GCN Circular 21693

The LIGO Scientific Collaboration and Virgo report:


The MBTA CBC analysis (Adams et al. CQG 33, 175012, 2016) identified
candidate G299232 during real-time processing of data from LIGO
Hanford Observatory (H1) and LIGO Livingston Observatory (L1) at
2017-08-25 13:13:31 UTC (GPS time: 1187702035.9831). Data from Virgo
(V1) were included in a followup analysis using the PyCBC toolkit
(Nitz, et al. 2017, arXiv:1705.01513
Not found
 
 
) and used to generate the
localization given below.

G299232 is a low-significance CBC candidate with a false alarm rate,
As determined by the online analysis, of 1.68e-07 Hz, or about 5.3 per
year, just within our threshold of 6 per year for announcing
candidates. The event's properties can be found at this URL:

https://gracedb.ligo.org/events/view/G299232

If the candidate is astrophysical in origin, it appears consistent
with the merger of a black hole and a neutron star. For more details
on the source classification, please consult this technical document:

https://dcc.ligo.org/T1600571/public/main<https://owa.exchange.mit.edu/owa/redir.aspx?C=08JG3EzySZbccUYOg_q0nFAJYtskviWom-7tvEUl40pBz1r9vuvUCA..&URL=https%3a%2f%2fdcc.ligo.org%2fT1600571%2fpublic%2fmain>

A rapid localization with distance information generated by the
BAYESTAR pipeline (Singer et al. 2016, ApJL 829, 15) including
information from H1, L1, and V1 is available and can be retrieved from
the GraceDB event page: bayestar-HLV.fits.gz.

The 50% credible region spans about 450 deg2 and the 90% region about
2040 deg2. The probability is concentrated in a pair of long, thin
arcs that spread across both the northern and southern hemispheres,
although the probability is concentrated in the northern
hemisphere. Marginalized over the whole sky, the a posteriori
luminosity distance estimate is 339 +/-110 Mpc.

Updates on our analysis of this event, including updated localizations
will be sent as they become available.