TITLE:   GCN CIRCULAR
NUMBER:  42575
SUBJECT: EP251102a: OHP/T193 optical observations
DATE:    25/11/04 11:32:43 GMT
FROM:    Christophe Adami at LAM <christophe.adami@lam.fr>

C. Adami (LAM/Pytheas/AMU), N.A. Rakotondrainibe  (LAM), B. Schneider (LAM), S. Basa (UAR Pytheas), E. Le Floc'h (CEA/Irfu) report on behalf of the MISTRAL GRB collaboration:

We carried out observations of the EP251102a (Schneider et al., GCN 42544; Eyles-Ferris et al., GCN 42546; Liang et al., GCN 42548; Mo et al., GCN 42563) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained 75 min (15 exposures of 5 min) in the r-band at a midtime of 2025-11-04 03:34:45 UT corresponding to T-T0 = 30.2064 hours.

The afterglow is detected in r’ after image subtraction performed relative to r-band images from  PanSTARRS. We measured the following preliminary magnitude:

r’ = 20.94 +/- 0.07

The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the STDWeb/STDPipe tools (Karpov 2025), is in the AB system, and is not corrected for Galactic extinction.

We acknowledge the excellent support from the Observatoire de Haute-Provence and in particular Yoann Degot-Longhi.