most pointings were observed multiple times, typically 2-3 times. 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 following data acquisition and automated classifier cuts. For a small number of tiles no suitable reference frames were available, reducing the searched probability area to 51.7%. No new transients were detected that could be credibly associated with S200115j. We did not detect any significant sources at the location of the reported ZTF candidates (GCN #26767), as expected given our limiting magnitudes for those exposures. 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), The University of Portsmouth, the University of Turku and the Instituto de Astrofisica de Canarias (IAC) (https://goto-observatory.org/) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26797 SUBJECT: LIGO/Virgo S200115j: Upper limits from CALET observations. DATE: 20/01/17 10:07:53 GMT FROM: Yuta Kawakubo at Louisiana State U./CALET Y. Shimizu (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. Torii (Waseda U), T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), 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 S200115j T0 = 2020-01-15 04:23:09.742 UT (The LIGO Scientific Collaboration and Virgo Collaboration, GCN Circ. 26759), the CALET Gamma-ray Burst Monitor (CGBM) high voltages were off (from T0-5 min to T0+11 min). The CALET Calorimeter (CAL) was operating in the high energy trigger mode at the trigger time of S200115j. Using the CAL data, we have searched for gamma-ray events in the 10-100 GeV band from -60 sec to +60 sec from the GW trigger time and found no candidates in the overwrap region with the LIGO-Virgo high probability localization region. The 90% upper limit of CAL is 1.7 x 10^-6 erg/cm^2/s (10-100 GeV) when the summed LIGO-Virgo probability reaches 20%. The CAL FOV was centered at RA = 84.4 deg, DEC = +45.9 deg at T0. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26798 SUBJECT: LIGO/Virgo S200115j: Swift-XRT sources DATE: 20/01/17 10:58:20 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester), K.L. Page (U.Leicester), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), S.D. Barthelmy (NASA/GSFC), A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), A.A. Breeveld (UCL-MSSL), P. Brown (TAMU), 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), D. Hartmann (U. Clemson), H.A. Krimm (CRESST/GSFC/USRA), N.J. Klingler (PSU), 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. Birmingham), P.T. O'Brien (U. Leicester), J.P. Osborne (U. Leicester), C. Pagani (U. Leicester), M.J.Page (UCL-MSSL), 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 carried out 456 observations of the LVC error region for the GW trigger S200115j convolved with the 2MPZ catalogue (Bilicki et al. 2014, ApJS, 210, 9), using 23 fields from the 'bayestar' (version 0) GW localisation map and 433 fields from the 'bayestar' (version 2) GW localisation map. As these are 3D skymaps, galaxy distances were taken into account in selecting which ones to observe. The observations currently span from 7.1 ks to 164 ks after the LVC trigger, and the XRT has covered 28.5 deg^2 on the sky (corrected for overlaps). This covers 12% of the probability in the 'bayestar' (version 2) skymap, and 24% after convolving with the 2MPZ galaxy catalogue, as described by Evans et al. (2016, MNRAS, 462, 1591). Using the earlier 'bayestar' (version 0) skymap our observations cover 7.8% of the probability (16% when convolved). These pointings and associated metadata have been reported to the Treasure Map (Wyatt et al., arXiv 2001.00588; http://treasuremap.space/alerts?graceids=S200115j). 2 rank 2 sources have been found. These are candidates to be the counterpart to the GW trigger. Details of these sources are: Source S200115j_X130: ============= RA: 44.9028 ( = 02h 59m 36.67s) J2000 Dec: +7.4042 ( = +07d 24' 15.1") J2000 Error: 4.7 (arcsec, radius, 90% confidence). Peak Rate: 2.7e-02 +/- 6.9e-03 ct/sec (0.3-10 keV) Peak Flux: 1.2e-12 +/- 3.0e-13 erg cm^-2 s^-1 (0.3-10 keV) Catalogued: Yes Cat Source: 1WGA J0259.6+0724 in the ROSAT/WGACAT catalogue Separation: 6.5" from the XRT source Cat Rate: 4.9e-03 +/- 1.8e-03 ct/sec Cat Flux: 1.5e-13 +/- 5.5e-14 erg cm^-2 s^-1 (0.3-10 keV) So the source is 3.4-sigma above the catalogued flux. There is 1 GWGC or 2MPZ galaxy within 200 kpc of the source. The determination that this source has brightened compared to the ROSAT data is of course dependent on the assumed X-ray spectrum: if the source is heavily absorbed then the brightness increase becomes less noteworthy. Unfortunately, we have insufficient data to investigate the spectrum at the present time. Further observations are expected. Source S200115j_X136: ============= RA: 40.0508 ( = 02h 40m 12.19s) J2000 Dec: -2.5626 ( = -02d 33' 45.4") J2000 Error: 4.7 (arcsec, radius, 90% confidence). Peak Rate: 8.6e-02 +/- 1.7e-02 ct/sec (0.3-10 keV) Peak Flux: 3.7e-12 +/- 7.2e-13 erg cm^-2 s^-1 (0.3-10 keV) Catalogued: Yes Cat Source: 2SXPS J024012.0-023340 in the 2SXPS catalogue Separation: 4.9" from the XRT source Cat Rate: 6.7e-03 +/- 1.6e-03 ct/sec Cat Flux: 2.9e-13 +/- 6.9e-14 erg cm^-2 s^-1 (0.3-10 keV) so the source is 4.7-sigma above the catalogued flux. This source has been observed multiple times by Swift-XRT before, and its historical light curve can be seen at https://www.swift.ac.uk/2SXPS/2SXPS%20J024012.0-023340. This source is coincident with a 2MASS galaxy, and given the historical data, we assume that this galaxy is an AGN. Therefore the flux increase compared to previous Swift observations may simply reflect AGN activity, or may indicate a transient within that galaxy (as was the case for GW 170817, whose host galaxy was an X-ray emitter). Further observations are expected. In total, we have detected 14 X-ray sources. 