GCN Circular 24098

The LIGO Scientific Collaboration and the Virgo Collaboration report:

We identified the compact binary merger candidate S190412m during
real-time processing of data from LIGO Hanford Observatory (H1), LIGO
Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-04-12
05:30:44.166 UTC (GPS time: 1239082262.166). The candidate was found by
the GstLAL [1], SPIIR [2], CWB [3], MBTAOnline [4], and PyCBC Live [5]
analysis pipelines.

S190412m is a candidate of interest because its false alarm rate, as
determined by the online analysis, is estimated to be 1.7e-27 Hz. The
candidate's properties can be found at this URL:

https://gracedb.ligo.org/superevents/S190412m

The initial classification of the 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%). The current estimate of the probability of nonzero remnant
mass outside the final BH horizon (HasRemnant) reported in the GCN Notice
is not reliable.

One skymap is available at this time and can be retrieved from the GraceDB
candidate page:
 * bayestar.fits.gz, a preliminary localization generated by BAYESTAR [6],
   distributed via GCN notice about an hour after the time of the
   candidate (delayed by a technical issue).

For the bayestar.fits.gz skymap, the 90% credible region is 156 deg2.
Marginalized over the whole sky, the luminosity distance estimate is
812 +/- 194 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] Qi Chu, PhD Thesis, University of Western Australia (2017)
 [3] Klimenko et al. PRD 93, 042004 (2016)
 [4] Adams et al. CQG 33, 175012 (2016)
 [5] Nitz et al. PRD 98, 024050 (2018)
 [6] Singer & Price PRD 93, 024013 (2016)