TITLE: GCN CIRCULAR NUMBER: 41324 SUBJECT: GRB 250812A: TRT likely optical counterpart detection DATE: 25/08/12 09:35:34 GMT FROM: J. An jiean0813@foxmail.com

L.B. He (NAOC), K. Noysena, K. Chanchaiworawit, S. Tinyanont (NARIT), S.Y. Fu (HUST), J. An, X. Liu, Z.P. Zhu, S.Q. Jiang, D. Xu (NAOC) report on behalf of a large collaboration:

We observed the field of GRB 250812A (Xin et al., GCN 41322), using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Cerro Tololo Inter-American Observatory, Chile. Observations started at 04:32:00 UTC on 2025-08-12, i.e., ~1.8 hr after the SVOM/ECLAIRs trigger and a series of frames in the r band were obtained.

In our stacked image, we detect an uncatalogued source within the SVOM/ECLAIRs error circle at coordinates:

R.A.(J2000) = 02:11:13.72 = 32.80715 Dec.(J2000) = -43:09:49.21 = -43.16367

with an uncertainty of ~0.5 arcsec. We measure a preliminary magnitude of r ~ 18.8, calibrated with Legacy catalog and not corrected for Galactic extinction.

We suggest this is likely the optical counterpart of GRB 250812A.

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