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

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Krista Lynne Smith, Ryan Ridden-Harper, Michael Fausnaugh et al.,GRB 191016A: A Long Gamma-Ray Burst Detected by TESS,


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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 zphot=3.29±0.40. Combined with the high-energy emission and optical peak time derived from TESS, estimates of the bulk Lorentz factor ΓBL 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 ∼1 GRB afterglow per year above its magnitude limit.