Accessing the population of high-redshift Gamma Ray Bursts

Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Date Issued
2015
Author(s)
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Osborne, J. P.
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O'Brien, P.
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Tanvir, N.
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Willingale, D.
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Basa, S.
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Burlon, D.
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Frontera, F.
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Götz, D.
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Vergani, S. D.
DOI
10.1093/mnras/stv183
Description
We acknowledge a Prin–INAF 2011 grant (1.05.01.09.15) and ASI–INAF contract (I/004/11/1). We thank the anonymous referee for his/her valuable comments that improved the manuscript. Specific simulations for energy ranges not considered in this paper can be provided on request. JPO acknowledges partial support from the UK Space Agency. DB is funded through ARC grant DP110102034. DG acknowledges the financial support of the UnivEarthS Labex program at Sorbonne Paris Cité (ANR-10-LABX-0023 and ANR-11-IDEX-0005-02).
Abstract
Gamma Ray Bursts (GRBs) are a powerful probe of the high-redshift Universe. We present a tool to estimate the detection rate of high-z GRBs by a generic detector with defined energy band and sensitivity. We base this on a population model that reproduces the observed properties of GRBs detected by Swift, Fermi and CGRO in the hard X-ray and γ-ray bands. We provide the expected cumulative distributions of the flux and fluence of simulated GRBs in different energy bands. We show that scintillator detectors, operating at relatively high energies (e.g. tens of keV to the MeV), can detect only the most luminous GRBs at high redshifts due to the link between the peak spectral energy and the luminosity (Epeak-Liso) of GRBs. We show that the best strategy for catching the largest number of high-z bursts is to go softer (e.g. in the soft X-ray band) but with a very high sensitivity. For instance, an imaging soft X-ray detector operating in the 0.2-5 keV energy band reaching a sensitivity, corresponding to a fluence, of ̃10-8 erg cm-2 is expected to detect ≈40 GRBs yr-1 sr-1 at z ≥ 5 (≈3 GRBs yr-1 sr-1 at z ≥ 10). Once high-z GRBs are detected the principal issue is to secure their redshift. To this aim we estimate their NIR afterglow flux at relatively early times and evaluate the effectiveness of following them up and construct usable samples of events with any forthcoming GRB mission dedicated to explore the high-z Universe.
Volume
448
Issue
3
Start page
2514
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