[vsnet-grb-info 25976] Update of alert from the HAWC Burst Monitor HAWC-200709A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  28076
SUBJECT: Update of alert from the HAWC Burst Monitor HAWC-200709A
DATE:    20/07/10 22:38:42 GMT
FROM:    Hugo Ayala at Pennsylvania State University  <hgayala at psu.edu>

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

On July 9th, 2020, at 04:47:11 UT, HAWC detected a burst signal
from its Burst Monitoring named HAWC-200709A. This monitor system looks
for excesses above the expected background in time windows of 0.2, 1, 10
and 100 seconds.
This event was found in the 100-second time window starting
at the reported trigger time.

We apply an offline analysis around the time and location of the
HAWC-200709A alert.
The offline analysis consists of a maximum likelihood analysis where
we compare the presence of a source against the background-only hypothesis.
We use the search window where the alert was detected for the analysis.

The results of the offline analysis are:
RA (J200): 252.60 deg
Dec (J2000): 15.48 deg
Location uncertainty (68% containment): 0.39 deg (statistical only).
FAR: 16.04 per year

This result just confirms the previous sub-threshold alert from the
real-time system
with an update on the position.

The initial automated alert is recorded here:
https://gcn.gsfc.nasa.gov/notices_amon_hawc/1009500_793.amon

HAWC is a very-high-energy gamma-ray observatory operating in Central
Mexico at latitude 19 deg. north. Operating day and night with over
95% duty cycle, HAWC has an instantaneous field of view of 2 sr and
surveys 2/3 of the sky every day. It is sensitive to gamma rays
from 300 GeV to 100 TeV.