TITLE: GCN CIRCULAR NUMBER: 40133 SUBJECT: GRB 250407A: Mondy and AbAO Optical Observations DATE: 25/04/10 09:17:26 GMT FROM: Nicolai Pankov at HSE, IKI RAS colinsergesen@gmail.com
N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP), R. Ya. Inasaridze (AbAO) report on behalf of IKI-GRB-FuN:
We observed the field of GRB 250407A detected by Fermi (the Fermi GBM team, GCN 40104; Preis & Greiner, GCN 40105; Mukherjee & Meegan, GCN 40114), SRG (Molkov et. al, GCN 40110), Swift (Evans, GCN 40111; Dichiara et. al, GCN 40113), EP (Zheng et. al, GCN 40119), Konus-Wind (Frederiks et. al, GCN 40121) with the 1.5-meter AZT-33IK telescope of the Sayan Solar Observatory (Mondy), and the 0.7-meter AS-32 telescope of the Abastumani Astrophysical Observatory (AbAO). The R-band observations began on 2025-04-08 at 18:01:15 UT, i.e. ~1.12 days since trigger at AbAO. The optical counterpart (Zheng & Fillipenko, GCN 40116; Ducoin et. al, GCN 40117; Pérez-Fournon et. al, GCN 40125) is marginally detected in the stacked image taken with AZT-33IK. The preliminary photometry is as follows:
Date UTstart Exptime t-T0 Filter OT Err UL Telescope (s) (mid, days) (3sigma) 2025-04-08 18:01:15 89*60 1.12319 R n/d n/d 17.5 AS-32 2025-04-09 14:42:55 34*120 1.97818 R 21.0 0.3 21.2 AZT-33IK
Ref. stars USNO-B1.0 RA Dec R2mag 110.81407 36.79950 15.86 110.78017 36.81867 14.55
The photometry is based on nearby USNO-B1.0 stars (R2 magnitudes) and has not been corrected for the Galactic extinction.
View this GCN Circular online at https://gcn.nasa.gov/circulars/40133. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...