GCN Circular 25411

Antonio Galvan (IA-UNAM), Israel Martinez-Castellanos (UMD) report on
behalf of the HAWC collaboration
(http://www.hawc-observatory.org/collaboration/):

On August 19, 2019 at 17:34:24.24, the IceCube collaboration reported
a track-like very-high-energy event that has a high probability of
being an astrophysical neutrino, IceCube-190819A, at RA = 148.80 deg
and Dec = 1.38 deg, J2000 (GCN circular 25402
Not found
 
 
). In HAWC's sky, the
neutrino was at zenith of 23.00 deg and setting. 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 spectral index of -2.3 we searched in a 9.29

degree square around IceCube's reported location. The highest

significance, 2.68 sigma, was at RA = 148.36 deg, Dec = 1.60 deg

(J2000). Note that there are at least 46 trials in this search, so the

post-trials significance is 0.96. We set a time-integrated upper limit
95% CL on gamma rays of:

E^2 dN/dE = 3.20643e-13 (E/TeV)^-0.3 TeV cm^-2 s^-1.


* Search for a transient source.

We integrated from 19:00 UTC to 21:22 UTC. Due to maintaince, we did
not collect data during the period 15:42 UTC to 19:00 UTC,during which
the IceCube location would had been otherwise observable by HAWC.

For this observed period,the most significant location,

within the 9.29 degree square,is 2.29 sigma (RA = 148.37 deg, Dec =
1.70 deg, J2000)  with a post-trials significance of 0.027.

We set a time-integrated upper limit 95% CL on gamma rays of:

E^2 dN/dE = 2.3535e-11 (E/TeV)^-0.3 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.