GCN Circular 28709
The HAWC Collaboration (http://www.hawc-observatory.org/collaboration/) reports: On 2020-10-19, at 21:43:42 UT, HAWC detected a burst signal from its Burst Monitoring named HAWC-201019A. 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 100-second time window starting at the reported trigger time. The position of the alert is RA (J200): 203.148 deg Dec (J2000): 29.717 deg Location uncertainty (68% containment): 0.6 deg (statistical only). The monitor system found that this alert has a false alarm rate of 2.37 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/gcn/notices_amon_hawc/1009678_72.amon We note that a quick search on the FAVA monitoring (https://fermi.gsfc.nasa.gov/ssc/data/access/lat/FAVA/), an old alert, FAVA_223_2, is 0.29 deg away from HAWC-201019A, which occurred on 2012-11-05 15:43:35. See: https://fermi.gsfc.nasa.gov/ssc/data/access/lat/FAVA/LightCurve.php?ra=203.148&dec=29.717 The source 4FGL J1330.7+2933 is located 0.43 deg away from HAWC-201019A and is also positionally consistent with the FAVA event. 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.