TITLE: GCN CIRCULAR NUMBER: 21759 SUBJECT: LIGO/Virgo G299232: HAWC follow-up DATE: 17/08/30 02:03:26 GMT FROM: Israel Martinez-Castellanos at UMD/HAWC I. Martinez-Castellanos (University of Maryland, College Park) and A.J. Smith (University of Maryland, College Park) on behalf of the HAWC Collaboration: The HAWC Collaboration performed a follow-up of LIGO trigger G299232. At the time of the trigger the HAWC local zenith was oriented toward (α, δ) = (75.0°, 19.0°), so the LV contour had just set in our field of view and no prompt follow-up was possible. We searched for long time scale emission during the following transit. The observations ranged from T0+28ks to T0+87ks. In total 70% of the probability space was covered. There were no >5 sigma points observed. For a single transit, the 5 sigma sensitivity to a power law spectrum with a -2.5 index ranges from ~1.9e-11 >1TeV cm^-2 s^-1 (~1 Crab unit) at dec=-19 to about 10 times higher at the edge of our FOV (45˚ from zenith). At the point of the source reported by Swift/UVOT (RA=01h40m08.55s DEC=+34d34'03.6", LVC GCN 21733) we obtain an 95% confidence level upper limit for >1TeV assuming a -2.5 spectrum of 4.3e-12 cm^-2 s^-1. These observations were made from T0+62ks to T0+85ks. We found no significant excess on the error radius corresponding to the neutrino reported by IceCube (RA=28.2˚ DEC= 44.8˚, LVC GCN 21698). For the location of maximum excess in the error radius we obtain an 95% confidence level upper limit for >1TeV assuming a -2.5 spectrum of 2.8e-11 cm^-2 s^-1. These observations were made from T0+64ks to T0+86ks. 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.