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GCN Circular 27193

LIGO/Virgo S200225q: Identification of a GW compact binary merger candidate The LIGO Scientific Collaboration and the Virgo Collaboration
2020-02-25T06:38:12Z (4 years ago)
Vinaya Valsan at U. of Wisconsin Milwaukee <>
We identified the compact binary merger candidate S200225q during
real-time processing of data from LIGO Hanford Observatory (H1) and LIGO
Livingston Observatory (L1) at 2020-02-25 06:04:21.397 UTC (GPS time:
1266645879.397). The candidate was found by the PyCBC Live [1],
CWB [2], MBTAOnline [3], GstLAL [4], and SPIIR [5] analysis pipelines.

S200225q is an event of interest because its false alarm rate, as
estimated by the online analysis, is 9.2e-09 Hz, or about one in 3
years. The event's properties can be found at this URL:

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

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
[6], distributed via GCN notice about 3 minutes after the candidate
event time.
 * bayestar.fits.gz,1, an initial localization generated by BAYESTAR
[6], distributed via GCN notice about 11 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 668 deg2.
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 1234 +/- 341 Mpc (a posteriori mean +/- standard

For further information about analysis methodology and the contents of
this alert, refer to the LIGO/Virgo Public Alerts User Guide

 [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] Messick et al. PRD 95, 042001 (2017)
 [5] Qi Chu, PhD Thesis, The University of Western Australia (2017)
 [6] Singer & Price PRD 93, 024013 (2016)
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