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GCN Circular 28063

Fermi-LAT-ANTARES 200407a Coincidence
2020-07-05T17:37:13Z (4 years ago)
Colin F Turley at AMON, Penn State U <>
AMON + ANTARES Identification of a Low False-Alarm
Rate High-Energy Neutrino + Fermi LAT Coincidence

C. F. Turley and D. B. Fox (for AMON +
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 + Fermi LAT neutrino +
gamma-ray multimessenger alerts, at 2020-07-04 at 15:48:46.812 UT, we
identified a low false alarm-rate (0.9764 per year) coincidence
between a single ANTARES neutrino and one Fermi LAT photon. An alert
was automatically generated and, after human review, distributed via
GCN. Alert details are as follows:

    Date:  2020-07-04
    Time:  15:53:48.812 UT
    R.A.:  17:01:41.93 (J2000)
    Dec.: -34:29:16.18 (J2000)
    r_90:  0.433 deg (90%-containment)
    FAR:   0.976 yr-1

ANTARES 200407 is a high-energy neutrino-induced muon event detected
by ANTARES (Ageron et al. 2011) with coordinates R.A. 16:59:20.4,
Dec. -34:30:57.6 (J2000) at 15:43:45 UT.

The minimum false alarm rate coincidence from our analysis associates
this neutrino with 1 Fermi LAT photon. The photon is detected at
15:53:48.624 UT with coordinates R.A. 17:01:52.08, Dec. -34:28:54.5
(J2000) and energy 8.49 GeV. The best-fit localization and uncertainty
for a point source yielding the ANTARES 200407 neutrino and this
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
1.02 years.

Details of the ANTARES + Fermi LAT coincidence search procedures are
provided in Ayala Solares et al. (AMON + ANTARES) 2019 (ApJ accepted,
ArXiv:1904.06420). 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).

The AMON alert for this coincidence is provided in GCN Alert format

NOTICE_DATE: Sat 04 July 2020  15:48:46.812 UT
NOTICE_TYPE: Fermi-LAT ANTARES coincidence
AMON_NUM: 1449036257
SRC_RA: 255.4246d {+17h 01m 41.9s} (J2000),
255.7550 {+17h 03m 01.2s} (current),
254.5994d {+16h 0258m 23.9s} (1950)
SRC_DEC: -34.4878d {-34d 29��� 16"} (J2000),
-34.5155d {-34d 30��� 56"} (current),
-34.4158d {-34d 24��� 57"} (1950)

SRC_ERROR90: 0.433 [deg, stat, 90% containment]
DISCOVERY_DATE: 19034 TJD;  186 DOY; 20/07/04 (yy/mm/dd)
DISCOVERY_TIME: 56926 SOD {15:48:46.812} UT
DELTA_T: 603.624 [sec]
SIGMA_T: 301.812 [sec]
FAR: 0.9764 [yr^-1]
SUN_POSTN: 104.3958d {+06h 57m 35s} 22.7739d {22d 46��� 26"}
SUN_DIST: 152.137 [deg] Sun_angle= 10.142 [hr] (West of Sun)
MOON_POSTN: 282.7167d {+18h 50m 52s} -24.9736d {-24d 58��� 25"}
MOON_DIST: 25.436 [deg]
GAL_COORDS: 350.1453, +04.5767 [deg] galactic lon,lat of the event

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