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GCN Circular 20763

Subject
LIGO/Virgo G275697: Identification of a GW CBC Candidate
Date
2017-02-27T19:51:32Z (7 years ago)
From
Karelle Siellez at Georgia Inst of Tech <karelle.siellez@ligo.org>
The LIGO Scientific Collaboration and Virgo report:

The pycbc CBC analysis (Usman et al. 2016, CQG 33, 215004) identified
candidate G275697 during real-time processing of data from LIGO
Hanford Observatory (H1) and LIGO Livingston Observatory (L1) at
2017-02-27 18:57:31.375 UTC (GPS time: 1172257069.375).

G275697 is an event of interest because its false alarm rate, as
determined by the online analysis, is 1.43e-07 Hz or about one in 2
months, passing our alert threshold of ~1/month. The event's
properties can be found at this URL:

https://gracedb.ligo.org/events/G275697

No other GW event candidates were identified within a 300 s window
before or after G275697.

Based on preliminary matched-filter estimates of the masses and spins,
if astrophysical, there is a 100% chance that the less massive companion
in the binary has a mass less than 3 Msun. Based on the tidal disruption
condition and disk mass formula of Foucart (PRD 86, 124007), using an
implementation based on Pannarale & Ohme (ApJL 791, 7), we estimate
that there is a 100% chance that the system ejected enough neutron-rich
material to power an electromagnetic transient.

One sky map with directional distance information (e.g., Singer et al.
2016, ApJL 829, 15) is available at this time and can be retrieved from
the GraceDB event page: bayestar.fits.gz, an initial localization generated
by the BAYESTAR pipeline. The probability is concentrated in two
sections of an annulus. The 50% credible region spans about 480 deg2 and
the 90% region about 1800 deg2. The luminosity distance is estimated to
be 181 +/- 55 Mpc (mean +/- standard deviation). This is the preferred sky
map at this time.

Updates on our analysis of this event will be sent as they become
available.
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