TITLE:   GCN CIRCULAR
NUMBER:  24598
SUBJECT: LIGO/Virgo S190519bj: Identification of a GW compact binary merger candidate
DATE:    19/05/19 17:09:42 GMT
FROM:    Roberto De Pietri at LIGO/Virgo  <roberto.depietri@unipr.it>

The LIGO Scientific Collaboration and the Virgo Collaboration report:

We identified the compact binary merger candidate S190519bj during
real-time processing of data from LIGO Hanford Observatory (H1), LIGO
Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-05-19
15:35:44.398 UTC (GPS time: 1242315362.398). The candidate was found
by the PyCBC Live [1], CWB [2], GstLAL [3], MBTAOnline [4], and SPIIR
[5] analysis pipelines.

S190519bj is an event of interest because its false alarm rate, as
determined by the online analysis, is 5.7e-09 Hz, or about one in 5
years. The event's properties can be found at this URL:

https://gracedb.ligo.org/superevents/S190519bj

The classification of the GW signal, in order of descending
probability, is BBH (96%), Terrestrial (4%), BNS (<1%), NSBH (<1%),
or MassGap (<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 skymap is available at this time and can be retrieved from the
GraceDB event page:
 * bayestar.fits.gz, an updated localization generated by BAYESTAR
[6], distributed via GCN notice about 59 minutes after the candidate

For the bayestar.fits.gz skymap, the 90% credible region is 967 deg2.
Marginalized over the whole sky, the a posteriori luminosity distance
estimate is 3154 +/- 791 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] 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)


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