[vsnet-grb-info 22138] LIGO/Virgo S190426c: Identification of a GW compact binary merger candidate

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  24237
SUBJECT: LIGO/Virgo S190426c: Identification of a GW compact binary merger candidate
DATE:    19/04/26 16:45:04 GMT
FROM:    Deep Chatterjee at University of Wisconsin,Milwaukee  <deep at uwm.edu>

The LIGO Scientific Collaboration and the Virgo Collaboration report:


We identified the compact binary merger candidate S190426c during

real-time processing of data from LIGO Hanford Observatory (H1), LIGO

Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-04-26

15:21:55.337 UTC (GPS time: 1240327333.337). The candidate was found

by the GstLAL [1], MBTAOnline [2], PyCBC Live [3], and SPIIR [4]

analysis pipelines.


S190426c is an event of interest because its false alarm rate, as

estimated by the online analysis, is 1.9e-08 Hz, or about one in 1

year, 7 months. The event's properties can be found at this URL:


https://gracedb.ligo.org/superevents/S190426c


The classification of the GW signal, in order of descending

probability, is BNS (49%), MassGap (24%), Terrestrial (14%), NSBH

(13%), or BBH (<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%).


Two skymaps are available at this time and can be retrieved from the

GraceDB event page:

* bayestar.fits.gz, the preliminary sky localization generated by

  BAYESTAR [5], distributed via GCN notice about 25 minutes after

  the candidate,

* bayestar1.fits.gz, an updated localization distributed via GCN

  notice about an hour after the candidate. This is the preferred

  skymap at this time.


For the bayestar1.fits.gz skymap, the 90% credible region is 1262

deg2. Marginalized over the whole sky, the a posteriori luminosity

distance estimate is 375 +/- 108 Mpc (a posteriori mean +/- standard

deviation).


For further information about analysis methodology and the contents of

this alert, refer to the LIGO/Virgo Public Alerts User Guide

<https://emfollow.docs.ligo.org/userguide/><https://emfollow.docs.ligo.org/userguide/>.


[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] Qi Chu, PhD Thesis, The University of Western Australia (2017)

[5] Singer & Price PRD 93, 024013 (2016)