TITLE: GCN CIRCULAR NUMBER: 36286 SUBJECT: LIGO/Virgo/KAGRA S240422ed: No significant counterpart candidates in HAWC observations DATE: 24/04/24 16:02:42 GMT FROM: Hugo Ayala at Pennsylvania State University hgayala@psu.edu
The HAWC Collaboration (https://www.hawc-observatory.org) reports:
The HAWC Collaboration performed a follow-up of the gravitational wave trigger S240422ed (GCN 36236). At the time of the trigger the HAWC local zenith was oriented towards (RA, Dec) = (77.6 deg, 19.0 deg). 36% 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 49.8deg to 60deg for the area searched in this analysis. The 5sigma detection sensitivity to a 1s (100s) burst in the 80-800GeV energy range goes from 9.9e-5 erg/cm^2 to 4.4e-4 erg/cm^2 (5.6e-4 erg/cm^2 to 2.5e-03 erg/cm^2), depending on the zenith angle.
A list of some of the hotspots found in the search is shown below. We found that one of the galaxies that are mentioned in GCN 36235 is close to one of the observed hotspots. No hotspot was close to the updated list in GCN 36243. We mark with a “>” the hotspots that still show up in the updated localization of the GW (GCN 36240).
Timescale 3 seconds RA Dec Unc. TS Galaxy 126.21 -8.61 0.83 10.97
126.91 -16.10 0.85 11.47
Timescale 10 seconds RA Dec Unc. TS Galaxy 124.80 -9.97 0.49 12.31
126.65 -16.49 0.71 9.27
Timescale 30 seconds RA Dec Unc. TS Galaxy 124.80 -9.97 0.49 9.01
127.53 -15.71 0.64 9.15
Timescale 100 seconds RA Dec Unc. TS Galaxy 110.65 -27.95 0.50 9.23 113.99 -20.42 0.37 10.23 114.08 -19.87 0.50 9.29 114.26 -21.94 0.52 11.29 120.94 -13.32 0.59 13.33 WISEA J080028.14-134847.4 (0.95deg) 128.23 -10.20 0.39 12.79
129.46 -16.49 0.55 12.06
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.
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