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GCN Circular 26454

LIGO/Virgo S191216ap: Identification of a GW compact binary merger candidate
2019-12-16T22:03:55Z (4 years ago)
Brandon Piotrzkowski at U of Wisconsin-Milwaukee <>
The LIGO Scientific Collaboration and the Virgo Collaboration report:

We identified the compact binary merger candidate S191216ap during
real-time processing of data from LIGO Hanford Observatory (H1) and
Virgo Observatory (V1) at 2019-12-16 21:33:38.473 UTC (GPS time:
1260567236.473). The candidate was found by the GstLAL [1], MBTAOnline
[2], and PyCBC Live [3] analysis pipelines.

S191216ap is an event of interest because its false alarm rate, as
estimated by the online analysis, is 1.1e-23 Hz, or about one in 1e15
years. The event's properties can be found at this URL:

The classification of the GW signal, in order of descending
probability, is MassGap (>99%), Terrestrial (<1%), BNS (<1%), BBH
(<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
19%. Using the masses and spins inferred from the signal, the
probability of matter outside the final compact object (HasRemnant) is

One sky map is available at this time and can be retrieved from the
GraceDB event page:
 * bayestar.fits.gz,0, an initial localization generated by BAYESTAR
[4], distributed via GCN notice about 16 minutes after the candidate
event time.

For the bayestar.fits.gz,0 sky map, the 90% credible region is 300
deg2. Marginalized over the whole sky, the a posteriori luminosity
distance estimate is 324 +/- 78 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] Adams et al. CQG 33, 175012 (2016)
 [3] Nitz et al. PRD 98, 024050 (2018)
 [4] Singer & Price PRD 93, 024013 (2016)
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