GCN Circular 21709

I. Martinez-Castellanos (University of Maryland, College Park),
C. M. Hui (NASA/MSFC) and A.J. Smith (University of Maryland, College Park)
on behalf of the HAWC Collaboration:

HAWC Collaboration performed a follow-up of LIGO trigger G298389. At the
time
of the trigger no portion of the LV contour was visible to HAWC, so no
prompt
follow-up was possible.

The GW probability region transited through the HAWC FOV shortly after
trigger
time, with the maximum probability point (RA=158.0deg,Dec=1.6deg) entering
our FOV at T0 + 2 ks and leaving the FOV at T0 + 22 ks. We integrated this
period
and searched for highly significant events (94% of the probability was
covered).
There were no >5 sigma points observed during this transit. For a single
transit,
the 5 sigma sensitivity to a power law spectrum with a -2.5 index ranges
from
~1.7e-11 >1TeV cm^-2 s^-1 (~1 Crab units) at dec=15 to about 10 times
higher at
the edge of our FOV, dec=-25.

HAWC is a TeV gamma ray water Cherenkov array located in the state of
Puebla,
Mexico. It is sensitive to the energy range ~0.5-100TeV, and monitors 2/3
of the
sky every day with an instantaneous field-of-view of ~2 sr.