TITLE:   GCN CIRCULAR
NUMBER:  34762
SUBJECT: GRB 230812B: r'-band observations from MISTRAL at Observatoire de Haute-Provence
DATE:    23/09/24 19:28:39 GMT
FROM:    Christophe Adami at LAM <christophe.adami@lam.fr>

P. Amram, C. Adami, S. Basa (LAM/Pythéas), T. Adami (ENS Paris-Saclay), B. 
Schneider (MIT), A. Saccardi, S. D. Vergani, (GEPI, Obs. de Paris), S. 
Antier, A. de Ugarte Postigo (OCA), E. Le Floc'h, D. Götz, F. Schüssler, 
D. Turpin (CEA-Saclay), report, on behalf of a larger collaboration:

We observed the field of GRB 230812B (Fermi GBM Team GCN, 34386 and all 
subsequent GCNs) using the MISTRAL spectro-imager of Observatoire de Haute 
Provence (OHP) in imaging mode. We obtained during the 2023 09 22 night 12x600s 
exposure in the r'-band with a mid-epoch of 20:30 UT.

We derive the following photometry, calibrated against the Pan-STARRS catalog, 
not corrected for the underlying galaxy, and not corrected for Galactic dust reddening:

2023 09 22 20:30 UT r' = 22.37 +/- 0.14

We acknowledge the excellent support from Yoann Degot-Longhi (Observatoire de Haute 
Provence) and we thank Isabelle Boisse.