TITLE: GCN CIRCULAR NUMBER: 24570 SUBJECT: LIGO/Virgo S190517h: Identification of a GW compact binary merger candidate DATE: 19/05/17 06:45:54 GMT FROM: Shaon Ghosh at UWM The LIGO Scientific Collaboration and the Virgo Collaboration report: We identified the compact binary merger candidate S190517h during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-05-17 05:51:01.831 UTC (GPS time: 1242107479.831). The candidate was found by the GstLAL [1], CWB [2], MBTAOnline [3], PyCBC Live [4], and SPIIR [5] analysis pipelines. S190517h is an event of interest because its false alarm rate, as estimated by the online analysis, is 2.4e-09 Hz, or about one in 13 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S190517h The classification of the GW signal, in order of descending probability, is BBH (98%), MassGap (2%), NSBH (<1%), Terrestrial (<1%), or BNS (<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%). Using the masses and spins inferred from the signal, there is strong evidence against matter outside the final compact object (HasRemnant: <1%). One skymap is available at this time and can be retrieved from the GraceDB event page: * bayestar.fits.gz, an updated localization generated by BAYESTAR [6], distributed via GCN notice about 35 minutes after the candidate For the bayestar.fits.gz skymap, the 90% credible region is 939 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 2950 +/- 1038 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] Klimenko et al. PRD 93, 042004 (2016) [3] Adams et al. CQG 33, 175012 (2016) [4] Nitz et al. PRD 98, 024050 (2018) [5] Qi Chu, PhD Thesis, The University of Western Australia (2017) [6] Singer & Price PRD 93, 024013 (2016)