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 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.