HAWC-191019A

The HAWC Collaboration (http://www.hawc-observatory.org/collaboration/)
reports:

On October 19, 2019, at 20:11:06.18 UT, HAWC detected a burst signal
from its Burst Monitoring named HAWC-191019A.
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 0.2-second time window starting at
the reported trigger time.

The position of the alert is
RA (J200): 217.501deg
Dec (J2000): 25.81 deg
Location uncertainty (68% containment): 0.80 deg (statistical only).

The monitor system found that this alert has a false alarm rate
of 4.6e-3 alert(s) per year. We strongly encourage follow-up
observations of the HAWC alert region.

The initial automated alert is recorded in here:
https://gcn.gsfc.nasa.gov/notices_amon_hawc/8991_1097.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.

Alexis Coleiro (APC/Univ de Paris) and Damien Dornic (CPPM/CNRS) on behalf of the ANTARES Collaboration. <br>

Using data from the ANTARES detector, we have performed a follow-up analysis of the recently reported HAWC-191019A alert (GCN 26037
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 ). <br>

No up-going muon neutrino candidate events were detected within 3 degrees from the event coordinates over a time window of [T0-11min, T0+1h] where T0 is the time of the HAWC alert, and during which the potential source remained visible in the up-going field of view of ANTARES. A search over an extended time window of +1 day has also yielded no detection (35% visibility). <br>

This leads to a preliminary 90% confidence level upper limit on the muon-neutrino radiant fluence from a point source of about 90 GeV.cm^-2 over the energy range 6 TeV ��� 6 PeV (the range corresponding to 5-95% of the detectable flux) for an E^-2 power-law spectrum, and about 110 GeV.cm^-2 (1 TeV GeV - 550 TeV) for an E^-2.5 spectrum, computed for the time of the Swift Busrt Alert. <br>

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.

The HAWC Collaboration (http://www.hawc-observatory.org/collaboration/)
reports:

After human inspection, the trigger HAWC-191019A
is no longer considered to be of astrophysical
origin due to a data quality issue in the detector.