//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29958 SUBJECT: Alert from the HAWC Burst Monitor HAWC-210507A DATE: 21/05/07 15:56:02 GMT FROM: Hugo Ayala at Pennsylvania State University The HAWC Collaboration (http://www.hawc-observatory.org/collaboration/) reports: On May 07, 2021, at 10:38:22 UT, HAWC detected a burst signal from its Burst Monitoring named HAWC-210507A. This monitor system looks for excesses above the expected background in time windows of 0.2, 1, 10 and 100 seconds. This event was found in the 10-second time window starting at the reported trigger time. The position of the alert is RA (J200): 257.24 deg Dec (J2000): 8.08 deg Location uncertainty (68% containment): 0.4 deg (statistical only). The monitor system found that this alert has a false alarm rate of 3.76 alert(s) per year. We encourage follow-up observations of the HAWC alert region. We however note that it is consistent with background expectation based on the observation time. The initial automated alert is recorded here: https://gcn.gsfc.nasa.gov/notices_amon_hawc/1010067_1345.amon 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. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29967 SUBJECT: HAWC-210507A: No neutrino counterpart candidates in ANTARES search DATE: 21/05/08 16:13:42 GMT FROM: Antoine Kouchner at ANTARES Collaboration Alexis Coleiro (APC/Univ de Paris) and Damien Dornic (CPPM/CNRS) on behalf of the ANTARES Collaboration. Using data from the ANTARES detector, we have performed a follow-up analysis of the recently reported HAWC-210507A alert (event 1010067_1345 ). No up-going muon neutrino candidate events were detected within the error box of the HAWC event during a +/- 1h time-window centered on the HAWC event time (T0), and over which the potential source remained visible all time in the up-going field of view of ANTARES. At T0, the elevation of the alert was -24 degrees below the horizon for ANTARES. This leads to a preliminary 90% confidence level upper limit on the muon-neutrino radiant fluence from a point source of about 15 GeV.cm^-2 over the energy range 4 TeV – 4 PeV (the range corresponding to 5-95% of the detectable flux) for an E^-2 power-law spectrum, and about 37 GeV.cm^-2 (0.7 - 380 TeV) for an E^-2.5 spectrum. A search over an extended time window of +/-1 day has also yielded no detection (45% visibility). ANTARES is the largest undersea neutrino detector (Mediterranean Sea) and it is primarily sensitive to astrophysical neutrinos in the TeV-PeV energy range. At 10 TeV, the median angular resolution for muon neutrinos is about 0.5 degrees. In the range 1-100 TeV ANTARES has a competitive sensitivity to this position in the sky.