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 https://www.swift.ac.uk/ranks.php. We have found: * 0 sources of rank 1 * 2 sources of rank 2 * 3 sources of rank 3 * 9 sources of rank 4 RANK 3 sources ============== These are uncatalogued X-ray sources, however they are not brighter than previous upper limits, so do not stand out as likely counterparts to the GW trigger. | Source ID | RA | Dec | Err90 | | S200115j_X62 | 02h 48m 23.89s | +05d 34' 46.4" | 4.5" | | S200115j_X63 | 02h 47m 25.18s | +05d 29' 41.7" | 7.0" | | S200115j_X135 | 02h 42m 11.50s | -03d 08' 13.8" | 28.4" | 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 ID | RA | Dec | Err90 | | S200115j_X40 | 02h 46m 14.64s | +05d 35' 29.9" | 4.5" | | S200115j_X73 | 02h 27m 0.61s | -04d 20' 20.3" | 6.9" | | S200115j_X74 | 02h 47m 27.22s | -00d 12' 21.5" | 3.9" | | S200115j_X75 | 02h 55m 14.42s | +09d 06' 26.6" | 8.3" | | S200115j_X76 | 02h 38m 27.56s | +01d 54' 29.5" | 4.8" | | S200115j_X105 | 03h 57m 45.52s | +41d 55' 07.9" | 5.0" | | S200115j_X106 | 03h 56m 57.58s | +42d 55' 44.3" | 4.4" | | S200115j_X127 | 02h 58m 51.32s | +06d 22' 26.4" | 5.2" | | S200115j_X134 | 02h 42m 40.74s | +00d 57' 31.5" | 4.8" | For all flux conversions and comparisons with catalogues and upper limits from other missions, we assumed a power-law spectrum with NH=3x10^20 cm^-2, and photon index (Gamma)=1.7 The results of the XRT automated analysis, including details of the sources listed above, are online at https://www.swift.ac.uk/LVC/S200115j This circular is an official product of the Swift XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26807 SUBJECT: LIGO/Virgo S200115j: Updated Sky Localization and source properties DATE: 20/01/17 18:50:16 GMT FROM: Deep Chatterjee at University of Wisconsin, Milwaukee The LIGO Scientific Collaboration and the Virgo Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S200115j (GCN Circular 26759). Parameter estimation has been performed using LALInference [1] and a new sky map, LALInference.fits.gz,0, distributed via GCN Notice, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S200115j/files/ The preferred sky map at this time is LALInference.fits.gz,0. For the LALInference.fits.gz,0 sky map, the 90% credible region is 765 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 340 +/- 79 Mpc (a posteriori mean +/- standard deviation). Based on posterior support from parameter estimation [1], under the assumption that the candidate is astrophysical in origin, the probability that the lighter compact object has a mass < 3 solar masses (HasNS) is >99%. Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is >99%. Note: the sequence of three Preliminary Notices on January 15, 2020 for this candidate was due to a manual change in the "preferred event". The MBTAOnline pipeline found the largest signal-to-noise ratio (SNR) and thus provided the first preferred event, as indicated in the first two Preliminary Notices. However, the preferred event was manually changed to a GstLAL trigger (with nearly the same SNR) because of a possible discrepancy noted in the low-latency Bayestar sky maps calculated for the two triggers. The third Preliminary Notice reflected that change. For further information about analysis methodology including “preferred events”, refer to the LIGO/Virgo Public Alerts User Guide . [1] Veitch et al. PRD 91, 042003 (2015) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26808 SUBJECT: LIGO/Virgo S200115j: Swift/UVOT observations of Swift/XRT S200115j_X136 DATE: 20/01/17 22:24:22 GMT FROM: Samantha Oates at MSSL S. R. Oates (U. of Birmingham), A. A. Breeveld (MSSL-UCL), N. P. M. Kuin (UCL-MSSL), F. E. Marshall (NASA/GSFC), P. Brown (TAMU), M. De Pasquale (Istanbul U.), C. Gronwall (PSU), M. J. Page (UCL-MSSL), 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.), K. L. Page (U.Leicester), J. A. Kennea (PSU), N. J. Klingler (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), 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 (U Toronto), and E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift team: We report Swift/UVOT observations of S200115j_X136 (Evans et al., GCN Circ. 26798), a rank 2 XRT source found during the search for the EM counterpart of the LVC event S200115j (LIGO/VIRGO Collaboration GCN Circ. 26759). Swift/UVOT took a 75s u-band exposure 17.7 hours after the LIGO/VIRGO trigger (LIGO/VIRGO Collaboration GCN Circ. 26759) we obtain a u-band magnitude of 16.54 +/- 0.07. Comparing this to archival UVOT measurements (u = 17.04 +/- 0.07 mag; July 2012), we find S200115j_X136 has