GCN Circular 24996

Antonio Galv��n (IA-UNAM), Jos�� Andr��s Garc��a-Gonz��lez (IF-UNAM) and Israel
Martinez-Castellanos(UMD) reports on behalf of the HAWC collaboration (
http://www.hawc-observatory.org/collaboration/):


On 2019-07-04 at 18:48:52.25 UTC, the IceCube collaboration reported a
track-like event with a moderate probability of being of astrophysical
origin, IceCube-190704A, at RA 161.85 deg and Dec 27.11 deg, J2000 (GCN
circular 24981
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 ). In HAWC's sky, the neutrino was at zenith of 50.62  deg
and outside of our field of view. We have searched for a steady source as
well as a transient source.

* Search for a steady source in archival data from November 2014 to May
2018. Assuming a  power law with a spectral index of -2.3 we searched in a
4.08 degree circle around IceCube's reported location.

The highest significance, 2.75 sigma, was at RA= 162.47 deg, Dec= 26.28 deg
(J2000). Note that there are at least 250 trials in this search, so
post-trials significance is lower and equal to 0.65. We set a
time-integrated upper limit 95% CL on gamma rays of E^2 dN/dE = 2.52e-13
(E/TeV)^-2.3 TeV cm^-2 s^-1

* Search for a transient source: Since the events was not in our filed of
view at the time reported on the GCN we did a search for the day before as
well. The results are the following:

1.) 2019-07-03
Transit starts on 2019-07-03 19:17:59 and ends 2019-07-04 01:44:07 (UTC)

The highest significance, 4.06 sigma pre-trials (2.45 post trials), was at
RA= 161.67 deg, Dec= 26.80 deg (J2000). We set a time-integrated upper
limit 95% CL on gamma rays of: E^2 dN/dE = 1.98e-11 (E/TeV)^-2.3 TeV cm^-2
s^-1

2.) 2019-07-04
Transit starts on 2019-07-04 19:14:03 and ends 2019-07-05 01:40:11  (UTC)

The highest significance, 2.56 sigma pre-trials (zero post trials), was at
RA= 160.09 deg, Dec= 27.80 deg (J2000). We set a time-integrated upper
limit 95% CL on gamma rays of: E^2 dN/dE = 1.11e-11 (E/TeV)^-2.3 TeV cm^-2
s^-1


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.