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GCN Circular 27278

LIGO/Virgo S200302c: Identification of a GW compact binary merger candidate
2020-03-02T02:20:13Z (4 years ago)
Peter Shawhan at U of Maryland/LSC <>
The LIGO Scientific Collaboration and the Virgo Collaboration report:

We identified the compact binary merger candidate S200302c during
real-time processing of data from LIGO Hanford Observatory
(H1) and Virgo Observatory (V1) at 2020-03-02 01:58:11.519 UTC (GPS
time: 1267149509.519). The candidate was found by the GstLAL [1]
analysis pipeline.

S200302c is an event of interest because its false alarm rate, as
estimated by the online analysis, is 9.3e-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 (89%), Terrestrial (11%), BNS (<1%), MassGap
(<1%), or NSBH (<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
[2], distributed via GCN notice about a minute after the candidate
event time.
 * bayestar.fits.gz,1, distributed via GCN notice about 7 minutes after
the candidate event time.  (This is identical to bayestar.fits.gz,0 )

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 6704 deg2.
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 1737 +/- 500 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] Messick et al. PRD 95, 042001 (2017)
[2] Singer & Price PRD 93, 024013 (2016)
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