TITLE: GCN CIRCULAR NUMBER: 39157 SUBJECT: GRB 250205A: OHP/T193 optical counterpart candidate DATE: 25/02/05 23:18:19 GMT FROM: Benjamin Schneider at MIT bschn@mit.edu

B. Schneider (LAM) and C. Adami (LAM/Pytheas/AMU)

We observed the field of the GRB 250205A (Saccardi et al., GCN 39154) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained three exposures (300 s + 2x500 s) in the r-band starting at 22:06:27UT on 2025-02-05 (42 min after the trigger). In the stacked image, we clearly detected a new source not visible in the Legacy Survey and consistent with the MXT error at:

RA(J200) = 7:34:02.62 DEC(J200) = +32:22:18.98 with an uncertainty of 0.5 arcsec.

The preliminary magnitude derived for that source is

r = 21.01 +/- 0.07 mag (AB)

The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the magnitude is not corrected for Galactic extinction.

This source is consistent with the one reported by Gompertz et al. GCN 39156.

Further observations are ongoing.

We acknowledge the excellent support from Observatoire de Haute-Provence and in particular Jean-Pierre Troncin for the MISTRAL observations.

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