//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31106 SUBJECT: Alert from the HAWC Burst Monitor HAWC-211123A DATE: 21/11/23 15:11:08 GMT FROM: Hugo Ayala at Pennsylvania State University The HAWC Collaboration (http://www.hawc-observatory.org/collaboration/) reports: On 11 23, 2021, at 03:52:23.50 UTC, HAWC detected a burst signal from its Burst Monitoring named HAWC-211123A. 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 1-second time window starting at the reported trigger time. The position of the alert is RA (J200): 34.12 deg Dec (J2000): -8.05 deg Location uncertainty (68% containment): 0.60 deg (statistical only). The monitor system found that this alert has a false alarm rate of 1.92 alert(s) per year. We encourage follow-up observations of the HAWC alert region. We however note that it is consistent with background expectations based on the observation time. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31111 SUBJECT: HAWC-211123A: No neutrino counterpart detected with ANTARES DATE: 21/11/24 09:21:21 GMT FROM: Antoine Kouchner at ANTARES Collaboration Alexis Coleiro (APC/Universite 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-211123A alert (event 110400_42 ). 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 88% of time in the up-going field of view of ANTARES. At T0, the elevation of the alert was -7.3 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 17 GeV.cm^-2 over the energy range 3 TeV – 3 PeV (the range corresponding to 5-95% of the detectable flux) for an E^-2 power-law spectrum, and about 70 GeV.cm^-2 (0.5 - 280 TeV) for an E^-2.5 spectrum. A search over an extended time window of +/-1 day has also yielded no detection (54% 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. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31114 SUBJECT: HAWC-211123A: not observable by Fermi-GBM DATE: 21/11/24 18:41:14 GMT FROM: Cori Fletcher at USRA C. Fletcher (USRA) reports on behalf of the Fermi-GBM team: At the time of the burst candidate HAWC-211123A (GCN 31106), Fermi was passing through the South Atlantic Anomaly from 3.0 minutes prior until 18.6 minutes after the trigger time; therefore the GBM detectors were disabled. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31115 SUBJECT: HAWC-211123A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation DATE: 21/11/24 19:22:25 GMT FROM: Volodymyr Savchenko at ISDC,U of Geneve V. Savchenko, C. Ferrigno (ISDC/UniGE, Switzerland) J. Rodi (IAPS-Roma, Italy) A. Coleiro (APC, France) S. Mereghetti (INAF IASF-Milano, Italy) on behalf of the INTEGRAL multi-messenger collaboration: https://www.astro.unige.ch/cdci/integral-multimessenger-collaboration Using combination of INTEGRAL all-sky detectors (following [1]): SPI/ACS, IBIS/Veto, and IBIS we have performed a search for a prompt gamma-ray counterpart of HAWC-211123A (GCN 31106). At the time of the event (2021-11-23 03:52:23 UTC, hereafter T0), INTEGRAL was operating in nominal mode. The peak of the event localization probability was at an angle of 86 deg with respect to the spacecraft pointing axis. This orientation implies strongly suppressed (15% of optimal) response of ISGRI, strongly suppressed (30% of optimal) response of IBIS/Veto, and somewhat suppressed (66% of optimal) response of SPI-ACS. The background within +/-300 seconds around the event was rather stable (excess variance 1.3). We have performed a search for any impulsive events in INTEGRAL SPI- ACS (as described in [2]), IBIS, and IBIS/Veto data. We do not detect any significant counterparts and estimate a 3-sigma upper limit on the 75-2000 keV fluence of 2.6e-07 erg/cm^2 (within the 50% probability containment region of the source localization) for a burst lasting less than 1 s with a characteristic short GRB spectrum (an exponentially cut off power law with alpha=-0.5 and Ep=600 keV) occurring at any time in the interval within 300 s around T0. For a typical long GRB spectrum (Band function with alpha=-1, beta=-2.5, and Ep=300 keV), the derived peak flux upper limit is ~2.2e-07 (7.7e-08) erg/cm^2/s at 1 s (8 s) time scale in 75-2000 keV energy range. We report for completeness and in order of FAP, all excesses identified in the search region. We find: 2 possibly associated excesses: T-T0 | scale | S/N | flux ( x 1e-06 erg/cm2/s) | FAP -4.74 | 2.1 | 3.2 | 1.9 +/- 0.57 +/- 0.576 | 0.0349 13.1 | 1.1 | 4 | 3.25 +/- 0.79 +/- 0.987 | 0.0388 6 likely background excesses: T-T0 | scale | S/N | flux ( x 1e-06 erg/cm2/s) | FAP -42.6 | 1.4 | 3.9 | 2.83 +/- 0.7 +/- 0.859 | 0.111 18.8 | 0.95 | 3.1 | 2.78 +/- 0.849 +/- 0.844 | 0.377 -120 | 3.3 | 3.2 | 1.47 +/- 0.455 +/- 0.445 | 0.59 -95.4 | 0.85 | 3.5 | 3.31 +/- 0.899 +/- 1 | 0.787 -35.1 | 0.05 | 4.4 | 1.7 +/- 0.38 +/- 0.516 | 0.806 164 | 0.55 | 4.1 | 0.475 +/- 0.112 +/- 0.144 | 0.831 Note that FAP estimates (especially at timescales above 2s) may be possibly further affected by enhanced non-stationary local background noise. This list excludes any excesses for which FAP is close to unity. All results quoted are preliminary. This circular is an official product of the INTEGRAL Multi-Messenger team. [1] Savchenko et al. 2017, A&A 603, A46 [2] Savchenko et al. 2012, A&A 541A, 122S GCN pipeline version: 62a8c26