[vsnet-grb-info 24915] LIGO/Virgo S200208q: Identification of a GW compact binary merger candidate

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27014
SUBJECT: LIGO/Virgo S200208q: Identification of a GW compact binary merger candidate
DATE:    20/02/08 13:35:30 GMT
FROM:    Leo Singer at GSFC  <leo.p.singer at nasa.gov>

The LIGO Scientific Collaboration and the Virgo Collaboration report:

We identified the compact binary merger candidate S200208q during
real-time processing of data from LIGO Hanford Observatory (H1), LIGO
Livingston Observatory (L1), and Virgo Observatory (V1) at 2020-02-08
13:01:17.991 UTC (GPS time: 1265202095.991). The candidate was found
by the MBTAOnline [1], CWB [2], PyCBC Live [3], and SPIIR [4] analysis
pipelines.

S200208q is an event of interest because its false alarm rate, as
estimated by the online analysis, is 2.5e-09 Hz, or about one in 12
years. The event's properties can be found at this URL:
https://gracedb.ligo.org/superevents/S200208q

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, the probability
that the lighter compact object has a mass < 3 solar masses (HasNS) is
<1%. Using the masses and spins inferred from the signal, the
probability of matter outside the final compact object (HasRemnant) is
<1%.

Two sky maps are available at this time and can be retrieved from the
GraceDB event page:
 * bayestar.fits.gz,0, an initial localization generated by BAYESTAR
[5], distributed via GCN notice about 3 minutes after the candidate
event time.
 * bayestar.fits.gz,1, an initial localization generated by BAYESTAR
[5], distributed via GCN notice about 9 minutes after the candidate
event time.

The preferred sky map at this time is bayestar.fits.gz,1. For the
bayestar.fits.gz,1 sky map, the 90% credible region is 1120 deg2.
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 2900 +/- 960 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] Adams et al. CQG 33, 175012 (2016)
 [2] Klimenko et al. PRD 93, 042004 (2016)
 [3] Nitz et al. PRD 98, 024050 (2018)
 [4] Qi Chu, PhD Thesis, The University of Western Australia (2017)
 [5] Singer & Price PRD 93, 024013 (2016)