brightened by 0.5 magnitudes. As noted by Evans et al., (GCN Circ. 26798), S200115j_X136 is consistent with a 2MASS galaxy. Therefore the flux increase compared to previous Swift observations may reflect AGN activity, or may indicate a transient within that galaxy. Preliminary magnitudes were determined using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) and have not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.03 along the line of sight (Schlegel et al. 1998). This circular is an official product of the Swift team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26814 SUBJECT: LIGO/Virgo S200115j: NIR upper limits for ZTF20aafqvyc/AT2020yq from the Palomar 200-inch telescope DATE: 20/01/18 17:39:24 GMT FROM: Kishalay De at Caltech, GROWTH K. De (Caltech), M. Hankins (Caltech), M. M. Kasliwal (Caltech) report on behalf of the ZTF and GROWTH collaborations We obtained J and Ks band imaging of ZTF20aafqvyc/AT2020yq (Anand et al. GCN 26767) found in the localization region of LIGO/Virgo S200115j (GCN 26759, GCN 26807) with the Wide Field Infrared Camera (WIRC; Wilson et al. 2003) on the Palomar 200-inch telescope. We obtained a series of dithered exposures of the target on UT 2020-01-18 for a total exposure time of 900 s in J band and 600 s in Ks band. The data were reduced and stacked with a custom data reduction pipeline (De et al. 2020). No source is detected at the source location down to 5 sigma limiting magnitude of J = 21.5 AB mag and Ks = 20.9 AB mag. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26817 SUBJECT: LIGO/Virgo S200115j: LCO upper limits for ZTF20aafqvyc/AT2020yq from the McDonald Observatory 1-m telescope DATE: 20/01/19 17:27:35 GMT FROM: Tomas Ahumada at U. of Maryland Tomas Ahumada (UMD), Michael Coughlin (UMinn), Shreya Anand (Caltech) report on behalf of the ZTF and GROWTH collaborations On UT 2020-01-19, we imaged ZTF20aafqvyc/AT2020yq (Anand et al. GCN 26767) found in the localization region of LIGO/Virgo S200115j (GCN 26759, GCN 26807) with the Sinistro camera on the 1-m LCO Global Telescope Network (LCOGT, Brown et al., 2013). We obtained a series of 3 exposures of 300 s in g-, r- and i-bands. After stacking the data, no source is detected at the source location down to a 3 sigma limits of g = 22.6 AB mag , r = 21.8 AB mag and i = 20.9 AB mag. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26819 SUBJECT: LIGO/Virgo S200115j: Mondy upper limits for ZTF20aafqvyc/AT2020yq DATE: 20/01/19 18:19:59 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), A. Pozanenko (IKI), S. Belkin (IKI), E. Klunko (ISTP), A. Volnova (IKI) report on behalf of GRB IKI FuN: We observed the ZTF20aafqvyc/AT2020yq (Anand et al., GCN 26767) found in the localization region of LIGO/Virgo S200115j (GCN 26759, GCN 26807) with AZT-33IK telescope of Sayan observatory (Mondy) in two epochs. We do not detect any source at the coordinates the ZTF20aafqvyc/AT2020yq (Anand et al., GCN 26767). Preliminary photometry of the field is following Date UT start MJD Filter Exp. OT Err. UL(3sigma) (mid, days) (s) 2020-01-15 17:21:36 58863.73028 R 10*120 n/d n/d 21.6 2020-01-16 17:10:33 58864.72261 R 10*120 n/d n/d 22.1 The photometry is based on the nearby USNO-B1.0 stars USNO-B1.0 R2 1284-0073552 17.62 1284-0073507 18.38 1284-0073562 17.98 1284-0073542 16.97 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26820 SUBJECT: LIGO/Virgo S200115j : No significant candidates in TAROT - FRAM - GRANDMA observations DATE: 20/01/19 21:10:56 GMT FROM: Kanthanakorn Noysena at GRANDMA-n-TAROT K. Noysena (Artemis, IRAP), S. Antier (APC), M. Blazek (HETH/IAA-CSIC), P. Hello (IJCLab), E. Howell (OzGrav-UWA), Karpov (FZU), M. Masek (FZU), M. Prouza (FZU), M. Boer (Artemis), N. Christensen (Artemis), L. Eymar (Artemis), A. Klotz (IRAP), A. Coleiro (APC), D. Corre (IJCLab), M. Coughlin (UMN), D. Coward (OzGrav-UWA), J.G. Ducoin (IJCLab), B. Gendre (OzGrav-UWA), D. A. Kann (HETH/IAA-CSIC), N. Kochiashvili (Iliauni), C. Lachaud (APC), N. Leroy (IJCLab), C. Thoene (HETH/IAA-CSIC), D. Turpin (AIM-CEA), X. Wang (THU) report on behalf of the FRAM, TAROT and GRANDMA collaborations. We performed tiled observations of LIGO/Virgo S200115j event (#GCN26759) with the FRAM-Auger, FRAM-CTA-N, TAROT-Calern (TCA), TAROT-Chili (TCH), TAROT-Reunion (TRE) telescopes. FRAM-Auger is located at Pierre Auger Observatory. FRAM-CTA-N is located at Observatorio del Roque de los Muchachos. TCA is located at Calern site at the Cote d'Azur observatory. TCH is located at La Silla ESO observatory (LaS/ESO). TRE is located at Les Makes astronomical observatory. The following table shows for each telescope: the delay in minutes from the trigger, which filter is used, the field of view of the telescope in degrees and the typical limiting magnitude (AB mag) for a given exposure in seconds (s). +-------------+---------+----------+-------------+------------+ | Telescope | Delay | Filter | f.o.v. | Limiting | | | [min] | | [deg] | Mag. | |-------------+---------+----------+-------------+------------| | FRAM-Auger | 1247 | R | 1.0 x 1.0 | 18.0 (60s) | | FRAM-CTA-N | 916 | R | 0.45 x 0.45 | 17.0 (90s) | | TCA | 771 | Clear | 1.9 x 1.9 | 18.0 (60s) | | TCH | 16 | Clear | 1.9 x 1.9 | 18.0 (60s) | | TRE | 704 | Clear | 4.2 x 4.2 | 17.0 (60s) | +-------------+---------+----------+-------------+------------+ We performed the following joint tiled observations [1] : +-------------+------------+------------+---------+---------+---------+ | Telescope | TStart | TEnd | RA | DEC | Proba | | | [UTC] | [UTC] | [deg] | [deg] | [%] | |-------------+------------+------------+---------+---------+---------| | FRAM-Auger | 2020-01-16 | 2020-01-16 | 43.784 | 2.432 | 0.1 | | | 01:09:24 | 01:13:51 | | | | | FRAM-Auger | 2020-01-16 | 2020-01-16 | 44.878 | 5.351 | 0.1 | | | 01:14:29 | 01:18:56 | | | | | FRAM-Auger | 2020-01-16 | 2020-01-16 | 44.757 | 4.378 | <0.1 | | | 01:19:31 | 01:23:58 | | | | | FRAM-Auger | 2020-01-16 | 2020-01-16 | 43.666 | 1.460 | <0.1 | | | 01:24:35 | 01:29:02 | | | | | FRAM-Auger | 2020-01-16 | 2020-01-16 | 43.784 | 3.405 | 0.2 | | | 01:29:38 | 01:34:05 | | | | | FRAM-Auger | 2020-01-16 | 2020-01-16 | 42.695 | 0.486 | <0.1 | | | 01:34:40 | 01:39:07 | | | | | FRAM-Auger | 2020-01-16 | 2020-01-16 | 42.695 | -0.486 | <0.1 | | | 01:39:44 | 01:44:11 | | | | | FRAM-Auger | 2020-01-16 | 2020-01-16 | 44.757 | 3.405 | <0.1 | | | 01:44:49 | 01:49:16 | | | | | FRAM-Auger | 2020-01-16 | 2020-01-16 | 42.695 | 1.460 | 0.1 | | | 01:49:52 | 01:54:19 | | | | | FRAM-Auger | 2020-01-16 | 2020-01-16 | 41.725 | -1.460 | <0.1 | | | 01:54:55 | 01:59:22 | | | | | FRAM-Auger | 2020-01-16 | 2020-01-16 | 43.666 | 0.486 | <0.1 | | | 01:59:58 | 02:04:25 | | | | | FRAM-Auger | 2020-01-16 | 2020-01-16 | 44.757 | 2.432 | <0.1 | | | 02:05:03 | 02:09:30 | | | | | FRAM-Auger | 2020-01-16 | 2020-01-16 | 42.811 | 2.432 | 0.2 | | | 02:10:07 | 02:14:34 | | | | | FRAM-Auger | 2020-01-16 | 2020-01-16 | 43.784 | 4.378 | 0.2 | | | 02:15:10 | 02:19:38 | | | | | FRAM-Auger | 2020-01-16 | 2020-01-16 | 41.725 | -0.486 | <0.1 | | | 02:20:14 | 02:24:41 | | | | | FRAM-Auger | 2020-01-16 | 2020-01-16 | 41.838 | -2.432 | <0.1 | | | 02:25:17 | 02:29:44 | | | | | FRAM-Auger | 2020-01-16 | 2020-01-16 | 45.730 | 4.378 | <0.1 | | | 02:30:20 | 02:34:47 | | | | | FRAM-Auger | 2020-01-16 | 2020-01-16 | 42.695 | -1.460 | <0.1 | | | 02:35:23 | 02:39:50 | | | | | FRAM-Auger | 2020-01-16 | 2020-01-16 | 40.865 | -3.405 | <0.1 | | | 02:40:25 | 02:44:52 | | | | | FRAM-Auger | 2020-01-16 | 2020-01-16 | 45.978 | 6.324 | <0.1 | | | 02:45:30 | 02:49:57 | | | | | ----- | ----- | ----- | ----- | ----- | ----- | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 42.604 | 0.225 | <0.1 | | | 19:38:25 | 19:42:31 | | | | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 43.041 | 0.225 | <0.1 | | | 19:42:46 | 19:46:52 | | | | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 43.530 | 2.846 | <0.1 | | | 19:47:07 | 19:51:13 | | | | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 43.967 | 3.720 | <0.1 | | | 19:51:33 | 19:55:39 | | | | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 43.477 | 1.099 | <0.1 | | | 19:56:10 | 20:00:15 | | | | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 44.405 | 2.846 | <0.1 | | | 20:00:31 | 20:04:37 | | | | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 43.967 | 2.846 | <0.1 | | | 20:04:57 | 20:09:03 | | | | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 44.459 | 4.157 | <0.1 | | | 20:09:18 | 20:13:24 | | | | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 43.041 | 1.099 | <0.1 | | | 20:13:40 | 20:17:46 | | | | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 44.405 | 3.720 | <0.1 | | | 20:18:01 | 20:22:07 | | | | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 43.477 | 1.536 | <0.1 | | | 20:22:22 | 20:26:28 | | | | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 43.914 | 2.409 | <0.1 | | | 20:26:49 | 20:30:55 | | | | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 43.477 | 1.973 | <0.1 | | | 20:31:09 | 20:35:15 | | | | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 43.914 | 1.973 | <0.1 | | | 20:35:30 | 20:39:36 | | | | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 43.041 | 1.536 | <0.1 | | | 20:39:56 | 20:44:02 | | | | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 43.477 | 2.409 | <0.1 | | | 20:44:17 | 20:48:23 | | | | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 42.604 | -0.212 | <0.1 | | | 20:48:43 | 20:52:49 | | | | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 43.041 | 1.973 | <0.1 | | | 20:53:04 | 20:57:10 | | | | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 44.897 | 4.594 | <0.1 | | | 20:57:25 | 21:01:31 | | | | | FRAM-CTA-N | 2020-01-15 | 2020-01-15 | 44.897 | 4.157 | <0.1 | | | 21:01:45 | 21:05:51 | | | | | ----- | ----- | ----- | ----- | ----- | ----- | | TCA | 2020-01-15 | 2020-01-18 | 41.565 | -1.833 | 0.2 | | | 17:13:13 | 17:50:17 | | | | | TCA | 2020-01-15 | 2020-01-19 | 43.411 | 3.733 | 0.6 | | | 17:19:57 | 18:56:02 | | | | | TCA | 2020-01-15 | 2020-01-19 | 40.825 | -3.689 | 0.2 | | | 17:26:42 | 19:02:48 | | | | | TCA | 2020-01-15 | 2020-01-19 | 61.353 | 40.372 | 0.2 | | | 17:39:07 | 01:45:45 | | | | | TCA | 2020-01-15 | 2020-01-19 | 63.019 | 42.703 | 0.2 | | | 17:45:52 | 19:21:58 | | | | | TCA | 2020-01-15 | 2020-01-19 | 65.502 | 42.703 | <0.1 | | | 18:57:13 | 18:03:46 | | | | | TCA | 