GCN Circular 24102

I. Martinez-Castellanos (University of Maryland) reports on behalf of the
HAWC Collaboration:

The HAWC Collaboration performed a follow-up of the gravitational wave
triggerS190412m (GCN #24098). At the time of the trigger the HAWC local
zenith was oriented towards (RA, Dec) = (185.3deg, 19.1deg). 99% of the GW
candidate sky location probability fell within our observable field of view
(0-45 deg zenith angle).

We performed a search for a short timescale emission using 6 sliding time
windows (dt = 0.3s, 1s, 3s, 10s, 30s and  100s), shifted forward in time by
20% of their width. We searched the 95% probability containment area in a
timescale-dependent time period, from t0-5dt to t0+10dt, where t0 is the
time of the GW trigger. No significant gamma-ray detection above the
background was observed.

The sensitivity of this analysis is greatly dependent on zenith angle,
ranging from 4.5deg to 43.6deg for the area searched in this analysis. The
5sigma detection sensitivity to a 1s (100s) burst in the 80-800GeV energy
ranges from 1.2e-06 erg/cm^2 to 7.8e-05 erg/cm^2  (6.7e-06 erg/cm^2
to 3.5e-04 erg/cm^2), depending on the zenith angle.

HAWC is a TeV gamma ray water Cherenkov array located in the state of
Puebla, Mexico. It is sensitive to the energy range ~0.1-100TeV, and
monitors 2/3 of the sky every day with an instantaneous field-of-view of ~2
sr.