[vsnet-grb-info 25031] LIGO/Virgo S200219ac: Identification of a GW compact binary merger candidate

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  27130
SUBJECT: LIGO/Virgo S200219ac: Identification of a GW compact binary merger candidate
DATE:    20/02/19 12:53:35 GMT
FROM:    Sarah Antier at APC  <antier at apc.in2p3.fr>

The LIGO Scientific Collaboration and the Virgo Collaboration report:

We identified the compact binary merger candidate S200219ac during
real-time processing of data from LIGO Hanford Observatory (H1), LIGO
Livingston Observatory (L1), and Virgo Observatory (V1) at 2020-02-19
09:44:15.195 UTC (GPS time: 1266140673.195). The candidate was found
by the PyCBC Live [1], CWB [2], MBTAOnline [3], SPIIR [4], and GstLAL [5]
analysis pipelines.

The delay in issuing the alert was due to a software issue in the
online system.

S200219ac is an event of interest because its false alarm rate, as
estimated by the online analysis, is 1.3e-08 Hz, or about one in 2
years. The event's properties can be found at this URL:
https://gracedb.ligo.org/superevents/S200219ac

The classification of the GW signal, in order of descending
probability, is BBH (96%), Terrestrial (4%), 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%.

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
[6], distributed via GCN notice about 2 hours after the candidate.

The preferred sky map at this time is bayestar.fits.gz. For the
bayestar.fits.gz sky map, the 90% credible region is 1251 deg2.
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 1510 +/- 405 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] Nitz et al. PRD 98, 024050 (2018)
  [2] Klimenko et al. PRD 93, 042004 (2016)
  [3] Adams et al. CQG 33, 175012 (2016)
  [4] Qi Chu, PhD Thesis, The University of Western Australia (2017)
  [5] Messick et al. PRD 95, 042001 (2017)
  [6] Singer & Price PRD 93, 024013 (2016)