2020-01-15 | 2020-01-19 | 43.411 | 1.878 | 0.4 | | | 19:30:32 | 18:36:52 | | | | | TCA | 2020-01-15 | 2020-01-19 | 45.011 | 5.114 | 0.4 | | | 19:37:16 | 18:43:37 | | | | | TCA | 2020-01-15 | 2020-01-19 | 149.185 | 70.538 | <0.1 | | | 20:02:59 | 19:09:33 | | | | | TCA | 2020-01-15 | 2020-01-19 | 68.981 | 50.125 | 0.2 | | | 20:35:38 | 02:11:38 | | | | | TCA | 2020-01-15 | 2020-01-19 | 64.479 | 46.414 | 0.3 | | | 21:21:03 | 17:57:02 | | | | | TCA | 2020-01-15 | 2020-01-19 | 71.770 | 51.981 | 0.1 | | | 22:59:06 | 19:35:26 | | | | | TCA | 2020-01-16 | 2020-01-19 | 74.796 | 53.837 | <0.1 | | | 02:14:06 | 20:16:13 | | | | | TCA | 2020-01-16 | 2020-01-19 | 64.780 | 44.558 | 0.2 | | | 03:52:07 | 19:28:43 | | | | | TCA | 2020-01-16 | 2020-01-19 | 71.719 | 53.837 | 0.2 | | | 04:31:07 | 17:37:52 | | | | | TCA | 2020-01-16 | 2020-01-19 | 71.816 | 50.125 | <0.1 | | | 04:37:45 | 20:13:47 | | | | | TCA | 2020-01-17 | 2020-01-19 | 69.132 | 48.270 | <0.1 | | | 00:12:06 | 19:47:51 | | | | | TCA | 2020-01-17 | 2020-01-19 | 63.769 | 40.847 | <0.1 | | | 00:24:29 | 20:01:21 | | | | | TCA | 2020-01-17 | 2020-01-19 | 67.126 | 46.414 | 0.1 | | | 20:18:19 | 19:54:37 | | | | | TCA | 2020-01-18 | 2020-01-19 | 42.937 | 0.022 | 0.2 | | | 17:23:44 | 18:30:06 | | | | | ----- | ----- | ----- | ----- | ----- | ----- | | TCH | 2020-01-15 | 2020-01-19 | 44.367 | 3.677 | 0.4 | | | 04:39:08 | 03:34:39 | | | | | TCH | 2020-01-15 | 2020-01-19 | 43.892 | 1.859 | 0.3 | | | 04:45:45 | 01:13:33 | | | | | TCH | 2020-01-15 | 2020-01-19 | 42.083 | -1.777 | 0.2 | | | 04:58:16 | 01:25:58 | | | | | TCH | 2020-01-15 | 2020-01-19 | 41.133 | -3.595 | 0.1 | | | 05:05:02 | 04:02:44 | | | | | TCH | 2020-01-15 | 2020-01-18 | 258.202 | -27.707 | <0.1 | | | 08:28:57 | 09:01:24 | | | | | TCH | 2020-01-16 | 2020-01-16 | 45.226 | 5.495 | 0.4 | | | 00:43:42 | 00:50:01 | | | | | TCH | 2020-01-16 | 2020-01-18 | 37.990 | -0.909 | 0.2 | | | 02:00:58 | 04:07:19 | | | | | TCH | 2020-01-16 | 2020-01-19 | 49.700 | 15.455 | <0.1 | | | 02:13:57 | 02:50:20 | | | | | TCH | 2020-01-16 | 2020-01-19 | 34.783 | -12.686 | <0.1 | | | 02:20:44 | 02:54:55 | | | | | TCH | 2020-01-16 | 2020-01-18 | 47.825 | 15.455 | 0.2 | | | 02:27:29 | 04:33:51 | | | | | TCH | 2020-01-16 | 2020-01-19 | 42.558 | 0.041 | 0.3 | | | 02:53:47 | 03:25:43 | | | | | TCH | 2020-01-16 | 2020-01-16 | 259.916 | -25.414 | 0.5 | | | 08:32:41 | 08:39:00 | | | | | TCH | 2020-01-16 | 2020-01-19 | 270.384 | -36.323 | 0.5 | | | 08:39:26 | 09:13:34 | | | | | TCH | 2020-01-16 | 2020-01-18 | 259.603 | -23.595 | 0.4 | | | 08:52:04 | 08:24:23 | | | | | TCH | 2020-01-18 | 2020-01-19 | 268.120 | -36.323 | 0.1 | | | 08:15:34 | 09:18:09 | | | | | TCH | 2020-01-18 | 2020-01-18 | 257.786 | -21.777 | 0.2 | | | 08:41:36 | 08:43:36 | | | | | TCH | 2020-01-18 | 2020-01-18 | 271.111 | -34.505 | 1.3 | | | 08:52:39 | 08:54:39 | | | | | ----- | ----- | ----- | ----- | ----- | ----- | | TRE | 2020-01-15 | 2020-01-16 | 50.233 | 12.273 | 0.2 | | | 16:06:14 | 17:12:32 | | | | | TRE | 2020-01-15 | 2020-01-16 | 61.714 | 36.818 | 0.3 | | | 16:31:50 | 17:38:22 | | | | | TRE | 2020-01-15 | 2020-01-16 | 49.091 | 4.091 | <0.1 | | | 16:45:02 | 17:51:25 | | | | | TRE | 2020-01-15 | 2020-01-16 | 56.104 | 28.636 | 0.3 | | | 17:31:22 | 18:35:33 | | | | | TRE | 2020-01-15 | 2020-01-16 | 45.000 | 4.091 | 1.5 | | | 19:24:18 | 20:30:33 | | | | | TRE | 2020-01-15 | 2020-01-15 | 40.909 | 0.000 | 2.0 | | | 19:37:21 | 19:43:37 | | | | | TRE | 2020-01-15 | 2020-01-15 | 46.047 | 12.273 | 1.8 | | | 20:15:43 | 20:22:00 | | | | | TRE | 2020-01-16 | 2020-01-16 | 41.379 | -8.182 | <0.1 | | | 16:08:50 | 16:10:50 | | | | | TRE | 2020-01-16 | 2020-01-16 | 56.571 | 36.818 | 1.1 | | | 18:10:07 | 18:16:23 | | | | | TRE | 2020-01-16 | 2020-01-16 | 45.000 | 0.000 | 0.3 | | | 20:49:41 | 20:51:41 | | | | +-------------+------------+------------+---------+---------+---------+ TStart and TEnd refers respectively to the time of the first and last exposure for a given tile. Observations are not necessarily continuous in this interval. The Probability refers to the 2D spatial probability of the GW skymap enclosed in a given tile. These observations cover about 13.2% of the cumulative probability of the LALInference skymap created on 2020-01-17 13:54:56 (UTC). The coverage map is available at: https://grandma-owncloud.lal.in2p3.fr/index.php/s/XgtMhPRxcyL09gR/download?path=%2F&files=GRANDMA_S200115j_1579467054.png No significant transient candidates were found during our low latency analysis [2,3]. 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 [2](https://grandma.lal.in2p3.fr/). Details on the different telescopes are available on the GRANDMA web pages. [1] M. W Coughlin et al., MNRAS 2019, https://doi.org/10.1093/mnras/stz2485 [2] S. Antier et al., MNRAS 2019, https://doi.org/10.1093/mnras/stz3142 [3] K. Noysena et al., ApJ 2019, arXiv:1910.02770 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26822 SUBJECT: LIGO/Virgo S200115j: GMOS-N upper limits for ZTF20aafqvyc/AT2020yq from the Gemini Observatory DATE: 20/01/20 03:23:40 GMT FROM: Tomas Ahumada at U. of Maryland Tomas Ahumada (UMD), Leo Singer (NASA GSFC) report on behalf of the ZTF and GROWTH collaborations On UT 2020-01-19, we imaged ZTF20aafqvyc/AT2020yq (Anand et al. GCN 26767) found in the localization region of LIGO/Virgo S200115j (GCN 26759, GCN 26807) with the Gemini Multi-Object Spectrographs (GMOS-N) mounted on the Gemini-North 8-meter telescope on Mauna Kea. We combined four g- band 200s exposures using DRAGONS, a Python-base data reduction platform provided by the Gemini Observatory. No source is detected at the source location down to a 3 sigma limits of g = 24.5 AB mag. