Search of extended or delayed TeV emission from GRBs with HAWC

TL;DR

This paper reports on a search for delayed or extended TeV gamma-ray emission from gamma-ray bursts using the HAWC observatory, providing upper limits and discussing implications for high-energy emission models.

Contribution

First search for delayed or extended TeV emission from GRBs with HAWC, setting upper limits and exploring theoretical implications.

Findings

No significant TeV emission detected from the GRBs studied.

Established upper limits on TeV emission from GRBs.

Discussed implications for models of high-energy GRB emission.

Abstract

Gamma-ray bursts (GRBs) are among the most luminous sources in the universe and the nature of their emission up to very high energy is one of the most important open issue connected with the study of these peculiar events. The High Altitude Water Cherenkov (HAWC) gamma-ray observatory, installed at an altitude of 4100 m a. s. l. in the state of Puebla (Mexico), has completed its second year of full operations. Thanks to its instantaneous field of view of ~2 sr and its high duty cycle ($\ge$ 95%), HAWC is an ideal instrument for the study of transient phenomena such as GRBs. We performed a search for TeV emission delayed with respect to, and of longer duration than the prompt emission observed by satellites. We present here the results obtained by observing at the position of a sample of GRBs detected by the Fermi and Swift satellites from December 2014 to February 2017. The upper limits resulting from this analysis are presented and theoretical implications are discussed.