TITLE:   GCN CIRCULAR
NUMBER:  25826
SUBJECT: IceCube-190922B - HAWC follow-up
DATE:    19/09/23 22:09:37 GMT
FROM:    Antonio Galvan at Inst.de Astronomia,UNAM  <agalvan@astro.unam.mx>

On 2019-09-22 at  23:03:55.56 UTC, the IceCube collaboration detected a
track-like event with a moderate probability of being of astrophysical
origin, IceCube-190922B, at RA= 5.76  deg and Dec= -1.57 deg, J2000 (GCN
circular 25806). 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
2.74 x 1.86 degree rectangle around IceCube's reported location.

The highest significance, 0.63 sigma, was at RA= 6.37 deg, Dec= -1.49 deg
(J2000). Note that there are at least 5.5 trials in this search, so
post-trials significance is consistent with a non-detection. We set a
time-integrated upper limit 95% CL on the gamma-ray flux of E^2 dN/dE =
1.8e-13 (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. Looking in the same region of interest and spectrum we
obtain the following results:

Data acquisition on 2019-09-22 09:32:39 and ends 2019-09-23 09:28:43 (UTC),
1.16 sigma pre-trials (0.68 post trials), was at RA= 5.72 deg, Dec= -1.41
deg
(J2000). We set a time-integrated upper limit 95% CL on the gamma-ray flux
of: E^2 dN/dE = 1.5e-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.