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26823 SUBJECT: LIGO/Virgo S200115j: No counterpart detection within possible host galaxies observed by the GRAWITA-Savelli telescope DATE: 20/01/20 09:45:43 GMT FROM: Sandra Savaglio at U. of Calabria A. Brosio (Osservatorio Astronomico Lilio), S. Massaro (Osservatorio Astronomico Noto) L. Nicastro (INAF-OAS), E. Palazzi (INAF-OAS), S. Savaglio (UNICAL), report on behalf of GRAWITA: We carried out optical observations of 12 of the potential host galaxies visible in the Northern hemisphere of LVC trigger S200115j reported by P.A. Evans (GCN 26756). Each galaxy was observed for 10 minutes in the r-sdss filter with the 0.5m telescope of the Osservatorio Astronomico Lilio, located in Savelli (South Italy) on 2020-01-15 starting at 17:24:39 UT. Visual inspection of the 12 fields does not reveal any new candidate compared with Pan-STARRS archival images down to r~20.5 mag (3-sigma, AB). Additional observations have been acquired, the analysis is underway. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26839 SUBJECT: LIGO/VIRGO S200115j: No obvious candidates from Pan-STARRS2 observations DATE: 20/01/21 15:55:18 GMT FROM: Shubham Srivastav at QUB S. Srivastav, S. J Smartt (QUB), M. Huber (IfA, Univ. of Hawaii), K. W. Smith (QUB), K. Chambers, A. Schulz (IfA), D. R. Young, O. McBrien, J. Gillanders, D. O'Neil, P. Clark, S. Sim (QUB), T. de Boer, J. Bulger, J. Fairlamb, M. Huber, C.-C. Lin, T. Lowe, E. Magnier, R. J. Wainscoat, M. Willman (IfA, Univ. of Hawaii), T.-W, Chen (Stockholm), A. Rest (STScI), C. Stubbs (Harvard) We report observations of the skymap of the mass gap event S200115j (LVC, GCN 26759). We targeted one of the eastern lobes in the Lal Inference probability region (RA ~ 3 hr) with the Pan-STARRS2 telescope. The images were obtained in the w-band (Tonry et al. 2012, ApJ 750, 99). A sequence of quads (4 x 45 sec) was taken at each pointing position during the nights of 2020-01-18 and 2020-01-19. 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) 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 report the following transients within the 90% contour of the skymap. All the candidates are offset from a clear galaxy. PS20ev and PS20fr have spectroscopic host redshifts (from NED), while the rest have photometric redshifts from GLADE or SDSS. The GW event was reported by LVC on MJD 58863.18. Name TNS Name RA (J2000) Dec (J2000) Disc. MJD Disc. Mag redshift PS20ev AT2020ait 02:36:56.51 -02:12:03.5 58866.30 20.23 0.0701 (s) PS20fs AT2020ajy 02:53:21.00 +03:23:17.4 58866.32 21.46 0.301 (p) PS20fo AT2020ajw 02:25:53.75 -03:13:04.6 58866.30 19.90 0.138 (p) PS20fr AT2020ajx 02:25:23.51 -07:50:15.5 58866.30 20.42 0.0538 (s) PS20fu AT2020ajz 02:49:02.17 +04:59:11.6 58866.30 21.16 - PS20fv AT2020aka 02:37:24.50 -01:09:20.1 58867.26 19.91 0.142 (p) PS20fw AT2020akb 03:10:05.41 +05:59:16.4 58867.32 21.05 0.098 (p) PS20fx AT2020akc 02:52:35.05 +07:15:11.9 58866.30 20.89 - Only PS20fs (AT2020ajy) shows a ~0.5 mag rise, the other transients show a flat w-band light curve. There are no obvious candidates that show rapid fading. The LVC distance of 332 +/- 78 Mpc corresponds to 0.06 < z < 0.09 (for Ho = 70). We also recover the following transients discovered by the ATLAS and ZTF surveys after the GW event. Our photometry does not indicate any unusual rise or fade. Source TNS Name RA (J2000) Dec (J2000) MJD PS2 Mag redshift ATLAS AT2020afo 02:27:31.13 -01:06:41.6 58867.26 18.61 0.0857 (s) ZTF AT2020agw 02:34:02.13 -04:26:44.3 58866.30 20.62 - ZTF AT2020aeo 02:59:39.07 +06:41:11.2 58867.25 20.89 - //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26849 SUBJECT: LIGO/Virgo S200115j: Upper limits from Konus-Wind observations DATE: 20/01/22 07:28:50 GMT FROM: Anna Ridnaia at Ioffe Institute A. Ridnaia, S. Golenetskii, R.Aptekar, D. Frederiks, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, 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 S200115j (2020-01-15 04:23:09.742 UTC, hereafter T0; LIGO/Virgo Collaboration GCN Circ. 26759). No triggered KW GRBs happened ~1 day before and ~17 hours after T0. The closest waiting-mode GRB was observed ~3 hours after 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 9.3x10^-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 2.8x10^-7 erg/cm^2/s (20 - 1500 keV, 2.944 s scale). All the quoted values are preliminary. