TITLE: GCN CIRCULAR NUMBER: 39083 SUBJECT: GRB 250127A: CrAO and Terskol optical upper limits DATE: 25/01/29 13:11:18 GMT FROM: Nicolai Pankov at HSE, IKI RAS colinsergesen@gmail.com
N. Pankov (HSE, IKI), A. Pozanenko (IKI), V. Rumyantsev (CrAO), I. Sokolov (INASAN) report on behalf of the IKI-GRB-FuN:
We performed optical observations of the field of GRB 250127A (Wu et. al, GCN 39041; Turpin et. al, GCN 39043; Evans, GCN 39044; Xin et. al, GCN 39047; Yin et. al, GCN 39053; Kennea et. al, GCN 39056) in the R-filter using the 2.6-meter ZTSh telescope of the Crimean Astrophysical Observatory (CrAO), and in Clear light with the 0.8-meter K-800 telescope of the Terskol Observatory (INASAN). The observations began on 2025-01-27 23:27 UT, i.e. ~0.022 days since SVOM trigger. We do not detect any new sources spatially consistent with the X-Ray afterglow position reported by the Swift XRT team (Kennea et. al, GCN 39056) and the EP-FXT team (Yin et. al, GCN 39053). The preliminary upper limits are given below:
Date UT start t-T0 Exp. Filter UL(3sigma) Telescope (mid, days) (s) 2025-01-27 23:27:51 0.02251 87*30 Clear 18.2 K-800 2025-01-28 00:08:00 0.80364 14*120 R 23.7 ZTSh
The photometry has calibrated using nearby stars from the USNO-B1.0 catalog (R2 magnitudes). No correction has been made for the Galactic extinction A_R = 0.119 (Schlegel & Finkbeiner, 1998).
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