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GCN Circular 32683

GRB 221009A: Upper limits from HAWC 8 hours after trigger
2022-10-11T12:04:14Z (2 years ago)
Hugo Ayala at Pennsylvania State University <>
Hugo Ayala  (PSU) reports on behalf of the HAWC
collaboration (
reports observations of GRB 221009A which was detected by
Swift (Kennea et al. GCN #32635), Fermi-GBM (Veres et al. GCN #32636,
Lesage et al. GCN #32642), Fermi-LAT (Bissaldi et al. GCN #32637),
and the IPN (Svinkin et al. GCN #32641).

We use the position measured by Fermi LAT (GCN #32658), located at:
RA = 288.282, Dec = 19.495 (0.027 deg 90% containment radius)

This position started transiting over HAWC at 21:19:57 UTC on 2022/10/09
(~8 hours after the trigger time)  and ended at 03:42:07 UTC on 2022/10/10.

Assuming a power law spectra with index of -2.0 we found no significant
detection in the region. We proceeded to calculate the 95% upper limit on
the flux at 1 TeV: 4.16e-12 (TeV cm2 s)^-1

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 3.14 sr and
surveys <5/6 of the sky every day. It is sensitive to gamma rays from
300 GeV to 100 TeV.
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