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26855 SUBJECT: LIGO/Virgo S200115j: Further Swift-XRT sources DATE: 20/01/22 16:27:48 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester), K.L. Page (U.Leicester), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), S.D. Barthelmy (NASA/GSFC), A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), A.A. Breeveld (UCL-MSSL), P. Brown (TAMU), 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), D. Hartmann (U. Clemson), H.A. Krimm (CRESST/GSFC/USRA), N.J. Klingler (PSU), 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. Birmingham), P.T. O'Brien (U. Leicester), J.P. Osborne (U. Leicester), C. Pagani (U. Leicester), M.J.Page (UCL-MSSL), 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 continued to observe the LIGO/Virgo event S200115j (GCN Circ. 26759). The XRT data cover 36.1 deg^2 covering 16% of the probability in the 'bayestar' (version 2) skymap (after convolution with 2MPZ galaxies), but only 10% of the probability from the 'LALInference' skymap (also after convolution with 2MPZ), due to the shift of probability towards the southern lobe in the latter map; this lobe is too close to the Sun to allow Swift observations. Observations were carried out in two phases; initial observations of 80 s per field, then a second pass with 500 s per field. These pointings and associated metadata have been reported to the Treasure Map (Wyatt et al., arXiv 2001.00588; http://treasuremap.space/alerts?graceids=S200115j). In total we have detected 146 X-ray sources, which can be viewed at https://www.swift.ac.uk/LVC/83/. 84 of these are uncatalogued in X-rays but with fluxes consistent with historical upper limits. 53 are known X-ray sources whose fluxes are consistent with historical values. 9 further sources were identified as being of potential interest (rank 2; see https://www.swift.ac.uk/ranks.php). The table below gives the basic details of the sources; further comments are below. | Source ID | RA | Dec | Err90 | Note | | S200115j_X130 | 02h 59m 36.73s | +07d 24' 13.9" | 5.2" | 4 | | S200115j_X136 | 02h 40m 12.18s | -02d 33' 45.6" | 5.2" | 1 | | S200115j_X487 | 02h 41m 59.74s | -03d 05' 23.0" | 4.8" | 5 | | S200115j_X488 | 02h 40m 53.34s | -03d 25' 12.0" | 6.2" | 4 | | S200115j_X707 | 02h 55m 31.95s | +12d 45' 26.6" | 4.5" | 2 | | S200115j_X717 | 02h 23m 42.05s | -04d 35' 36.2" | 4.5" | 4 | | S200115j_X745 | 02h 24m 04.01s | -04d 33' 05.6" | 5.1" | 5 | | S200115j_X746 | 03h 00m 13.78s | +03d 49' 53.8" | 5.1" | 3 | | S200115j_X748 | 02h 25m 37.24s | -05d 01' 07.2" | 5.9" | 4 | Note 1) Of these, sources S200115j_X136, S200115j_X707 and S200115j_X746 are those we deem most worthy of further investigation. S200115j_X136 is a known X-ray source, observed several times in the past by Swift (see https://www.swift.ac.uk/2SXPS/2SXPS%20J024012.0-023340). In our GW follow up observations it is a factor of ~10 brighter than in our historical dataset, but with no signs of variability between our two epochs of GW follow up (data collected at ~100 ks and 300ks after the GW trigger). As reported by Oates et al (GCN Circ. 26808) the UVOT data also show an increase in flux compared to historical data. This source is 1.5" from the 2MASS galaxy 2MASX J02401221-0233438, which SIMBAD reports as having z=0.04; making its distant consistent with the GW-predicted distance along this line of sight at the ~1.1-sigma level. If the X-ray source is in this galaxy its observed 0.3-10 keV luminosity is ~3 x 10^43 erg cm^-2 s^-1. A Vizier search reveals no AGN catalogues containing this source. Note 2) S200115j_X707 is uncatalogued in X-rays and in our initial detection is ~3.5 sigma above the historical 3-sigma upper limit from the RASS. It also faded strongly between observations taken at 160 ks after the GW trigger and at 390 ks after the trigger. A Vizier search reveals no AGN catalogues containing this source. This source was only flagged as "reasonable" by our source detection system, which means the probability that it is a spurious detection is ~7%. Note 3) S200115j_X746 is also uncatalogued and in the first observation (7.3 ks after the GW trigger) was 4.7 sigma above the historical 3-sigma upper limit from the RASS. A further observation at 510 ks after the GW trigger showed the source to have faded by a factor of ~15. A Vizier search reveals no AGN catalogues containing this source. Note 4) Sources S200115j_X130, S200115j_X717 and S200115j_X748 are all known X-ray sources whose flux in our GW follow-up observations is increased compared to historical data; the latter two have previously been observed with Swift and have elevated fluxes compared to those previous datasets. However, all of these sources have been identified with AGN, and are thus likely to indicate AGN activity although a transient within the AGN cannot immediately be ruled out. S200115j_X488 is similar except that it is not a known X-ray emitter. Its current flux is 3.5-sigma above catalogued values; and it shows strong evidence of fading, however it corresponds to a source identified as an AGN in the WISE AGN candidates catalogs (Assef et al., 2018) and therefore may simply be a variable AGN. Further observations of all of these sources are planned. Note 5) Sources S200115j_X487 and S200115j_X745 are, upon manual investigation, considered unlikely to be counterparts since their classification as such depends upon a single, short-exposure data point. For S200115j_X487 this datapoint is during a time of very high background and is unreliable. S200115j_X745 is coincident with Mkn 1036, and only one datapoint from our recent observations is above the historical XMM flux. