TITLE: GCN CIRCULAR NUMBER: 25087 SUBJECT: LIGO/Virgo S190718y: Identification of a GW compact binary merger candidate DATE: 19/07/18 16:07:48 GMT FROM: Varun Bhalerao at Indian Inst of Tech The LIGO Scientific Collaboration and the Virgo Collaboration report: We identified the compact binary merger candidate S190718y during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-07-18 14:35:12.068 UTC (GPS time: 1247495730.068). The candidate was found by the GstLAL [1] analysis pipeline. S190718y is an event of interest because its false alarm rate, as estimated by the online analysis, is 3.6e-08 Hz, or about one in 10 months. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S190718y There were glitches in the interferometers tens of seconds before merger which may affect the sky maps. Further analysis is underway. The classification of the GW signal, in order of descending probability, is Terrestrial (98%), BNS (2%), NSBH (<1%), BBH (<1%), or MassGap (<1%). Assuming the candidate is astrophysical in origin, there is strong evidence for the lighter compact object having a mass < 3 solar masses (HasNS: >99%). Using the masses and spins inferred from the signal, there is strong evidence for matter outside the final compact object (HasRemnant: >99%). One sky map is available at this time and can be retrieved from the GraceDB event page: * bayestar.fits.gz, an updated localization generated by BAYESTAR [2], distributed via GCN notice about 27 minutes after the candidate For the bayestar.fits.gz sky map, the 90% credible region is 7246 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 227 +/- 165 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] Singer & Price PRD 93, 024013 (2016)