A Comprehensive Investigation of Gamma-Ray Burst Afterglows Detected by TESS

TL;DR

This study leverages TESS's continuous sky monitoring to detect and analyze optical afterglows of gamma-ray bursts, identifying new candidates and demonstrating TESS's potential in GRB localization and afterglow observation.

Contribution

First extensive search for GRB afterglows in TESS archival data, discovering new high-likelihood candidates and modeling their light curves to estimate burst parameters.

Findings

Detected 11 candidate afterglows coincident with reported GRBs

Identified 3 high-likelihood new afterglow detections by TESS

Estimated an average delay of 740 seconds between burst and afterglow onset

Abstract

Gamma-ray bursts produce afterglows that can be observed across the electromagnetic spectrum and can provide insight into the nature of their progenitors. While most telescopes that observe afterglows are designed to rapidly react to trigger information, the Transiting Exoplanet Survey Satellite (TESS) continuously monitors sections of the sky at cadences between 30 minutes and 200 seconds. This provides TESS with the capability of serendipitously observing the optical afterglow of GRBs. We conduct the first extensive search for afterglows of known GRBs in archival TESS data reduced with the TESSreduce package, and detect 11 candidate signals that are temporally coincident with reported burst times. We classify 3 of these as high-likelihood GRB afterglows previously unknown to have been detected by TESS, one of which has no other afterglow detection reported on the Gamma-ray Coordinates Network. We classify 5 candidates as tentative and the remainder as unlikely. Using the afterglowpy package, we model each of the candidate light curves with a Gaussian and a top hat model to estimate burst parameters; we find that a mean time delay of $740\pm690\,$s between the explosion and afterglow onset is required to perform these fits. The high cadence and large field of view make TESS a powerful instrument for localising GRBs, with the potential to observe afterglows in cases when no other backup photometry is possible, and at timescales previously unreachable by optical telescopes.