GCN Circular 25324

The LIGO Scientific Collaboration and the Virgo Collaboration report:

We identified the compact binary merger candidate S190814bv during
real-time processing of data from LIGO Hanford Observatory (H1), LIGO
Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-08-14
21:10:39.013 UTC (GPS time: 1249852257.013).
The candidate was found by the GstLAL [1], pycbc [2],
MBTAOnline [3], and CWB [4] analysis pipelines.

S190814bv is an event of interest because its false alarm rate, as
estimated by the online analysis, is 2e-33 Hz, or about one in 1e25
years. The event's properties can be found at this URL:

https://gracedb.ligo.org/superevents/S190814bv

The classification of the GW signal, in order of descending
probability, is MassGap (>99%), Terrestrial (<1%), BNS (<1%), BBH
(<1%), or NSBH (<1%). These values are based on
point mass estimates which assigns an estimate of 100% to a single
astrophysical class when the Terrestrial probability is very small.
We will provide updates based on parameter estimation as soon
as they become available.

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%).

Two sky maps are available at this time and can be retrieved from the
GraceDB event page:
 * a sky map generated by BAYESTAR [5] using data from the
   Livingston and Virgo detectors, distributed via GCN notice about
   21 minutes after the candidate.
 * bayestar.fits.gz, an updated sky map generated by BAYESTAR using
   data from the Livingston, Hanford, and Virgo detectors, distributed
   about 2 hours after the candidate. This is the preferred skymap.
   The 90% credible region is 38 deg2. Marginalized over the whole sky,
   the a posteriori luminosity distance estimate is 276 +/- 56 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] Nitz et al. PRD 98, 024050 (2018)
 [3] Adams et al. CQG 33, 175012 (2016)
 [4] Klimenko et al. PRD 93, 042004 (2016)
 [5] Singer & Price PRD 93, 024013 (2016)