//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31514 SUBJECT: Fermi-LAT-ANTARES 220121a Coincidence DATE: 22/01/21 16:44:54 GMT FROM: Timothee Gregoire at Penn State ANTARES 220121A: AMON + ANTARES Identification of a Low False-Alarm Rate High-Energy Neutrino + Fermi LAT Coincidence C. F. Turley, D. B. Fox and T. Gregoire (for AMON https://www.amon.psu.edu/) + M. Ageron (CNRS/CPPM), A. Coleiro (Univ. de Paris/APC), D. Dornic (CNRS/CPPM), A. Kouchner (Univ. de Paris/APC) (for ANTARES) report: During operations of the AMON ANTARES neutrino + Fermi LAT gamma-ray multimessenger alerts, at 21 January 2022 at 01:02:01 UT, we identified a low false alarm-rate (1.497 per year) coincidence between one ANTARES neutrino and one Fermi LAT photon. An alert was automatically generated and, after human review, distributed to AMON partner facilities and here publicly. Alert details are as follows:     Date:  21 January 2022     Time:  01:02:01 UT     R.A.:  300.984 (J2000)     Dec.:  -69.3334 (J2000)     r_90:  0.109 deg (90%-containment)     FAR:   1.497 yr-1 ANTARES 220121A is a high-energy neutrino-induced muon event detected by ANTARES (Ageron et al. 2011) with coordinates R.A. 307.21, Dec. -67.163 (J2000) at 01:02:32 UT, and a p-value based on the number of hits used for the reconstruction of 0.7853, which relates to the deposited energy. The minimum false alarm rate coincidence from our analysis associates this neutrino with one Fermi LAT photon. The photon was detected at 01:01:30 UT with coordinates R.A. 301, Dec. -69.3347 (J2000) and energy 16.0 GeV.  The best-fit localization and uncertainty for a point source yielding the ANTARES 220121A neutrino and the photon is as quoted above. The false alarm rate for ANTARES neutrino + Fermi LAT gamma-ray coincidences of this quality or better is 1 per 0.668 years. There is no know GeV emitter (based on the Fermi-LAT 4FGL catalog) in the vicinity of the found coincidence. The nearest one is 4FGL J1956.6-7011 (with is 1.06deg away). Details of the ANTARES + Fermi LAT coincidence search procedures are provided in Ayala Solares et al. 2019 (ApJ 886, 98). False alarm rates are established from 73,000 years of simulated observation and take into account the point spread functions of the associated neutrino + photons, the known backgrounds at this sky position, the energy of the neutrino, and the energies of the Fermi LAT photons (within broad ranges). We provide the associated AMON alert for this coincidence in GCN Alert format, below. ////////////////////////////////////////////////////////////////////// TITLE: GCN/AMON NOTICE NOTICE_DATE: Fri 21 Jan 2022 09:02:09 UT NOTICE_TYPE: Fermi-LAT ANTARES coincidence AMON_NUM: 1475022503 SRC_RA: 300.984d {+20h03m56.3s} (J2000),         301.493d {+20h05m58.2s} (current),         299.705d {+19h58m49.1s} (1950) SRC_DEC: -69.3334d {-4h37m20.0s} (J2000),          -69.2756d {-4h37m06.2s} (current),          -69.474d {-4h37m53.8s} (1950) SRC_ERROR90: 0.109 [deg, stat, 90% containment] DISCOVERY_DATE: 19600 TJD;  021 DOY; 22/01/21 (yy/mm/dd) DISCOVERY_TIME: 3721 SOD {1:02:01.400} UT REVISION: 0 DELTA_T: 61.20 [sec] SIGMA_T: 30.60 [sec] FAR: 1.497 [yr^-1] SUN_POSTN: 302.851d {+20h11m24s} -20.0102d {-20d00m37s} SUN_DIST: 49.34 [deg] Sun_angle= 12.0584 [hr] MOON_POSTN: 159.214d {+10h36m51s} 14.1667d {+14d10m00s} MOON_DIST: 119.85 [deg] GAL_COORDS: 326.13, -31.6249 [deg] galactic lon,lat of the event COMMENTS: ALERT FROM FERMI-LAT ANTARES COINCIDENCE STREAM //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 31516 SUBJECT: Fermi-LAT-ANTARES 220121a: upper limits from a search for coincident neutrinos with IceCube DATE: 22/01/21 21:07:12 GMT FROM: Alex Pizzuto at ICECUBE/U of Wisconsin The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search for track-like muon neutrino events arriving from the best-fit localization region of the recent coincidence between one ANTARES neutrino and one Fermi LAT photon (https://gcn.gsfc.nasa.gov/gcn3/31514.gcn3). The search was performed using a time window one day in duration centered on the alert time (2022-01-20 13:02:01 UTC to 2022-01-21 13:02:01 UTC), during which IceCube was collecting good quality data. We find that the data are consistent with atmospheric background expectations, with a p-value of 1. We accordingly derive a time-integrated muon-neutrino flux upper limit for this source of E^2 dN/ dE = 9.3 x 10^-4 TeV cm^-2 at 90% CL, under the assumption of an E^-2 power law. 90% of events IceCube would detect from a source at this declination with an E^-2 spectrum have energies in the approximate energy range between 100 TeV and 20 PeV. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc@icecube.wisc.edu.