Broad-band Spectral Modeling of Prompt Emission from Gamma-Ray Bursts Observed by the Transiting Exoplanet Survey Satellite

TL;DR

This study analyzes prompt optical and gamma-ray emissions from 24 GRBs observed by TESS, fitting spectral models to understand their physical processes and identify cases of optical excess or extinction effects.

Contribution

It provides the first comprehensive spectral modeling of GRB prompt emissions across optical to gamma-ray wavelengths using TESS data.

Findings

In 4 cases, optical flux matches high-energy extrapolation within 1-sigma.

One case shows significant optical excess over the extrapolation.

Most cases (17) overpredict optical flux, likely due to dust extinction.

Abstract

Optical observations of gamma-ray bursts (GRBs) contemporaneous with their prompt high-energy emission are rare, but they can provide insights into the physical processes underlying these explosive events. The Transiting Exoplanet Survey Satellite's (TESS) large field of view and continuous observation capabilities make it uniquely positioned to detect and characterize prompt optical flashes from GRBs. In this work, we fit phenomenological models to the gamma-ray through optical spectral energy distributions (SEDs) of 24 bursts with arcsecond-level localizations that fell within the TESS field of view between 2018 July and 2024 December. In four cases, the extrapolation of the high-energy SED agrees with the observed optical flux to within 1-$\sigma$. In one case, there is a significant excess of optical flux relative to the extrapolation. In two cases, upper limits from TESS did not constrain the optical portion of the SED. In the remaining 17 cases, the optical flux is overpredicted by the extrapolation from high energies. This discrepancy could be explained by dust extinction in the host galaxy.