TITLE: GCN CIRCULAR NUMBER: 24098 SUBJECT: LIGO/Virgo S190412m: Identification of a GW binary merger candidate DATE: 19/04/12 07:28:32 GMT FROM: Peter Shawhan at U of Maryland/LSC The LIGO Scientific Collaboration and the Virgo Collaboration report: We identified the compact binary merger candidate S190412m during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-04-12 05:30:44.166 UTC (GPS time: 1239082262.166). The candidate was found by the GstLAL [1], SPIIR [2], CWB [3], MBTAOnline [4], and PyCBC Live [5] analysis pipelines. S190412m is a candidate of interest because its false alarm rate, as determined by the online analysis, is estimated to be 1.7e-27 Hz. The candidate's properties can be found at this URL: https://gracedb.ligo.org/superevents/S190412m The initial classification of the signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), BNS (<1%), NSBH (<1%), or MassGap (<1%). Assuming the candidate is astrophysical in origin, there is strong evidence against the lighter compact object having a mass < 3 solar masses (HasNS: <1%). The current estimate of the probability of nonzero remnant mass outside the final BH horizon (HasRemnant) reported in the GCN Notice is not reliable. One skymap is available at this time and can be retrieved from the GraceDB candidate page: * bayestar.fits.gz, a preliminary localization generated by BAYESTAR [6], distributed via GCN notice about an hour after the time of the candidate (delayed by a technical issue). For the bayestar.fits.gz skymap, the 90% credible region is 156 deg2. Marginalized over the whole sky, the luminosity distance estimate is 812 +/- 194 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] Qi Chu, PhD Thesis, University of Western Australia (2017) [3] Klimenko et al. PRD 93, 042004 (2016) [4] Adams et al. CQG 33, 175012 (2016) [5] Nitz et al. PRD 98, 024050 (2018) [6] Singer & Price PRD 93, 024013 (2016)