Luminosity Selection for Gamma Ray Burst

TL;DR

This paper investigates how relativistic beaming and viewing angle variations affect the intrinsic luminosity function of Gamma Ray Bursts, using median luminosity as a robust diagnostic to compare models with observational data.

Contribution

It introduces a statistical median luminosity test to analyze GRB luminosity models considering jet orientation and detection biases.

Findings

Median luminosity is insensitive to the jet's maximum on-axis luminosity.

The method accounts for undetected GRBs at various redshifts.

Simulation results align with Swift observational data.

Abstract

There exists an inevitable scatter in intrinsic luminosity of Gamma Ray Bursts(GRBs). If there is relativistic beaming in the source, viewing angle variation necessarily introduces variation in the intrinsic luminosity function (ILF). Scatter in the ILF can cause a selection bias where distant sources that are detected have a larger median luminosity than those detected close by. Median luminosity divides any given population into equal halves. When the functional form of a distribution is unknown, it can be a more robust diagnostic than any that use trial functional forms. In this work we employ a statistical test based on median luminosity and apply it to test a class of models for GRBs. We assume that the GRB jet has a finite opening angle and that the orientation of the GRB jet is random relative to the observer.We calculate $L_{median}$ as a function of redshift by simulating GRBs empirically, theoretically and use the luminosity vs redshift {\it Swift} data in order to compare the theoretical results with the observed ones. The method accounts for the fact that at some redshifts there may be some GRBs that go undetected. We find that $L_{median}$ is extremely insensitive to the on-axis (i.e. maximal) luminosity of the jet.