TITLE:   GCN CIRCULAR
NUMBER:  38732
SUBJECT: GRB 241229B: CrAO ZTSh possible optical counterpart of SVOM/VT confirmation
DATE:    24/12/30 20:16:39 GMT
FROM:    Alexei Pozanenko at IKI, Moscow <grb.alex@gmail.com>

A. Volnova (IKI), A. Pozanenko (IKI), V. Rumyantsev (CrAO), N. Pankov (HSE,
IKI) report on behalf of GRB-IKI-FuN collaboration:

We observed the GRB 241229B (Fermi GBM Team, GCN 38698; D'Ai et al., GCN
38699) with 2.6-meter ZTSh telescope of CrAO. The observations started on
2024-12-29 (UT) 20:22:02, i.e. ~15.4 hours after GBM trigger.

We clearly detected SVOM/VT optical candidate (SVOM/VT team, GCN 38729).
The preliminary photometry of the the optical candidate is the following:

Date UT start T0+ Exp. Filter OT Err. UL(3sigma)
(mid, days) (s)

2024-12-29 20:22:02 0.64631 88x120 R 21.91 0.05 24.2

The magnitudes are calibrated using nearby Pan-Starrs PS1 (transformed into
R by Lupton's transformations)

RA Dec R_Lupton
18:16:50.10 +74:41:42.2 18.928 +- 0.020
18:16:33.99 +74:41:43.6 18.778 +- 0.026
18:16:26.64 +74:41:33.2 17.917 +- 0.014