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GCN Circular 35047

GRB 231106A: TESS identification of candidate optical counterpart
2023-11-15T22:20:46Z (4 months ago)
Rahul Jayaraman at MIT <>
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R. Jayaraman (MIT/MKI), R. Vanderspek (MIT/MKI), M.M. Fausnaugh (TTU), G. Mo (MIT/LIGO), and G.R. Ricker (MIT/MKI) report:

The Transiting Exoplanet Survey Satellite (TESS; Ricker et al. JATIS 1 2015) was observing 91% of the Fermi-GBM localization region for the gamma-ray burst GRB 231106A (GCN 34956). TESS observed this region at a 200 second cadence continuously from 1.5 days before the trigger to 6.4 days after the trigger. The GRB occurred during TESS observational Sector 71, and most of the GBM localization fell within Camera 4, CCD 1.

We inspected the full-frame image (FFI) from the publicly available TICA data archived at MAST ( at the time of the Fermi trigger and identified a bright point source not present in previous TESS images. This point source is located at RA = 113.4482, Dec = 29.2245 (uncertainty 1-2"), which is 3.6° from the center of the Fermi-GBM error region, and is located within the 39.7% credible region of the Fermi sky map. We extracted a light curve for this source from the calibrated TESS FFIs produced by TICA (Fausnaugh et al. RNAAS 2020) using difference imaging and forced photometry. Our analysis procedure is described in Fausnaugh et al. 2023 (ApJ 956(2):108).

TESS observations show that this optical transient rises rapidly (in less than 200 seconds), peaks at a magnitude of 13.8 in the TESS band (600 nm–1000 nm), and then decays to the detection limit within 2000 seconds, with a power-law index of -0.95 ± 0.28. The 3-sigma detection limit around the time of the trigger was 17.5.

This circular includes data collected with the TESS mission, obtained from the MAST data archive at the Space Telescope Science Institute (STScI). Funding for the TESS mission is provided by the NASA Explorer Program. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5–26555.
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