GRB 191016A: A Long Gamma-Ray Burst Detected by TESS

TL;DR

This paper reports the detection of the optical afterglow of GRB 191016A by TESS, providing insights into its properties, redshift, and the potential of TESS to observe similar GRB afterglows.

Contribution

First demonstration of TESS detecting a long GRB afterglow, with detailed analysis of its optical and high-energy properties, and estimation of TESS's GRB detection rate.

Findings

TESS detected the optical afterglow of GRB 191016A with a late peak at 2589.7 seconds.

Estimated redshift of the burst is approximately 3.29.

TESS is likely to detect about one GRB afterglow per year above its magnitude limit.

Abstract

The TESS exoplanet-hunting mission detected the rising and decaying optical afterglow of GRB 191016A, a long Gamma-Ray Burst (GRB) detected by Swift-BAT but without prompt XRT or UVOT follow-up due to proximity to the moon. The afterglow has a late peak at least 1000 seconds after the BAT trigger, with a brightest-detected TESS datapoint at 2589.7 s post-trigger. The burst was not detected by Fermi-LAT, but was detected by Fermi-GBM without triggering, possibly due to the gradual nature of rising light curve. Using ground-based photometry, we estimate a photometric redshift of $z_\mathrm{phot} = 3.29\pm{0.40}$. Combined with the high-energy emission and optical peak time derived from TESS, estimates of the bulk Lorentz factor $\Gamma_\mathrm{BL}$ range from $90-133$. The burst is relatively bright, with a peak optical magnitude in ground-based follow-up of $R=15.1$ mag. Using published distributions of GRB afterglows and considering the TESS sensitivity and sampling, we estimate that TESS is likely to detect $\sim1$ GRB afterglow per year above its magnitude limit.