TITLE: GCN CIRCULAR NUMBER: 37367 SUBJECT: GRB 240825A: TSHAO Optical Upper Limit DATE: 24/09/01 10:49:55 GMT FROM: Alexei Pozanenko at IKI, Moscow grb.alex@gmail.com
S. Belkin (HSE, IKI), I. Reva (FAI), A. Pozanenko (IKI), N. Pankov (HSE, IKI) report on behalf of the IKI GRB FuN:
We observed the field of Fermi GRB 240825A (Fermi GBM Team, GCN 37273; Gupta et al., GCN 37274; Di Lalla et al., GCN 37288; Kuin et al., GCN 37296; Joshi et al., GCN 37298; Sharma and Meegan, GCN 37301; Frederiks et al., GCN 37302; Laskar et al., GCN 37314) using the Zeiss-1000 telescope at Tien Shan Astronomical Observatory, starting on 2024-08-26 at 15:04:36 UT in the R filter. We did not detect the optical afterglow (Gupta et al., GCN 37274; Jiang et al., GCN 37275; Dutton et al., GCN 37276; Odeh and Guessoum, GCN 37277; Zhang et al., GCN 37278; Li et al., GCN 37280; Izzo et al., GCN 37287; Lipunov et al., GCN 37289; Leonini et al., GCN 37291; SVOM/C-GFT Team, GCN 37292; Martin-Carrillo et al., GCN 37293; Brivio et al., GCN 37295; Kuin et al., GCN 37296; Odeh and Guessoum, GCN 37299; Le Floc’h et al., GCN 37300; Guiffreda et al., GCN 37303; Zheng and Filippenko, GCN 37304; Wang et al., GCN 37306; Maksut et al., GCN 37307; Melandri et al., GCN 37310; Moskvitin et al., GCN 37313, 37336 ; Romanov GCN 37336; Qiu et al., GCN 37338; Freeburn et al., GCN 37361; ) at a redshift of z = 0.659 (Martin-Carrillo et al., GCN 37293; Melandri et al., GCN 37310).
Preliminary photometry is as follows: Date UT Start t-T0 (mid, days) Filter Exp. (s) OT Err. UL (3σ) 2024-08-26 15:04:36 0.98097 R 21x120 n/d n/d 21.3
The photometry was based on nearby USNO-B1.0 stars: RA DEC R2 22:58:26.6335 +01:01:11.863 14.45 22:58:14.8740 +00:55:48.392 13.57
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