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

GCN Circular 25087

LIGO/Virgo S190718y: Identification of a GW compact binary merger candidate
2019-07-18T16:07:48Z (5 years ago)
Varun Bhalerao at Indian Inst of Tech <>
The LIGO Scientific Collaboration and the Virgo Collaboration report:

We identified the compact binary merger candidate S190718y during
real-time processing of data from LIGO Hanford Observatory (H1), LIGO
Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-07-18
14:35:12.068 UTC (GPS time: 1247495730.068). The candidate was found
by the GstLAL [1] analysis pipeline.

S190718y is an event of interest because its false alarm rate, as
estimated by the online analysis, is 3.6e-08 Hz, or about one in 10
months. The event's properties can be found at this URL:

There were glitches in the interferometers tens of seconds before 
merger which may affect the sky maps. Further analysis is underway.

The classification of the GW signal, in order of descending
probability, is Terrestrial (98%), BNS (2%), NSBH (<1%), BBH (<1%), or
MassGap (<1%).

Assuming the candidate is astrophysical in origin, there is strong
evidence for the lighter compact object having a mass < 3 solar masses
(HasNS: >99%). Using the masses and spins inferred from the signal,
there is strong evidence for matter outside the final compact object
(HasRemnant: >99%).

One sky map is available at this time and can be retrieved from the
GraceDB event page:
 * bayestar.fits.gz, an updated localization generated by BAYESTAR
[2], distributed via GCN notice about 27 minutes after the candidate

For the bayestar.fits.gz sky map, the 90% credible region is 7246
deg2. Marginalized over the whole sky, the a posteriori luminosity
distance estimate is 227 +/- 165 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)
Looking for U.S. government information and services? Visit