TITLE:   GCN CIRCULAR
NUMBER:  26472
SUBJECT: LIGO/Virgo S191216ap: HAWC gamma-ray sub-threshold event coincident with LIGO/Virgo and IceCube localizations
DATE:    19/12/17 13:54:23 GMT
FROM:    Israel Martinez-Castellanos at UMD/HAWC  <imc@umd.edu>

The HAWC Collaboration (https://www.hawc-observatory.org) reports:

The HAWC Collaboration performed a follow-up of the gravitational wave
trigger S191216ap, reported in GCN Circular 26455. We did not report
a significant detection after considering the trials incurred by
looking at the whole gravitational wave localization contour.

We however found that the most significant sub-threshold event is
coincident with the (corrected) localization of a neutrino event
reported by IceCube in GCN Circular 26463 (RA: 323.19 deg,
Dec: 4.53 deg, 90% cont.: 4.07 deg). The HAWC event coordinates are:

RA (J2000):   323.53 deg
Dec (J2000):  5.23 deg
68% cont.:    0.30 deg
Significance: 4.6 sigma (pre-trials)

This event was found in the 10 s search, starting at 1260567316.47 GPSs
(80.0 s after the time of coalescence).

We encourage follow-up observations of this location.