GCN Circular 43208
Subject
GRB 251222A / EP251222b: LCO optical observations
Event
Date
2025-12-23T07:17:11Z (2 days ago)
Edited On
2025-12-23T16:20:28Z (a day ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
A. Saccardi, J. T. Palmerio (CEA/Irfu), C. Wu, L.P. Xin (NAOC), H. Yang, S. Guillot (IRAP) report on behalf of the SVOM mission team:
We observed the field of GRB 251222A (Yang et al., GCN 43188; Fermi GBM team, GCN 43186; Wang et al., GCN 43202; Guo et al., GCN 43201) with the LCO 1m telescope at South African Astronomical Observatory equipped with the Sinistro instrument.
Our observation started at 2025-12-22T19:31:31 (about 2.43 hr after the trigger) and we obtained 3x200 s exposures in the SDSS r and 3x200 s exposures in the Pan-STARRS z filters. The optical counterpart reported by Palmerio et al. (GCN 43189) is clearly detected in our images.
We measure the following magnitudes, calibrated against the Pan-STARRS1 catalog, and not corrected for Galactic extinction:
r = 18.55 +/- 0.01 AB (mid-time of 3.04 hr after the trigger);
z = 18.17 +/- 0.01 AB (mid-time of 2.59 hr after the trigger).
This result is consistent with the reports (An et al., GCN 43194; Durbak et al., GCN 43197, Li et al., GCN 43203).
This project is funded by the SVOM collaboration.