[vsnet-grb-info 23654] LIGO/Virgo S190915ak: Identification of a GW compact binary merger candidate

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25753
SUBJECT: LIGO/Virgo S190915ak: Identification of a GW compact binary merger candidate
DATE:    19/09/16 00:27:49 GMT
FROM:    Alan Weinstein at Caltech/LIGO  <ajw at caltech.edu>

The LIGO Scientific Collaboration and the Virgo Collaboration report:

We identified the compact binary merger candidate S190915ak during

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

Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-09-15

23:57:02.691 UTC (GPS time: 1252627040.691). The candidate was found

by the GstLAL [1], SPIIR [2], CWB [3], and MBTAOnline [4] analysis

pipelines.

S190915ak is an event of interest because its false alarm rate, as

estimated by the online analysis, is 9.7e-10 Hz, or about one in 32

years. The event's properties can be found at this URL:

https://gracedb.ligo.org/superevents/S190915ak

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, there is strong

evidence against the lighter compact object having a mass < 3 solar

masses (HasNS: <1%). Using the masses and spins inferred from the

signal, there is strong evidence against matter outside the final

compact object (HasRemnant: <1%).

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

[5], distributed via GCN notice about 6 minutes after the candidate

For the bayestar.fits.gz sky map, the 90% credible region is 528 deg2.

Marginalized over the whole sky, the a posteriori luminosity distance

estimate is 1557 +/- 381 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/>.

 [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] Adams et al. CQG 33, 175012 (2016)

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