Skip to main content
Introducing Einstein Probe, Astro Flavored Markdown, and Notices Schema v4.0.0. See news and announcements

GCN Circular 27184

LIGO/Virgo S200224ca: Identification of a GW compact binary merger candidate The LIGO Scientific Collaboration and the Virgo Collaboration
2020-02-24T22:53:00Z (4 years ago)
Vinaya Valsan at U. of Wisconsin Milwaukee <>
We identified the compact binary merger candidate S200224ca during
real-time processing of data from LIGO Hanford Observatory (H1),LIGO
Livingston Observatory (L1), and Virgo Observatory (V1) at 2020-02-24
22:22:34.406 UTC (GPS time: 1266618172.406). The candidate was found
by the PyCBC Live [1], CWB [2], GstLAL [3], MBTAOnline [4] ,and SPIIR [5]
analysis pipelines.

S200224ca is an event of interest because its false alarm rate, as
estimated by the online analysis, is 1.6e-11 Hz, or about one in 1e3
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%), 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 10 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 well fit by an
ellipse with an area of 73 deg2 described by the following DS9 region
(right ascension, declination, semi-major axis, semi-minor axis,
position angle of the semi-minor axis):
   icrs; ellipse(11h38m42s, -09d20m21s, 9d, 3d, 68d)
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 1585 +/- 331 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] Messick et al. PRD 95, 042001 (2017)
 [4] Adams et al. CQG 33, 175012 (2016)
 [5] Qi Chu, PhD Thesis, The University of Western Australia (2017)
 [6] Singer & Price PRD 93, 024013 (2016) [7] Singer & Price PRD 93,
024013 (2016)
Looking for U.S. government information and services? Visit