{
  "bibcode": "2019GCN.25503....1L",
  "body": "The LIGO Scientific Collaboration and the Virgo Collaboration report:\n\n\nWe identified the compact binary merger candidate S190828l during\nreal-time processing of data from LIGO Hanford Observatory (H1), LIGO\nLivingston Observatory (L1), and Virgo Observatory (V1) at 2019-08-28\n06:55:09.887 UTC (GPS time: 1251010527.887). The candidate was found\nby the GstLAL [1], MBTAOnline [2], SPIIR [3], and PyCBC Live [4]\nanalysis pipelines.\n\nNote that S190828l and S190828j (GCN 25497) are distinct events that\noccurred 21 minutes apart.\n\nS190828l is an event of interest because its false alarm rate, as\nestimated by the online analysis, is 4.6e-11 Hz, or about one in 700\nyears. The event's properties can be found at this URL:\n\nhttps://gracedb.ligo.org/superevents/S190828l\n\nThe classification of the GW signal, in order of descending\nprobability, is BBH (>99%), Terrestrial (<1%), BNS (<1%), MassGap\n(<1%), or NSBH (<1%).\n\nAssuming the candidate is astrophysical in origin, there is strong\nevidence against the lighter compact object having a mass < 3 solar\nmasses (HasNS: <1%). Using the masses and spins inferred from the\nsignal, there is strong evidence against matter outside the final\ncompact object (HasRemnant: <1%).\n\nOne sky map is available at this time and can be retrieved from the\nGraceDB event page:\n * bayestar.fits.gz, an updated localization generated by BAYESTAR\n[5], distributed via GCN notice about 22 minutes after the candidate\n\nFor the bayestar.fits.gz sky map, the 90% credible region is 948 deg2.\nMarginalized over the whole sky, the a posteriori luminosity distance\nestimate is 1609 +/- 426 Mpc (a posteriori mean +/- standard\ndeviation).\n\nThe localizations of S190828j and S190828l strongly resemble each\nother. This is not unexpected for events occurring at similar times\nbecause the detector sensitivity antenna patterns rotate with the\nEarth. The two localizations are definitely disjoint: their\nprevailing triangulation annuli are separated by over 10 degrees.\n\nFor further information about analysis methodology and the contents of\nthis alert, refer to the LIGO/Virgo Public Alerts User Guide\n<https://emfollow.docs.ligo.org/userguide/>.\n\n [1] Messick et al. PRD 95, 042001 (2017)\n [2] Adams et al. CQG 33, 175012 (2016)\n [3] Qi Chu, PhD Thesis, The University of Western Australia (2017)\n [4] Nitz et al. PRD 98, 024050 (2018)\n [5] Singer & Price PRD 93, 024013 (2016)",
  "circularId": 25503,
  "createdOn": 1566982249000,
  "email": "qi.chu@ligo.org",
  "subject": "LIGO/Virgo S190828l: Identification of a GW compact binary merger candidate",
  "submitter": "Qi Chu at LSC  <qi.chu@ligo.org>",
  "eventId": "LIGO/Virgo S190828l"
}