//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27358 SUBJECT: LIGO/Virgo S200311bg: Identification of a GW compact binary merger candidate DATE: 20/03/11 12:28:04 GMT FROM: Geoffrey Mo at MIT The LIGO Scientific Collaboration and the Virgo Collaboration report: We identified the compact binary merger candidate S200311bg during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2020-03-11 11:58:53.398 UTC (GPS time: 1267963151.398). The candidate was found by the GstLAL [1], CWB [2], PyCBC Live [3], SPIIR [4], and MBTAOnline [5] analysis pipelines. S200311bg is an event of interest because its false alarm rate, as estimated by the online analysis, is 8.9e-26 Hz, or about one in 1e18 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S200311bg The classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), BNS (<1%), MassGap (<1%), or NSBH (<1%). Assuming the candidate is astrophysical in origin, the probability that the lighter compact object has a mass < 3 solar masses (HasNS) is <1%. Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. Two 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 [6], distributed via GCN notice about 2 minutes after the candidate event time. * bayestar.fits.gz,1, an initial localization generated by BAYESTAR [6], distributed via GCN notice about 10 minutes after the candidate event time. The preferred sky map at this time is bayestar.fits.gz,1. For the bayestar.fits.gz,1 sky map, the 90% credible region is well fit by an ellipse with an area of 52 deg2 described by the following DS9 region (right ascension, declination, semi-major axis, semi-minor axis, position angle of the semi-minor axis): icrs; ellipse(00h08m, -07d27m, 8.54d, 1.98d, 72.86d) Marginalized over the whole sky, the a posteriori luminosity distance estimate is 924 +/- 188 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] Klimenko et al. PRD 93, 042004 (2016) [3] Nitz et al. PRD 98, 024050 (2018) [4] Qi Chu, PhD Thesis, The University of Western Australia (2017) [5] Adams et al. CQG 33, 175012 (2016) [6] Singer & Price PRD 93, 024013 (2016) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27359 SUBJECT: LIGO/Virgo S200311bg: Upper limits from IceCube neutrino searches DATE: 20/03/11 12:28:49 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 S200311bg in a time range of 1000 seconds [3] centered on the alert event time (2020-03-11 11:50:33.398 UTC to 2020-03-11 12:07:13.398 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 S200311bg 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 S200311bg ranges from 0.029 to 0.194 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: 27360 SUBJECT: LIGO/Virgo S200311bg: No counterpart candidates in INTEGRAL SPI-ACS,prompt observation DATE: 20/03/11 13:06:08 GMT FROM: Carlo Ferrigno at IAAT/ISDC C. Ferrigno, V. Savchenko (ISDC/UniGE, Switzerland) J. Rodi (IAPS-Roma, Italy) A. Coleiro (APC, France) S. Mereghetti (INAF IASF-Milano, Italy) on behalf of the INTEGRAL multi-messenger collaboration: https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration Using INTEGRAL/SPI-ACS realtime data (following [1]) we have performed a search for a prompt gamma-ray counterpart of S200311bg (GCN 27358). At the time of the event (2020-03-11 11:58:53 UTC, hereafter T0), INTEGRAL was operating in nominal mode. The peak of the event localization probability was at an angle of 90 deg with respect to the spacecraft pointing axis, near the direction of the Sun. This orientation implies strongly suppressed (6% of optimal) response of ISGRI, strongly suppressed (29% of optimal) response of IBIS/Veto, and strongly suppressed (34% of optimal) response of SPI-ACS. The background within +/-300 seconds around the event was very stable (excess variance 1.1). We have performed a search for any impulsive events in INTEGRAL SPI- ACS (as described in [2]) data. We do not detect any significant counterparts and estimate a 3-sigma upper limit on the 75-2000 keV fluence of 4.5e-07 erg/cm^2 (within the 50% probability containment region