GCN Circular 37244

 S. Belkin (HSE, IKI), N. Pankov (HSE, IKI), E. Klunko (ISTP), R. Ya.
Inasaridze (AbAO), A. Pozanenko (IKI) report on behalf of GRB-IKI-FuN:

We observed the field of GRB 240809A, detected by Swift (Evans et al., GCN
37110
Not found
 
 
) and SVOM (Wang et al., GCN 37113
Not found
 
 
), using the AZT-33IK 1.5-meter
telescope at the Sayan Observatory (Mondy) and the AS-32 0.7-meter
telescope at the Abastumani Observatory (AbAO). The observations began on
2024-08-09 at 13:54:52 (UT) and 17:27:38 (UT), respectively, i.e., about
0.2 and 7 hours after the Swift trigger. The preliminary photometry of the
optical counterpart (Evans et al., GCN 37110
Not found
 
 
; Dubay et al., GCN 37114
Not found
 
 
;
Jiang et al., GCN 37116
Not found
 
 
; Gottumukkala et al., GCN 37122
Not found
 
 
; Shilling et al.,
GCN 37123
Not found
 
 
; Mohan et al., GCN 37125
Not found
 
 
; Zheng & Filippenko, GCN 37127
Not found
 
 
;
Schneider et al., GCN 37129
Not found
 
 
; Quadri et al., GCN 37131
Not found
 
 
; Brivio et al., GCN
37132
Not found
 
 
; Midavaine et al., GCN 37159
Not found
 
 
; Ruocco et al., GCN 37194
Not found
 
 
) is provided
below:

Date UT Start t-T0 Exp. Filter OT Err. UL Telescope
(mid, days) (s) (3sigma)
2024-08-09 13:54:52 0.24228 49*60 R 19.45 0.05 22.3 AZT-33IK
2024-08-09 17:27:38 0.37302 44*60 R n/d n/d 20.0 AS-32

The magnitudes were calibrated using nearby comparison stars from the
USNO-B1.0 catalog (R2 magnitudes). No correction was made for the Galactic
extinction toward the GRB, corresponding to E(B-V) = 0.213 (S&F 2011). The
optical light curve is well fitted by a power-law model with an index of
-1.3, which is typical for GRBs.