[vsnet-grb-info 23139] IceCube-190730A - HAWC follow-up

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25238
SUBJECT: IceCube-190730A - HAWC follow-up
DATE:    19/07/31 21:11:35 GMT
FROM:    Antonio Galvan at Inst.de Astronomia,UNAM  <agalvan at astro.unam.mx>

Antonio Galvan (IA-UNAM), Israel Martinez-Castellanos (UMD) and Jose Andres
Garcia-Gonzalez (IF-UNAM) reports on behalf of the HAWC collaboration (
http://www.hawc-observatory.org/collaboration/):

On 2019-07-30 at 20:50:41.31 UTC, the IceCube collaboration reported a
track-like event with a moderate probability of being of astrophysical
origin, IceCube-190730A, at RA= 225.79 deg and Dec= +10.47 deg, J2000 (GCN
circular 25225). In HAWC's sky, the neutrino was at zenith of 60.74  deg
and 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
1.43 x 1.14 degree rectangle around IceCube's reported location.

The highest significance, 2.38 sigma, was at RA= 226.54 deg, Dec= 10.35 deg
(J2000). Note that there are at least 27 trials in this search, so
post-trials significance is lower and equal to 0.712. We set a
time-integrated upper limit 95% CL on the gamma-ray flux of E^2 dN/dE =
2.418e-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. The results are the following:

1.) 2019-07-29
Transit starts on 2019-07-29 22:00:36 and ends 2019-07-30 04:06:48 (UTC),
0.75 sigma pre-trials (0 post trials), was at RA= 225.64 deg, Dec= 9.86 deg
(J2000). We set a time-integrated upper limit 95% CL on the gamma-ray flux
of: E^2 dN/dE = 1.013e-11 (E/TeV)^-0.3 TeV cm^-2 s^-1.

2.) 2019-07-30
Transit starts on 2019-07-30 21:56:40 and ends 2019-07-31 04:02:52  (UTC),
1.76 sigma pre-trials (0 post trials), was at RA= 225.51 deg, Dec= 10.73
deg (J2000). We set a time-integrated upper limit 95% CL on the gamma-ray
flux of: E^2 dN/dE = 1.251e-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.