An Observational Limit on the Earliest GRBs

Abstract

We predict the redshift of the first observable (i.e., in our past light cone) Gamma Ray Burst (GRB) and calculate the GRB-rate redshift distribution of the Population III stars at very early times (z=20-60). Using the last 2 years of data from Swift we place an upper limit on the efficiency (η_{GRB}) of GRB production per solar mass from the first generation of stars. We find that the first observable GRB is most likely to have formed at redshift 60. The observed rate of extremely high redshift GRBs (XRGs) is a subset of a group of 15 long GRBs per year, with no associated redshift and no optical afterglow counterparts, detected by Swift. Taking this maximal rate we get that η_{GRB}<1.1~10^{-4} GRBs per solar mass in stars. A more realistic evaluation, e.g., taking a subgroup of 5% of the total sample of Swift gives an upper limit of η_{GRB}<3.2~10^{-5} GRBs per solar mass.

6 Pages, 3 figures, submitted to MNRAS

References in corpus (6)

• The redshift distribution of SWIFT Gamma-Ray Bursts: evidence for evolution
• The first generation of stars in LCDM cosmology
• The Physics and Early History of the Intergalactic Medium
• Do long-duration GRBs follow star formation?
• The formation and gas content of high redshift galaxies and minihalos
• The First Stars in the Universe and Cosmic Reionization

Cited by in corpus (4)

• The Host Galaxies of Swift Dark Gamma-Ray Bursts: Observational Constraints on Highly Obscured and Very High-Redshift GRBs
• Observations of the Naked-Eye GRB 080319B: Implications of Nature's Brightest Explosion
• Star Formation History up to z = 7.4: Implications for Gamma-Ray Bursts and the Cosmic Metallicity Evolution
• Are There Any Redshift >8 Gamma-Ray Bursts in the BATSE Catalog?