TITLE: GCN CIRCULAR NUMBER: 42861 SUBJECT: GRB 251126A: Mondy and SAO RAS optical observations DATE: 25/11/27 13:38:15 GMT FROM: Alina Volnova at IKI RAS alinusss@gmail.com
A. Volnova (IKI), A. S. Moskvitin (SAO RAS), V. P. Goranskij (SAI MSU, SAO RAS), E. Klunko (ISTP), V. S. Shergin (SAO RAS), N. Pankov (HSE, IKI), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN:
We observed the field of the Swift GRB 251126A (Caputo et al., GCN 42843; Evans, GCN 42845; Goad et al., GCN 42851) with the AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy) in R-band and the Zeiss-1000 1m telescope of the SAO RAS in Rc-band on November 26/27 night. Observations with the AZT-33IK started at 20:35:11 UT (1.4097 hours after the trigger), observations with the Zeiss-1000 started at 21:31:39 UT (2.3508 hours after the trigger).
The optical afterglow (Swain, GCN 42844; Fu et al., GCN 42848; Reguitti et al., GCN 42849; Broens et al., GCN 42850; Anguloet al., GCN 42855; Pulido-Torres et al; GCN 42856; Gupta et al., GCN 42857; Cotter et al., GCN 42858; Seki et al, GCN 42859) is clearly detected in individual frames. Preliminary photometry is given below.
Date UT start t-T0 Exp. Filter OT Err. UL Seeing" Site/Instrum (mid,days) (n*s) (3sigma) 2025-11-26 20:35:11 0.06221 5*120 R 19.99 0.08 21.1 5.0 Mondy/AZT-33IK 2025-11-26 20:45:12 0.07125 8*120 R 19.84 0.07 21.4 5.0 Mondy/AZT-33IK 2025-11-26 21:01:12 0.08584 13*120 R 19.89 0.06 21.7 5.0 Mondy/AZT-33IK 2025-11-26 21:31:39 0.10164 2*300 Rc 19.81 0.08 21.2 2.2 SAO/Zeiss-1000 2025-11-26 21:58:22 0.12230 3*300 Rc 19.95 0.03 22.7 2.0 SAO/Zeiss-1000 2025-11-27 01:14:02 0.25960 2*600 Rc 20.63 0.04 23.2 1.6 SAO/Zeiss-1000 2025-11-27 01:57:56 0.29372 3*600 Rc 20.62 0.03 23.4 1.6 SAO/Zeiss-1000
The photometry is based on several nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction.
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