[vsnet-grb-info 23508] LIGO/Virgo S190901ap: No counterpart candidates in HAWC observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25607
SUBJECT: LIGO/Virgo S190901ap: No counterpart candidates in HAWC observations
DATE:    19/09/02 02:11:08 GMT
FROM:    Israel Martinez-Castellanos at UMD/HAWC  <imc at umd.edu>

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

The HAWC Collaboration performed a follow-up of the gravitational wave
trigger S190901ap (GCN #25606). At the time of the trigger the HAWC
local zenith was oriented towards (RA, Dec) = (236.1 deg, 19.1 deg).
31% 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 0 deg to 45 deg for the area searched in this
analysis. The 5sigma detection sensitivity to a 1s (100s) burst in the
80-800GeV energy range goes from 1.2e-6 erg/cm^2 to 1.1e-4 erg/cm^2
(6.4e-6 erg/cm^2 to 5.0e-4 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.