TITLE: GCN CIRCULAR NUMBER: 38551 SUBJECT: GRB241212A: OHP/T193 optical observations DATE: 24/12/13 10:32:53 GMT FROM: Christophe Adami at LAM christophe.adami@lam.fr

C. Adami (LAM/Pytheas/AMU), J. Schmitt (OHP/Pytheas/AMU), S. Basa (LAM/OHP/Pytheas/AMU) report on behalf of a larger collaboration:

We observed the field of GRB241212A (Fermi GBM team, GCN 38540; Zhang Li et al., GCN 38541; Joshi et al., GCN 38544; Qiu et al., GCN 38545; Zhe Kang et al., GCN 38546) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. Six exposures were obtained in the Y-band (6x300s) with the MISTRAL red mode during technical time from 2024 12 December 18:43 UT to 2024 12 December 19:15 UT (~+9.5h after detection). The moon was at an illumination of ~92% and at a distance of 13deg from target.

We do not detect the SVOM VT GRB counterpart provided by Qiu et al. (GCN 38545). The combined frame has a detection upper limit of Y~19.25+/-0.6 (5sigma limit). The photometric calibration was performed using objects from the PanSTARRS catalog. The magnitude is not corrected for Galactic extinction.

We acknowledge the excellent support from Observatoire de Haute-Provence, in particular Jean Pierre Troncin and the SOPHIE observers Guillaume Hebrard and Florian Destriez.

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