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).