The Optical Luminosity-Time Correlation for More Than 100 Gamma-Ray Burst Afterglows

TL;DR

This study analyzes over 100 gamma-ray burst afterglows, revealing an optical luminosity-time correlation similar to X-ray plateaus, confirming achromaticity and providing the largest optical plateau dataset to date.

Contribution

It is the first comprehensive analysis demonstrating a robust optical luminosity-time correlation in GRB afterglows with the largest sample of optical plateaus.

Findings

Optical plateaus are achromatic with X-ray plateaus.

The optical luminosity-time correlation is confirmed with minimal scatter.

Largest compilation of optical plateau data to date.

Abstract

Gamma-Ray Bursts (GRBs) are fascinating events due to their panchromatic nature. Their afterglow emission is observed from sub-TeV energies to radio wavelengths. We investigate GRBs that present an optical plateau, leveraging on the resemblance with the X-ray plateau shown in many GRB light curves (LCs). We comprehensively analyze all published GRBs with known redshifts and optical plateau observed mostly by the Neil Gehrels Swift Observatory (Swift). We fit 267 optical LCs and show the existence of the plateau in 102 cases, which is the largest compilation so far of optical plateaus. For 56 Swift GRBs with optical and X-ray plateaus, we compare the rest-frame end time at both wavelengths (T*_opt , T*_X), and conclude that the plateau is achromatic between T*_opt and T*_X. We also confirm the existence of the two-dimensional relations between T*_opt and the optical luminosity at the end of the plateau emission, which resembles the same luminosity-time correlation in X-rays (Dainotti et al. 2013). The existence of this optical correlation has been demonstrated for the largest sample of optical plateaus in the literature to date. The squared scatter in this optical correlation is smallest for the subset of the Gold GRBs with a decrease in the scatter equivalent to 52.4% when compared to the scatter of the entire GRB sample.