TITLE:   GCN CIRCULAR
NUMBER:  36122
SUBJECT: GRB 240415A: SAO RAS optical observations
DATE:    24/04/15 21:04:13 GMT
FROM:    Moskvitin Alexander at SAO RAS <mosk@sao.ru>

A. Moskvitin, A. Vinokurov, A. Sarkisian (SAO RAS), N. Pankov (HSE, IKI),
A. Pozanenko (IKI), report on behalf of GRB follow-up team.

We observed the field of the GRB 240415A (Fermi GBM team, GCN 36107; Moss
et al., GCN 36108, Evans et al., GCN 36109) with the BTA, 6-m telescope of
SAO RAS, equipped with the Scorpio-2 multi-mode focal reducer (Afanasiev &
Moiseev,  2011, BaltA, 20, 363). We obtained series of 30 and 60 sec images
in VRI bands on April 15, 17:38:12--18:05:08 UT.

The OT (Pankov et al., GCNs 36118; 36121) is clearly detected in the
stacked frames of each band. Preliminary photometry of OT: R = 21.19 +/-
0.15 (17:39:08--18:03:53 UT, t_mid - T0 = 0.4754 days = 11.4104 hours). The
magnitudes were calibrated using R2 magnitudes of nearby USNO-B1.0 stars.