of the source localization) 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 ~4.7e-07 (1.4e-07) erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range. For the mean reported distance 924.0 Mpc this corresponds to the limit on the total isotropic equivalent energy in 1 s of 4.6e+49 erg for the short GRB spectrum and for a long GRB spectrum isotropic equivalent luminosity in 1 s (8 s) of 4e+49 erg/s (1.5e+49 erg/s) We report for completeness and in order of FAP, all excesses identified in the search region. We find: 5 likely background excesses: T-T0 | scale | S/N | luminosity ( x 1e+49 erg/s) | FAP 5.44 | 0.45 | 3.2 | 7.71 +/- 2.48 +/- 2.65 | 0.161 134 | 2.25 | 3.6 | 3.71 +/- 1.1 +/- 1.28 | 0.382 28.8 | 1 | 3 | 4.72 +/- 1.66 +/- 1.62 | 0.633 159 | 2.1 | 3.4 | 3.74 +/- 1.14 +/- 1.28 | 0.7 110 | 0.45 | 3.9 | 9.35 +/- 2.48 +/- 3.21 | 0.875 Note that FAP estimates (especially at timescales above 2s) may be possibly further affected by enhanced non-stationary local background noise. This list excludes any excesses for which FAP is close to unity. All result s quoted are preliminary. This circular is an official product of the INTEGRAL Multi-Messenger team. [1] Savchenko et al. 2017, A&A 603, A46 [2] Savchenko et al. 2012, A&A 541A, 122S //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27361 SUBJECT: LIGO/Virgo S200311bg: not observable by AGILE at the event time DATE: 20/03/11 14:11:32 GMT FROM: Francesco Longo at U of Trieste,INFN Trieste F. Longo (Univ. Trieste, and INFN Trieste) M. Pilia (INAF/OA-Cagliari), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), C.Casentini, M.Cardillo, G. Piano, A.Ursi (INAF/IAPS), F.Lucarelli, C. Pittori, F. Verrecchia (SSDC, and INAF/OAR), A. Bulgarelli, V. Fioretti, N. Parmiggiani (INAF/OAS-Bologna) report on behalf of the AGILE Team: In response to the LIGO/Virgo GW event S200311bg at T0 = 2020-03-11 11:58:53.398 (UTC), a preliminary analysis of the AGILE MCAL and GRID data found no acquisitions around T0, due to a complete Earth occultation of the S200311bg 90% c.l. localization region. Additional analysis of AGILE data is in progress. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27362 SUBJECT: LIGO/Virgo S200311bg: Coverage and upper limits from MAXI/GSC observations DATE: 20/03/11 14:36:20 GMT FROM: Satoshi Sugita at Aoyama Gakuin U. S. Sugita, M. Serino (AGU), N. Kawai (Tokyo Tech), H. Negoro (Nihon U.), 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 S200311bg at 2020-03-11 11:58:53.398 UTC (GCN 27358). At the trigger time of S200311bg, the high-voltage of MAXI/GSC was off, and it was turned on at T0+1163 sec (+19.4 min). The first one-orbit (92 min) scan observation with GSC after the event covered 81% of the 90% credible region of the bayestar skymap from 12:18:16 to 12:20:08 UTC (T0+1163 to T0+1275 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: 27364 SUBJECT: LIGO/Virgo S200311bg: not observable by Fermi GBM DATE: 20/03/11 16:58:22 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 group: At the time of S200311bg, Fermi was passing through the South Atlantic Anomaly from 2.9 minutes prior to 24.6 minutes after the trigger time; therefore the GBM detectors were disabled. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27368 SUBJECT: LIGO/Virgo S200311bg: No significant counterpart candidates in Fermi-LAT observations DATE: 20/03/11 23:40:36 GMT FROM: Masanori Ohno at Hiroshima University M. Kovacevic (INFN Perugia), M. Ohno (Hiroshima University), M. Axelsson (KTH & Stockholm Univ), E. Bissaldi (Politecnico & INFN Bari), D. Kocevski (NASA/MSFC), N. Omodei (Stanford Univ.), N. Di Lalla (Stanford Univ.) and F. Longo (University and INFN, Trieste) report on behalf of the Fermi-LAT Collaboration: We have searched data collected by the Fermi Large Area Telescope (LAT) on March 11, 2020, for possible high-energy (E > 100 MeV) gamma-ray emission in spatial/temporal coincidence with the LIGO/Virgo trigger S200311bg (GCN 27358). 