TITLE:   GCN CIRCULAR
NUMBER:  39114
SUBJECT: GRB 250129A: Liverpool Telescope observations suggest continued engine activity
DATE:    25/02/01 13:22:21 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), R. Brivio (INAF-OAB) and A. J. Levan (Radboud) report on behalf of a larger collaboration:

We initiated follow-up observations of GRB 250129A (Beardmore et al., GCN 39066) with the IO:O camera on the 2m robotic Liverpool Telescope (LT). Observations were taken across the nights of 2025-01-30 and 2025-01-31, consisting of 5x180 s exposures in each of the SDSS r and i filters. In a preliminary analysis, we measure the following AB magnitudes:

t-t0(d)  exp(s)  filt        mag     error
2.06     900      r           20.29   0.04
2.93     900      r           20.40   0.05

Magnitudes are calibrated against nearby Pan-STARRS stars and are not corrected for galactic extinction.

Our measurements indicate either minimal evolution between 2 and 3 days after trigger, or a continuation of the flaring behaviour observed during the first 24 hours, as noted by Belkin et al. (GCN 39072), Francile et al. (GCN 39075), Brivio et al. (GCN 39079), Zheng & Filippenko (GCN 39090), Antier et al. (GCN 39096), and Malesani et al. (GCN 39100).