Jun Kakuwa, Kohta Murase, Kenji Toma, Susumu Inoue, Ryo Yamazaki, Kunihito Ioka
We discuss the prospects for the detection of gamma-ray bursts (GRBs) by the
Cherenkov Telescope Array (CTA), the next generation, ground-based facility of
Imaging Atmospheric Cherenkov Telescopes (IACTs) operating above a few tens of
GeV. By virtue of its fast slewing capabilities, the lower energy threshold
compared to current IACTs, and the much larger effective area compared to
satellite instruments, CTA can measure the spectra and variability of GRBs with
excellent photon statistics at multi-GeV energies, which would revolutionize
our understanding of the physics of GRBs, test their validity as the origin of
ultra-high-energy cosmic rays, and provide powerful probes of the extragalactic
background light as well as Lorentz-invariance violation. Employing a model of
the GRB population whose properties are broadly consistent with observations by
Swift as well as the Gamma-ray Burst Monitor (GBM) and Large Area Telescope
(LAT) onboard Fermi, we simulate follow-up observations of GRBs with the Large
Size Telescopes (LSTs), the component of CTA with the fastest slew speed and
the best sensitivity at energies below a few hundred GeV. For our fiducial
assumptions, we foresee that the LSTs can detect ~0.1--0.2 GRBs per year during
the prompt phase and ~1 per year in the afterglow phase, considering only one
array site and both GBM and the Space-based multi-band astronomical Variable
Object Monitor (SVOM) as the alert instruments. The expected distribution of
redshift and photon counts are presented, showing that despite the modest event
rate, hundreds or more multi-GeV photons can be anticipated from a single burst
once they are detected. We also study how the detection rate depends on the
intrinsic GRB properties and the delay time between the burst trigger and the
follow-up observation.
View original:
http://arxiv.org/abs/1112.5940
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