TITLE: GCN CIRCULAR NUMBER: 43183 SUBJECT: GRB 251221A: PRIME near-infrared observation DATE: 25/12/22 16:02:42 GMT FROM: N. Passaleva at Sapienza University of Rome <niccolo.passaleva@uniroma1.it> N. Passaleva (U Rome), O. Guiffreda (UMD), M. El Kabir (U Rome), J. Durbak (UMD), E. Troja (U Rome), A. S. Kutyrev (NASA/GSFC), S. B. Cenko (NASA/GSFC) Following the Fermi/Swift (Fermi GBM team, GCN 43164; Ambrosi et al., GCN 43166) detection, we observed the transient field in J and H filter with PRIME. Observations started ~15.5 hours after the initial trigger. Using Two Micron All Sky Survey (2MASS) nearby stars for preliminary calibration we detect an uncatalogued source at the position reported by Rakotondrainibe et al. (GCN 43168) and Volnova et al. (GCN 43180). We derived the following magnitudes not corrected for galactic extinction: J = 20.27 ± 0.09 H = 19.52 ± 0.04 PRIME is a 1.8m telescope with 1.56 square degree FOV (0.5 arcsec/pixel) located in Sutherland, South Africa at the South African Astronomical Observatory (SAAO) (Kutyrev et al. 2023, Yama et al. 2023, Durbak et al. 2024). We thank the Osaka University observers at PRIME and the staff at SAAO for their support with these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/43183. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...