Search for Gamma Ray Bursts at Chacaltaya

TL;DR

This study used the INCA air shower array at high altitude to search for gamma ray bursts in the GeV-TeV range, setting the lowest upper limits in the sub-TeV region to date.

Contribution

First ground-based search for GRBs at high altitude using the single particle technique, establishing new low upper limits in the GeV-TeV energy range.

Findings

No significant gamma ray burst signals detected.

Upper limits on energy fluence are the lowest ever in the sub-TeV range.

Results constrain models of high-energy emission from GRBs.

Abstract

A search for Gamma Ray Bursts in the GeV-TeV energy range has been performed by INCA, an air shower array working at 5200 m of altitude at the Chacaltaya Laboratory (Bolivia). The altitude of the detector and the use of the "single particle technique" allows to lower the energy threshold up to few GeVs. No significant signals are observed during the occurrence of 125 GRBs detected by BATSE, and the obtained upper limits on the energy fluence in the interval 1-1000(100) GeV range from 3.2(8.6) 10^-5 to 2.6(7.0) 10^-2 erg/cm^2 depending on the zenith angle of the events. These limits, thanks to the extreme altitude of INCA, are the lowest ever obtained in the sub-TeV energy region by a ground based esperiment.