TITLE:   GCN CIRCULAR
NUMBER:  38542
SUBJECT: GRB 241207A: TSHAO Zeiss-1000 optical observations
DATE:    24/12/12 14:19:10 GMT
FROM:    Nicolai Pankov at HSE, IKI RAS <colinsergesen@gmail.com>

N. Pankov (HSE, IKI), I. Reva (FAI), M. Krugov (FAI), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN:

We performed optical observations of GRB 241207A (Fermi GBM team, GCN 38454; V.Lipunov et. al, GCN 38459; McKenna et. al, GCN 38536) in the R filter with 1-meter Zeiss-1000 telescope of Tien-Shan observatory (TSHAO). The observations began on 2024-12-07 13:04:43 UT, i.e. ~0.17 days since trigger. Using STDWeb (Karpov, 2024) ZOGY-based image subtraction against ZTF DR7 we did not find an optical candidate transient in the median stacked images of the fields:

FieldID RA       Dec       Width Height
        (hr)     (deg)       (arcmin)
1       19:15:05 +42:01:05 19.03 19.03
2       19:09:58 +42:29:55 19.03 19.03

The preliminary upper limits are as follows:

Date       UT start  t-T0         Exp.    Filter   OT  Err. UL(3sigma) FieldID
                     (mid, days)  (s)
2024-12-07 13:04:43  0.176087     4*90    R        n/d n/d  20.3       1
2024-12-07 13:15:56  0.206782     48*90   R        n/d n/d  20.8       2


The magnitudes were calibrated using nearby stars from USNO-B1.0 (R2 magnitudes) and are not corrected for the Galactic extinction towards the GRB 241207A.