GCN Circular 42421
Subject
GRB 251023B: OHP/T193 optical observations
Event
Date
2025-10-24T13:26:31Z (4 days ago)
From
Ny Avo Rakotondrainibe at LAM <nyavo.rakotobe@gmail.com>
Via
Web form
C. Adami (LAM/Pytheas/AMU), N.A. Rakotondrainibe (LAM), E. Le Floc'h (CEA/Irfu), report on behalf of the MISTRAL GRB collaboration:
We carried out observations of GRB 251023B (Cheung et al., GCN 42407; Mandarakas et al., GCN 42404; Nakahira et al., GCN 42402; Evans et al., GCN 42401; Kang et al., GCN 42392) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained 6 exposures of 15 min in the r-band at a midtime of 2025 10 24 01:51:23 UT, corresponding to T-T0 = 17.04 hours.
We do not significantly detect the optical source identified by Mandarakas et al. (GCN 42404) at the 3-sigma upper limit of:
r’ < 21.78 mag (AB)
The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the magnitudes are not corrected for Galactic extinction. We used the STDWeb/STDPipe tools (Karpov 2025).
We acknowledge the excellent support from the Observatoire de Haute-Provence and in particular Jean Balcaen.