Examining Two-Dimensional Luminosity-time Correlations for Gamma Ray Burst Radio Afterglows with VLA and ALMA

TL;DR

This study investigates radio afterglow light curves of gamma-ray bursts, revealing a correlation between luminosity and break time, and finds that radio break times are generally later than in X-ray and optical wavelengths, suggesting spectral evolution or long-lasting plateaus.

Contribution

First multi-wavelength analysis of the Dainotti correlation in radio GRB afterglows, demonstrating the existence of a similar luminosity-break time relation and comparing break times across wavelengths.

Findings

Radio GRB afterglows show a Dainotti-like correlation.

Radio break times are significantly later than in X-ray and optical.

No significant difference in burst duration distribution between broken and unbroken radio light curves.

Abstract

Gamma-ray burst (GRB) afterglow emission can be observed from sub-TeV to radio wavelengths, though only 6.6\% of observed GRBs present radio afterglows. We examine GRB radio light curves (LCs) to look for the presence of radio plateaus, resembling the plateaus observed in X-ray and optical. We analyze 404 GRBs from the literature with observed radio afterglow and fit 82 GRBs with at least 5 data points with a broken power law (BPL) model, requiring 4 parameters. From these, we find 18 GRBs that present a break feature resembling a plateau. We conduct the first multi-wavelength study of the Dainotti correlation between the luminosity $L_a$ and the rest-frame time of break $T_a^*$ for those 18 GRBs, concluding that the correlation exists and resembles the corresponding correlation in X-ray and optical wavelengths after correction for evolutionary effects. We compare the $T_a^*$ for the radio sample with $T_a^*$ values in X-ray and optical data (Dainotti et al. 2013, 2020b), finding significantly later break times in radio. We propose that this late break time and compatibility in slope suggests either a long-lasting plateau or the passage of a spectral break in the radio band. We also correct the distribution of the isotropic energy $E_{\rm iso}$ vs. the rest-frame burst duration $T^*_{90}$ for evolutionary effects and conclude that there is no significant difference between the $T^*_{90}$ distribution for the radio LCs with a break and those without.