TITLE: GCN CIRCULAR NUMBER: 20250 SUBJECT: HAWC follow-up on IceCube-161210 DATE: 16/12/13 18:15:22 GMT FROM: Israel Martinez at HAWC Israel Martinez (University of Maryland) reports on behalf of the HAWC collaboration (http://www.hawc-observatory.org/collaboration/): On 2016/12/10 20:07:16 UT IceCube detected a track-like, very-high-energy event with a high probability of being of astrophysical origin, at RA=46.58d and Dec=14.98d J2000. It was reported in GCN circular 20247. Two analyses were performed: * Search for a steady source. This analysis was performed on archival data from November 2014 to June 2016. Assuming a spectral index of -2.3 we searched in a rectangular window corresponding to IceCube's 90% PSF containment for the event (1.72deg^2). The maximum significance is 2.83 sigma at RA=47.46d and Dec=14.59d. We estimate the number of trials to be ~70. We set an upper limit 95% CL on gamma rays for this period of: E^2 dN/dE = 3.23e-13 (E/TeV)^-0.3 TeV cm^-2 s^-1. * Search for a transient source. The event location was not in HAWC's FOV at the time of detection, so this analysis was performed using data corresponding to the two nearest 6hrs transits (MJD 57732.05-57732.30 and 57733.05-57733.30). Using the same spectral index and search window, the maximum significance is 1.71 sigma at RA=46.57d and Dec=15.18d. We set an upper limit 95% CL on gamma rays for this period of: E^2 dN/dE = 1.54e-11 (E/TeV)^-0.3 TeV cm^-2 s^-1. HAWC is a very-high-energy gamma-ray observatory located in Central Mexico at latitude 19 deg North. It operates 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.