The LIGO Scientific Collaboration and the Virgo Collaboration report:
We identified the compact binary merger candidate S190828j during
real-time processing of data from LIGO Hanford Observatory (H1), LIGO
Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-08-28
06:34:05.756 UTC (GPS time: 1251009263.756). The candidate was found
by the GstLAL , CWB , PyCBC Live , MBTAOnline , and SPIIR
 analysis pipelines.
S190828j is an event of interest because its false alarm rate, as
estimated by the online analysis, is 8.5e-22 Hz, or about one in 1e14
years. The event's properties can be found at this URL:
The classification of the GW signal, in order of descending
probability, is BBH (>99%), Terrestrial (<1%), BNS (<1%), MassGap
(<1%), or NSBH (<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 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
, distributed via GCN notice about 16 minutes after the candidate
For the bayestar.fits.gz sky map, the 90% credible region is 603 deg2.
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 2276 +/- 538 Mpc (a posteriori mean +/- standard
For further information about analysis methodology and the contents of
this alert, refer to the LIGO/Virgo Public Alerts User Guide
 Messick et al. PRD 95, 042001 (2017)
 Klimenko et al. PRD 93, 042004 (2016)
 Nitz et al. PRD 98, 024050 (2018)
 Adams et al. CQG 33, 175012 (2016)
 Qi Chu, PhD Thesis, The University of Western Australia (2017)
 Singer & Price PRD 93, 024013 (2016)