TITLE: GCN CIRCULAR NUMBER: 37072 SUBJECT: GRB 240805B: AbAO, CrAO, and Terskol optical upper limits DATE: 24/08/06 14:20:22 GMT FROM: Alexei Pozanenko at IKI, Moscow <grb.alex@gmail.com> N. Pankov (HSE, IKI), A. Pozanenko (IKI), V. Rumyantsev (CrAO), R. Ya. Inasaridze (AbAO), A. Shikherin (KIAM) report on behalf of GRB-IKI-FuN: We observed the field of GRB 240805B detected by Swift (Williams et al, GCN 37043; Goad et al, GCN 37053) with AS-32 0.7-meter telescope of Abastumani observatory (AbAO) in R-filter, ZTSh 2.6-meter telescope of CrAO in R-filter, and K800 0.8-meter telescope of Terskol observatory in clear filter. The observations began on 2024-08-05 at 17:30 UT at AbAO (i.e. 3.1 hr since Swift trigger) in variable conditions. We obtain upper limits on the optical counterpart found and confirmed in (Moskvitin et al, GCN 37055; Du et al, GCN 37062): Date UT start t-T0 Exp. Filter OT Err. UL Observ./Scope (mid, days) (s) (3-sigma) 2024-08-05 17:30:52 0.14442 52x60 R n/d n/d 20.2 AbAO/AS-32 2024-08-05 19:50:58 0.24449 30*120 R n/d n/d 20.5 CrAO/ZTSh 2024-08-05 20:10:07 0.23695 44*30 CR n/d n/d 17.0 Terskol/K800 The photometry was calibrated against nearby stars of USNO-B1.0 (R2 magnitudes). The upper limits are in agreement with no detections by (Zhu et al, GCN 37050; Strausbaugh et al, GCN 37052; Siegel & Williams, GCN 37057; Maksut et al, GCN 37060). View this GCN Circular online at https://gcn.nasa.gov/circulars/37072. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...