The LIGO Scientific Collaboration and the Virgo Collaboration report:
We identified the compact binary merger candidate S190521r during
real-time processing of data from LIGO Hanford Observatory (H1) and
LIGO Livingston Observatory (L1) at 2019-05-21 07:43:59.463 UTC (GPS
time: 1242459857.463). The candidate was found by the PyCBC Live ,
SPIIR , CWB , and GstLAL  analysis pipelines.
S190521r is an event of interest because its false alarm rate, as
determined by the online analysis, is 3.2e-10 Hz, or about one in 100
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%), NSBH (<1%),
or MassGap (<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
, distributed via GCN notice about 6 minutes after the candidate
For the bayestar.fits.gz skymap, the 90% credible region is 488 deg2.
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 1136 +/- 279 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
 Nitz et al. PRD 98, 024050 (2018)
 Qi Chu, PhD Thesis, The University of Western Australia (2017)
 Klimenko et al. PRD 93, 042004 (2016)
 Messick et al. PRD 95, 042001 (2017)
 Singer & Price PRD 93, 024013 (2016)