TITLE: GCN CIRCULAR NUMBER: 31153 SUBJECT: IceCube-211125A: No significant detection in HAWC DATE: 21/11/30 16:21:39 GMT FROM: Hugo Ayala at Pennsylvania State University Hugo Ayala (Penn State) reports on behalf of the HAWC collaboration (http://www.hawc-observatory.org/collaboration): On 2021/11/25 06:22:21 UTC, the IceCube collaboration reported a track-like very-high-energy event that has a high probability of being an astrophysical neutrino, IceCube-211125A. Location is at RA: 43.59 (+3.13/-2.71 deg 90% PSF containment) J2000 Dec: 22.59 (+1.54/-2.53 deg 90% PSF containment) J2000 (GCN circular 31126). We performed two types of analyses for the follow-up. The first is for a steady source in archival data and the second is a search for a transient source. We assume a power-law spectrum with an index of -2.3 for both analyses. Search for a steady source in archival data: The archival data spans from November 2014 to June 2019. We searched inside the reported IceCube error region. The most significant location, with p-value 3.36e-3 (0.34 post-trials), is at RA 44.03 deg, Dec +20.62 deg (±0.10 deg 68% containment) J2000. We set a time-integrated 95% CL upper limit on gamma rays at the maximum position of: E^2 dN/dE = 2.66e-13 (E/TeV)^-0.3 TeV.cm^-2.s^-1 Search for a transient source. Since the IceCube event fall inside the HAWC field of view, we report on the result for the transit of the IceCube position. Data acquisition started on 2021/11/25 01:54:48 UTC and ended 2021/11/05 08:19:21 UTC. The most significant location, with p-value 3.8e-3 (0.34 post-trials), is at RA 43.07 deg, Dec +23.52 deg (±0.15 deg 68% containment) J2000. We set a time-integrated 95% CL upper limit at the position of maximum significance of: E^2 dN/dE = 1.36e-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.