A Radio-Selected Sample of Gamma Ray Burst Afterglows

TL;DR

This paper compiles and analyzes 14 years of radio afterglow data from 304 gamma-ray bursts, revealing consistent detection rates, typical light curve features, and relationships with GRB properties, while also predicting future observations with advanced telescopes.

Contribution

It provides the largest radio afterglow catalog to date, offering statistical insights and predictive models for GRB radio emissions based on multiwavelength data.

Findings

Radio afterglow detection rate remains at 31% before and after Swift launch.

Canonical radio light curve peaks at 3-6 days with median luminosity of 10^31 erg s^-1 Hz^-1.

Short-hard bursts and other classes are significantly fainter in radio than long-duration GRBs.

Abstract

We present a catalog of radio afterglow observations of gamma-ray bursts (GRBs) over a 14 year period from 1997 to 2011. Our sample of 304 afterglows consists of 2995 flux density measurements (including upper limits) at frequencies between 0.6 GHz and 660 GHz, with the majority of data taken at 8.5 GHz frequency band (1539 measurements). We use this dataset to carry out a statistical analysis of the radio-selected sample. The detection rate of radio afterglows has stayed unchanged almost at 31% before and after the launch of the {\em Swift} satellite. The canonical long-duration GRB radio light curve at 8.5 GHz peaks at 3-6 days in the source rest frame, with a median peak luminosity of $10^{31}$ erg s$^{-1}$ Hz$^{-1}$. The peak radio luminosities for short-hard bursts, X-ray flashes and the supernova-GRB classes are an order of magnitude or more fainter than this value. There are clear relationships between the detectability of a radio afterglow and the fluence or energy of a GRB, and the X-ray or optical brightness of the afterglow. However, we find few significant correlations between these same GRB and afterglow properties and the peak radio flux density. We also produce synthetic light curves at centimeter (cm) and millimeter (mm) bands using a range of blastwave and microphysics parameters derived from multiwavelength afterglow modeling, and we use them to compare to the radio sample. Finding agreement, we extrapolate this behavior to predict the cm and mm behavior of GRBs observed by the Expanded Very Large Array and the Atacama Large Millimeter Array.