TITLE: GCN CIRCULAR NUMBER: 40653 SUBJECT: GRB 250527C: CrAO Optical Upper Limit DATE: 25/06/09 10:19:33 GMT FROM: Nicolai Pankov at HSE, IKI RAS colinsergesen@gmail.com
N. Pankov (HSE, IKI), S. Nazarov (CrAO), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN:
We observed the field of GRB 250527C detected by Fermi/GBM (Trigger 770047117) and further localized by Swift/BAT-GUANO (Delaunay et. al, GCN 40563). The field has also been observed by Swift/XRT (Evans, GCN 40564), and Swift/UVOT (Klingler, GCN 40574). Our observations were carried out using the Sintez-Newton 0.36-meter telescope installed at the Crimean Astrophysical Observatory (CrAO). The series of images has taken in the R-filter. We do not detect candidate transients in comparison with USNO-B1.0, and PS1 catalogs in the stacked image of 22*120 sec. Particularly, we were searching for candidates inside localization circles of X-Ray sources provided in (Evans, GCN 40564). The preliminary upper limit is given below:
Date UTstart T-T0 Exposure Filter OT Err UL (n*T) (3-sigma) 2025-05-28 23:46:57 1.42390 22*120 R n/d n/d 19.1
The photometry was calibrated using nearby USNO-B1.0 stars (R2 magnitudes) and has not been corrected for the Galactic extinction.
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