Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 26543

LIGO/Virgo S191222n: Identification of a GW compact binary merger candidate
2019-12-22T04:14:57Z (4 years ago)
Sarah Antier at APC <>
The LIGO Scientific Collaboration and the Virgo Collaboration report:

We identified the compact binary merger candidate S191222n during
real-time processing of data from LIGO Hanford Observatory (H1) and
LIGO Livingston Observatory (L1) at 2019-12-22 03:35:37.119 UTC (GPS
time: 1261020955.119). The candidate was found by the GstLAL [1],
SPIIR [2], and CWB [3] analysis pipelines.

S191222n is an event of interest because its false alarm rate, as
estimated by the online analysis, is 6.5e-12 Hz, or about one in 5e3
years. The event's properties can be found at this URL:

The classification of the GW signal, in order of descending
probability, is BBH (>99%), Terrestrial (<1%), 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
[4], distributed via GCN notice about 3 minutes after the candidate
event time.
 ��* bayestar.fits.gz,1, an initial localization generated by BAYESTAR
[4], distributed via GCN notice about 9 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 2324 deg2.
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 868 +/- 265 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] Qi Chu, PhD Thesis, The University of Western Australia (2017)
 ��[3] Klimenko et al. PRD 93, 042004 (2016)
 ��[4] Singer & Price PRD 93, 024013 (2016)
Looking for U.S. government information and services? Visit