TITLE: GCN CIRCULAR NUMBER: 43233 SUBJECT: GRB 251222A/EP251222b: FTW optical and NIR observations DATE: 25/12/24 14:24:34 GMT FROM: Malte Busmann at Ludwig-Maximilians-Universität München <m.busmann@physik.lmu.de> Malte Busmann (LMU), Xander J. Hall (CMU), Mitra Maleki (LMU), Brendan O'Connor (CMU), Daniel Gruen (LMU), and Antonella Palmese (CMU) report: We observed the counterpart of GRB 251222A/EP251222b (Fermi GBM team et al. GCN 43186, Yang et al. GCN 43188, Palmerio et al. GCN 43189, Guo et al. GCN 43201, Huang et al. GCN 43215) with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the r, i, and J-band simultaneously for 5 x 180 s starting at 2025-12-23T22:12:24 UT (1.21 days after the trigger). We detect the counterpart in all bands and measure an r-band magnitude of r = 20.68 +/- 0.02 AB mag. Our measurements are consistent with the reports by Lupinov et al. (GCN 43187), Palmerio et al. (GCN 43189), An et al. (GCN 43194), Calapai et al. (GCN 43195), Durbak et al. (GCN 43197), Li et al. (GCN 43203), Saccardi et al. (GCN 43204), Gupta et al. (GCN 43207), Saccardi et al. (CGN 43208), Kumar et al. (GCN 43209), Pérez-Fournon et al. (GCN 43212) Gupta et al. (GCN 43224), Glubus et al. (GCN 43225), Pankov et al. (GCN 43226), Freeberg et al. (GCN43229), and Volnova et al. (GCN 43230). The magnitude is calibrated against the PS1 catalog and not corrected for Galactic extinction. We thank Michael Schmidt from the Wendelstein Observatory for obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/43233. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...