Luminosity function and jet structure of Gamma Ray Bursts

Abstract

The structure of Gamma Ray Burst (GRB) jets impacts on their prompt and afterglow emission properties. The jet of GRBs could be uniform, with constant energy per unit solid angle within the jet aperture, or it could instead be structured, namely with energy and velocity that depend on the angular distance from the axis of the jet. We try to get some insight about the still unknown structure of GRBs by studying their luminosity function. We show that low (1e46-1e48 erg/s) and high (i.e. with L > 1e50 erg/s) luminosity GRBs can be described by a unique luminosity function, which is also consistent with current lower limits in the intermediate luminosity range (1e48-1e50} erg/s). We derive analytical expressions for the luminosity function of GRBs in uniform and structured jet models and compare them with the data. Uniform jets can reproduce the entire luminosity function with reasonable values of the free parameters. A structured jet can also fit adequately the current data, provided that the energy within the jet is relatively strongly structured, i.e. E propto theta^{-k} with k > 4. The classical E propto theta^{-2} structured jet model is excluded by the current data.

11 pages, 2 tables, 7 figures, submitted to MNRAS

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Cited by in corpus (13)

• Gravitational Waves and Gamma-rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A
• Electromagnetic Counterparts to Structured Jets from Gravitational Wave Detected Mergers
• Off-axis short GRBs from structured jets as counterparts to GW events
• Structure of Gamma-Ray Burst jets: intrinsic versus apparent properties
• The Needle in the 100 deg2 Haystack: Uncovering Afterglows of Fermi GRBs with the Palomar Transient Factory
• Unveiling the population of orphan Gamma Ray Bursts
• Accessing the population of high redshift Gamma Ray Bursts
• Revisiting the luminosity and redshift distributions of long gamma-ray bursts
• Precessing magnetars as central engines in short gamma-ray bursts
• Jet-driven and jet-less fireballs from compact binary mergers
• Modelling the luminosity function of long Gamma Ray Bursts using SWIFT and FERMI
• The pulse luminosity function of Swift gamma-ray bursts
• Gamma-ray burst jets: uniform or structured?