GCN Circular 25296

The LIGO Scientific Collaboration and the Virgo Collaboration report:


We identified the compact binary merger candidate S190808ae during
real-time processing of data from LIGO Hanford Observatory (H1), LIGO
Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-08-08
22:21:21.496 UTC (GPS time: 1249338099.496). The candidate was found
by the GstLAL [1] analysis pipeline.

S190808ae is an event of interest because its false alarm rate, as
estimated by the online analysis, is 3.4e-08 Hz, or about one in 11
months. The event's properties can be found at this URL:

https://gracedb.ligo.org/superevents/S190808ae

The classification of the GW signal, in order of descending
probability, is Terrestrial (57%), BNS (43%), BBH (<1%), MassGap
(<1%), or NSBH (<1%).

Assuming the candidate is astrophysical in origin, there is strong
evidence for the lighter compact object having a mass < 3 solar masses
(HasNS: >99%). Using the masses and spins inferred from the signal,
there is strong evidence for matter outside the final compact object
(HasRemnant: >99%).

One sky map is available at this time and can be retrieved from the
GraceDB event page:
 ��* bayestar.fits.gz, an updated localization generated by BAYESTAR
[2], distributed via GCN notice about 6 minutes after the candidate

For the bayestar.fits.gz sky map, the 90% credible region is 5365
deg2. Marginalized over the whole sky, the a posteriori luminosity
distance estimate is 208 +/- 77 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] Singer & Price PRD 93, 024013 (2016)