TITLE:   GCN CIRCULAR
NUMBER:  40744
SUBJECT: sb25061207/SVOM: T120 OHP optical upper limit
DATE:    25/06/16 10:28:28 GMT
FROM:    Christophe Adami at LAM <christophe.adami@lam.fr>

C. Adami (LAM/Pytheas/AMU), B. Schneider (LAM), Y. Degot-Longui (Pytheas/OHP), S. Basa (LAM/OHP/Pytheas/AMU), E. Le Floc'h (CEA/Irfu), report on behalf of a larger collaboration:

We observed the field of the SVOM sb25061207 X-ray transient (Zhang et al., GCN 40697; Li et al., GCN 40707; Evans et al.,GCN 40711; Li et al., GCN 40707; Zhang et al., GCN 40697) using the T120cm telescope at Observatoire de Haute-Provence (France). We obtained 54.5 minutes in the r-band, from 2025-06-12T20:32:03.91 to 2025-06-12T21:44:45.14 (from 9.9 to 11.3 hr after the trigger).

In the stacked image, we do not detect the VT optical counterpart (Li et al., GCN 40707) down to the following 3-sigma limit (AB) measured with STDWeb/STDPipe tools (Karpov 2025):

r > 22.1

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

We acknowledge the excellent support from Observatoire de Haute-Provence and in particular the students and professors from the summer camp OHP 2025 (Institut Origines).