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. The Fermi Gamma-ray Space Telescope was passing through the South Atlantic Anomaly (SAA) at the time of the trigger (T0 = 2020-03-11 11:58:53.398 UTC). During SAA passages both the LAT and the Gamma-ray Burst Monitor (GBM) do not collect data due to the high charged particle background in this region. The LAT resumed taking data upon exiting the SAA at roughly T0 + 1.6 ks. At that time the instantaneous coverage was 100% of the LIGO probability map, therefore 100% cumulative coverage was reached at that time as well. 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 + 1.6 ks 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 8.0e-10 and 1.1e-8 [erg/cm^2/s]. The Fermi-LAT point of contact for this event is Milos Kovacevic (milos.kovacevic@pg.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: 27369 SUBJECT: LIGO/Virgo S200311bg: Swift/BAT in the South Atlantic Anomaly DATE: 20/03/12 00:33:07 GMT FROM: Amy Lien at GSFC S. D. Barthelmy (NASA/GSFC), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), T. Sakamoto (AGU), 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: Around the trigger time (T0) of LIGO/Virgo S200311bg (LIGO/VIRGO Collaboration GCN Circ. 27358), Swift/BAT was in the South Atlantic Anomaly (SAA) until T0+60 s. Therefore, no science data were collected during this time. The results of the BAT analysis are available at https://swift.gsfc.nasa.gov/results/BATbursts/team_web/S200311bg/web/source_public.html //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27372 SUBJECT: LIGO/Virgo S200311bg: Not observable by CALET DATE: 20/03/12 12:18:33 GMT FROM: Yuta Kawakubo at Louisiana State U./CALET S. Torii (Waseda U), A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), Y. Asaoka (Waseda U), Y. Shimizu, 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 S200311bg, T0 = 2020-03-11 11:58:53.398 UT (The LIGO Scientific Collaboration and Virgo Collaboration, GCN Circ. 27358), the CALET Gamma-ray Burst Monitor (CGBM) high voltages were off (from T0-3 min to T0+15 min). The CALET Calorimeter (CAL) was operating in the high energy trigger mode at the trigger time of S200311bg. 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. There was no significant overlap with the LVC high probability localization region at T0+-60 sec. The CAL FOV was centered at RA = 191.3 deg, Dec = +51.5 deg at T0. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27382 SUBJECT: LIGO/Virgo S200311bg: Updated Sky Localization and EM Bright Classification DATE: 20/03/13 15:12:55 GMT FROM: Geoffrey Mo at MIT 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 S200311bg (GCN Circular 27358). 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/S200311bg 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 well fit by an ellipse with an area of 34 deg2 described by the following DS9 region (right ascension, declination, semi-major axis, semi-minor axis, position angle of the semi-minor axis): icrs; ellipse(00h09m, -08d14m, 6.91d, 1.59d, 72.77d) Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1115 +/- 175 Mpc (a posteriori mean +/- standard deviation). Based on posterior support from parameter estimation [1], under the assumption that the candidate S200311bg is astrophysical in origin, the probability that the lighter compact object has a mass < 3 solar masses (HasNS) is <1%. Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo Public Alerts User Guide . [1] Veitch et al. PRD 91, 042003 (2015) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 27487 SUBJECT: LIGO/Virgo S200311bg: Upper limits from Konus-Wind observations DATE: 20/04/03 22:20:06 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 S200311bg (2020-03-11 11:58:53.398 UTC, hereafter T0; LIGO/Virgo Collaboration GCN Circ. 27358). No triggered KW GRBs happened between ~3 hours before and ~1.5 days 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 8.2x10^-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 2.4x10^-7 erg/cm^2/s (20 - 1500 keV, 2.944 s scale). All the quoted values are preliminary.