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)