TITLE:   GCN CIRCULAR
NUMBER:  20486
SUBJECT: LIGO/Virgo G270580: Identification of a GW Burst Candidate
DATE:    17/01/20 14:38:03 GMT
FROM:    Gergely Dalya at Eotvos U  <dalyag@caesar.elte.hu>

The LIGO Scientific Collaboration and Virgo report:

The online CWB Burst analysis identified a candidate with GraceDB ID
G270580 during processing of data from LIGO Hanford Observatory (H1)
and LIGO Livingston Observatory (L1) at 2017-01-20 12:30:59.350 UTC
(GPS time: 1168950677.350).

G270580 is an event of interest because its false alarm rate, as
determined by preliminary analysis, is 1.6e-07 Hz (about one in 2.4
months). The event's properties can be found at this URL:

https://gracedb.ligo.org/events/G270580

This event candidate does *not* have a chirp signature, and thus does
not suggest a compact binary merger. The initial GCN Notice for this
candidate (ivorn=ivo://nasa.gsfc.gcn/LVC#G270580-6-Initial)
erroneously included "ProbHasNS" and "ProbHasRemnant" values due to a
software bug; we regret any confusion that may have caused. (These
probabilities are only calculated for CBC event candidates.)

Two sky maps have been calculated and can be retrieved from the
GraceDB event page. LIB_skymap.fits.gz, a rapid localization using
LALInference (Veitch et al., PRD 91, 042003) for Burst reconstruction,
is the preferred sky map at this time. The 50% credible region spans
about 600 deg2 and the 90% region about 3100 deg2. The CWB skymap has
a consistent shape but is broader.

We will provide updated information about this event candidate as it
becomes available.