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26863 SUBJECT: LIGO/Virgo S200115j: Zwicky Transient Facility search for optical counterparts to Swift X-ray sources DATE: 20/01/23 05:39:23 GMT FROM: Igor Andreoni at Caltech Igor Andreoni (Caltech), Mansi M. Kasliwal (Caltech), S. Brad Cenko (NASA GSFC), Yuhan Yao (Caltech) On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations The Zwicky Transient Facility (ZTF; Graham et al. 2019, Bellm et al. 2019) has repeatedly observed the location of nine X-ray sources, found with the Neil Gehrels Swift Observatory (Swift), that Evans et al. (GCN #26855) reported as candidate counterparts to S200115j (GCN #26759, GCN #26807) with rank = 2. We searched the ZTF alert database using Kowalski (Duev et al., 2019). We found that only the Swift source S200115j_X136 has a ZTF alert within the spatial uncertainty indicated in GCN #26855. The ZTF source, labelled ZTF20aafapey, was found on 2020-01-13 (before the detection of S200115j) and it is located on top of the nucleus of the galaxy 2MASS 02401222-0233442 at redshift z=0.04333 (6dF Galaxy Survey; Jones et al., 2009). We performed forced photometry of ZTF20aafapey using ForcePhotZTF (Yao et al., 2019). The light curve (Table 1) shows rapid variability days before S200115j, with a significant brightening of >0.5 mag on 2020-01-13. Our results are in agreement with Oates et al. (GCN #26808) and further suggest that S200115j_X136/ZTF20aafapey is caused by AGN activity. We conclude that S200115j_X136 is unlikely associated with S200115j. Table 1: Light curve of ZTF20aafapey +---------------------+------+------+-----+ | date_obs |filter| mag | err | +---------------------+------+------+-----+ | 2020-01-12 04:52:53 | r | 19.4 | 0.1 | | 2020-01-13 04:15:19 | r | 19.5 | 0.1 | | 2020-01-13 04:15:59 | r | 19.3 | 0.1 | | 2020-01-13 04:43:20 | r | 19.5 | 0.2 | | 2020-01-13 04:43:59 | r | 18.9 | 0.1 | | 2020-01-13 05:28:55 | r | 19.5 | 0.2 | | 2020-01-13 05:29:33 | r | 19.0 | 0.1 | +---------------------+------+------+-----+ For other Swift X-ray sources no ZTF alerts were issued, although the transient candidate locations were recently observed in most cases. In Table 2 we report ZTF detection upper limits at the approximate location of the Swift sources - other than S200115j_X136 - from 2020-01-13 to 2020-01-22. The exposure times are provided in seconds. Table 2: ZTF upper limits +---------------+---------------------+---------+--------+----------+ | source_name | date_obs | exptime | filter | maglimit | +---------------+---------------------+---------+--------+----------+ | S200115j_X130 | 2020-01-13 02:28:48 | 30 | g | >20.6 | | S200115j_X130 | 2020-01-13 02:29:28 | 30 | g | >20.5 | | S200115j_X130 | 2020-01-15 03:12:49 | 30 | g | >20.9 | | S200115j_X130 | 2020-01-15 06:34:05 | 300 | g | >20.7 | | S200115j_X130 | 2020-01-18 05:45:35 | 300 | g | >21.3 | | S200115j_X136 | 2020-01-13 04:15:20 | 30 | r | >20.0 | | S200115j_X136 | 2020-01-13 04:15:59 | 30 | r | >20.1 | | S200115j_X136 | 2020-01-13 04:43:21 | 30 | r | >19.5 | | S200115j_X136 | 2020-01-13 04:44:00 | 30 | r | >19.5 | | S200115j_X136 | 2020-01-13 05:28:55 | 30 | r | >19.4 | | S200115j_X136 | 2020-01-13 05:29:34 | 30 | r | >19.3 | | S200115j_X487 | 2020-01-13 04:43:21 | 30 | r | >19.5 | | S200115j_X487 | 2020-01-13 04:44:00 | 30 | r | >19.5 | | S200115j_X488 | 2020-01-13 04:43:21 | 30 | r | >19.6 | | S200115j_X488 | 2020-01-13 04:44:00 | 30 | r | >19.6 | | S200115j_X707 | 2020-01-15 06:28:56 | 300 | g | >21.0 | | S200115j_X707 | 2020-01-15 07:20:39 | 300 | g | >20.6 | | S200115j_X707 | 2020-01-18 05:40:26 | 300 | g | >21.4 | | S200115j_X717 | 2020-01-13 05:28:55 | 30 | r | >19.4 | | S200115j_X717 | 2020-01-13 05:29:34 | 30 | r | >19.4 | | S200115j_X745 | 2020-01-13 05:28:55 | 30 | r | >19.4 | | S200115j_X745 | 2020-01-13 05:29:34 | 30 | r | >19.4 | | S200115j_X746 | 2020-01-13 04:13:23 | 30 | r | >20.0 | | S200115j_X746 | 2020-01-13 04:14:02 | 30 | r | >19.9 | | S200115j_X746 | 2020-01-15 06:34:05 | 300 | g | >20.6 | | S200115j_X746 | 2020-01-18 05:45:35 | 300 | g | >21.2 | | S200115j_X748 | - | - | - | - | +---------------+---------------------+---------+--------+----------+ Evans et al. (GCN #26855) recommended the investigation of three sources in particular: S200115j_X136, S200115j_X707, and S200115j_X746. A discussion on S200115j_X136 is presented above. The coordinates of both S200115j_X707 and S200115j_X746 were observed with ZTF 2 days before S200115j, 2-3 hours after S200115j, and 3 days after S200115j. The non-detection of counterparts in ZTF data well constrains the presence of a bright optical transient evolving on hours to days timescales associated with S200115j_X707 or S200115j_X746. Further follow-up is encouraged. Forced photometry was performed on images processed through the ZTF reduction and image subtraction pipelines at IPAC (Masci et al. 2019). 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; IITB, India; IIA, India; LJMU, UK; TTU, USA; SDSU, 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.