GCN Circular 24503

The LIGO Scientific Collaboration and the Virgo Collaboration report:

We identified the compact binary merger candidate S190512at during
real-time processing of data from LIGO Hanford Observatory (H1), LIGO
Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-05-12
18:07:14.422 UTC (GPS time: 1241719652.422). The candidate was found
by the PyCBC Live [1], CWB [2], GstLAL [3], MBTAOnline [4], and spiir
[5] analysis pipelines.

S190512at is an event of interest because its false alarm rate, as
estimated by the online analysis, is 1.9e-09 Hz, or about one in 16
years. The event's properties can be found at this URL:

https://gracedb.ligo.org/superevents/S190512at

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
[6], distributed via GCN notice about 53 minutes after the candidate.

For the bayestar.fits.gz skymap, the 90% credible region is 399 deg2.
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 1331 +/- 341 Mpc (a posteriori mean +/- standard
deviation).

No Preliminary Notice was sent for this event due to a technical problem.

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/><https://emfollow.docs.ligo.org/userguide/>.

[1] Nitz et al. PRD 98, 024050 (2018)
[2] Klimenko et al. PRD 93, 042004 (2016)
[3] Messick et al. PRD 95, 042001 (2017)
[4] Adams et al. CQG 33, 175012 (2016)
[5] Qi Chu, PhD Thesis, The University of Western Australia (2017)
[6] Singer & Price PRD 93, 024013 (2016)