TITLE:   GCN CIRCULAR
NUMBER:  43194
SUBJECT: GRB 251222A: NOT optical observations
DATE:    25/12/22 23:07:49 GMT
FROM:    Gregory Corcoran  at University College Dublin  <gregory.corcoran@ucdconnect.ie>

J. An (NAOC), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), B. Schneider (LAM), A. Saccardi (CEA/Irfu), L. Cotter (UCD), M. A. Diaz Teodori, A. Nitindala (University of Turku), report on behalf of a larger collaboration:

We observed the optical counterpart (Palmerio et al., GCN 43189) of GRB 251222A (Yang et al., GCN 43188; Fermi GBM team, GCN 43186) using the Nordic Optical Telescope equipped with the Standby Camera (StanCam). A series of 3 x 300s exposures were taken in the R band starting at 2025-12-22T21:34:54.

The afterglow is well detected in the individual images with an AB magnitude of R = 18.96 +/- 0.02 at a mid-time of 4.53 hr after the trigger. Our photometry was calibrated using nearby stars from the Pan-STARRS catalog and is not corrected for Galactic extinction.