TITLE: GCN CIRCULAR NUMBER: 35824 SUBJECT: GRB 240225B: Liverpool Telescope afterglow observations DATE: 24/02/28 00:26:44 GMT FROM: Ben Gompertz at U of Birmingham <b.gompertz@bham.ac.uk> B. P. Gompertz (U. Birmingham), D. B. Malesani (DAWN/NBI and Radboud Univ.) report: We observed the position of the optical afterglow (Gompertz et al., GCN 35805; Liu et al., GCN 35812; Malesani et al., GCN 35819; Wise et al., GCN 35820) of GRB 240225B (Nakajima et al., GCN 35796; Joshi et al., GCN 35798; Kawakubo et al., GCN 35811) with the IO:O camera on the 2m robotic Liverpool Telescope (LT). Observations began at 21:37:18 on 2024-02-27, 2.06 days after trigger, and consisted of 15x120 s exposures in the SDSS r filter. We detect the afterglow with an AB magnitude of r = 20.04 +/- 0.05, calibrated against nearby SDSS stars and not corrected for foreground extinction. Between this epoch and the initial detection by GOTO (Gompertz et al., GCN 35805), the afterglow is well described by a power-law decay with an index of 0.8, which is consistent with the magnitudes reported by NOT (Malesani et al., GCN 35819) and LT (Wise et al., GCN 35820), though under-predicts those reported by Nanshan/HMT (Liu et al., GCN 35812), potentially suggestive of flaring behaviour at the time of their observation. The steepening in the light curve noted in GCN 35819 may be thus due to local variability, rather than a break in the power-law evolution. We note the presence of a faint underlying source at the afterglow position in Legacy Survey archival imaging, which may be the host galaxy of GRB 240225B. View this GCN Circular online at https://gcn.nasa.gov/circulars/35824. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...