TITLE: GCN CIRCULAR NUMBER: 25296 SUBJECT: LIGO/Virgo S190808ae: Identification of a GW compact binary merger candidate DATE: 19/08/08 23:18:23 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 S190808ae during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-08-08 22:21:21.496 UTC (GPS time: 1249338099.496). The candidate was found by the GstLAL [1] analysis pipeline. S190808ae is an event of interest because its false alarm rate, as estimated by the online analysis, is 3.4e-08 Hz, or about one in 11 months. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S190808ae The classification of the GW signal, in order of descending probability, is Terrestrial (57%), BNS (43%), BBH (<1%), MassGap (<1%), or NSBH (<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 6 minutes after the candidate For the bayestar.fits.gz sky map, the 90% credible region is 5365 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 208 +/- 77 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)