GCN Circular 21683
Subject
LIGO/Virgo G298048: HAWC follow-up
Date
2017-08-24T19:35:19Z (7 years ago)
From
Israel Martinez-Castellanos at UMD/HAWC <imc@umd.edu>
I. Martinez-Castellanos (University of Maryland, College Park) and
A.J. Smith (University of Maryland, College Park) on behalf of the
HAWC Collaboration:
HAWC Collaboration performed a follow-up of LIGO trigger G298048. At the
time of the trigger no portion of the LV contour was visible to HAWC, so
no prompt follow-up was possible.
About 9hrs after the trigger the LV region transited through the HAWC FOV
(95% of the probability was covered), albeit with a large zenith angle,
which limits the sensitivity of our observations. 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
~2e-11 >1TeV cm^-2 s^-1 (~3 Crab units) at dec=-12 to about 6 times higher
at the edge of our FOV, dec=-25.
At the point of the optical counterpart candidate SSS17a/DLT17ck
(RA=13:09:48.09 DEC=-23:22:53.35) reported by Coulter et al. (LVC GCN
21529), Allam et al. (LVC GCN 21530), Yang et al. (LVC GCN 21531),
Melandri et al. (LVC GCN 21532), we obtain an 95% confidence level upper
limit for >1TeV assuming a -2.5 spectrum of 1.0e-10 cm^-2 s^-1. These
observations were made on 2017-08-17 between 19:57 UT and 23:25 UT with
culmination 9:00 hrs after the LV trigger.
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.