[vsnet-grb-info 23706] IceCube-190922A - HAWC follow-up

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25805
SUBJECT: IceCube-190922A - HAWC follow-up
DATE:    19/09/23 01:29:35 GMT
FROM:    Antonio Galvan at Inst.de Astronomia,UNAM  <agalvan at astro.unam.mx>

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

On 2019-09-22 at 09:42:45.62 UTC, the IceCube collaboration detected a
track-like event with a moderate probability of being of astrophysical
origin, IceCube-190922A, at RA= 167.43 deg and Dec= -22.39 deg, J2000 (GCN
circular 25802). In HAWC's sky, the neutrino was outside of our field of
view.
We have performed a search in our archival data 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
6.8 x 5.78 degree rectangle around IceCube's reported location.

The highest significance, 1.31 sigma, was at RA= 168.35 deg, Dec= -23.81 deg
(J2000). Note that there are at least 196.5 trials in this search, so
post-trials significance is consistent with 0. We set a
time-integrated upper limit 95% CL on the gamma-ray flux of E^2 dN/dE =
1.2e-12 (E/TeV)^-0.3 TeV cm^-2 s^-1.

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

Data acquisition on 2019-09-21 16:27:31 and ends 2019-09-22 18:45:53 (UTC),
1.32 sigma pre-trials (0 post trials), was at RA= 166.14 deg, Dec= -23.01
deg
(J2000). We set a time-integrated upper limit 95% CL on the gamma-ray flux
of: E^2 dN/dE = 6.1e-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.