TITLE: GCN CIRCULAR NUMBER: 27388 SUBJECT: LIGO/Virgo S200316bj: Identification of a GW compact binary merger candidate DATE: 20/03/16 22:28:06 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 S200316bj during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2020-03-16 21:57:56.157 UTC (GPS time: 1268431094.157). The candidate was found by the GstLAL [1], MBTAOnline [2], and SPIIR [3] analysis pipelines. S200316bj is an event of interest because its false alarm rate, as estimated by the online analysis, is 7.1e-11 Hz, or about one in 1e3 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S200316bj The classification of the GW signal, in order of descending probability, is MassGap (>99%), Terrestrial (<1%), BNS (<1%), BBH (<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 [4], distributed via GCN notice about 3 minutes after the candidate event time. * bayestar.fits.gz,1, an initial localization generated by BAYESTAR [4], distributed via GCN notice about 9 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 1117 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1222 +/- 340 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo Public Alerts User Guide . [1] Messick et al. PRD 95, 042001 (2017) [2] Adams et al. CQG 33, 175012 (2016) [3] Qi Chu, PhD Thesis, The University of Western Australia (2017) [4] Singer & Price PRD 93, 024013 (2016)