GCN Circular 24522

The LIGO Scientific Collaboration and the Virgo Collaboration report:

We identified the compact binary merger candidate S190513bm during
real-time processing of data from LIGO Hanford Observatory (H1), LIGO
Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-05-13
20:54:28.747 UTC (GPS time: 1241816086.747). The candidate was found
by the GstLAL [1], CWB [2], MBTAOnline [3], and spiir [4] analysis
pipelines.

S190513bm is an event of interest because its false alarm rate, as
estimated by the online analysis, is 3.7e-13 Hz, or about one in 1e5
years. The event's properties can be found at this URL:

https://gracedb.ligo.org/superevents/S190513bm

The classification of the GW signal, in order of descending
probability, is BBH (94%), MassGap (5%), 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

[5], distributed via GCN notice about 27 minutes after the candidate

For the bayestar.fits.gz skymap, the 90% credible region is 691 deg2.
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 1987 +/- 501 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
<https://emfollow.docs.ligo.org/userguide/>.

[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] Qi Chu, PhD Thesis, The University of Western Australia (2017)
[5] Singer & Price PRD 93, 024013 (2016)