Properties of Low Luminosity Afterglow Gamma-ray Bursts

TL;DR

This study characterizes a subset of gamma-ray bursts with low luminosity X-ray afterglows, revealing they are a nearby, distinct population with unique properties, including faint prompt emissions and some outliers of the Amati relation.

Contribution

The paper identifies and analyzes a distinct population of low luminosity afterglow GRBs, highlighting their unique properties and potential implications for GRB models.

Findings

LLA GRBs are a nearby, distinct population.

They are faint during their prompt phase.

Many are associated with supernovae, affecting modeling.

Abstract

Aims: We characterize a sample of Gamma-Ray Bursts with low luminosity X-ray afterglows (LLA GRBs), and study their properties. Method: We select a sample consisting of the 12\% faintest X-ray afterglows from the total population of long GRBs (lGRBs) with known redshift. We study their intrinsic properties (spectral index, decay index, distance, luminosity, isotropic radiated energy and peak energy) to assess whether they belong to the same population than the brighter afterglow events. Results: We present strong evidences that these events belong to a population of nearby events, different from that of the general population of lGRBs. These events are faint during their prompt phase, and include the few possible outliers of the Amati relation. Out of 14 GRB-SN associations, 9 are in LLA GRB sample, prompting for caution when using SN templates in observational and theoretical models for the general lGRBs population.