TITLE:   GCN CIRCULAR
NUMBER:  37415
SUBJECT: GRB 240905E: CrAO Optical Afterglow observations, possible OT candidate
DATE:    24/09/06 16:02:02 GMT
FROM:    Alexei Pozanenko at IKI, Moscow <grb.alex@gmail.com>

S. Belkin (HSE, IKI), V. Rumyantsev (CrAO), A. Pozanenko (IKI), and N.
Pankov (HSE, IKI) report on behalf of the IKI GRB FuN:

We observed the field of GRB 240905E (Dichiara et al., GCN 37397) with the
ZTSh 2.6m telescope at the CrAO observatory starting on 2024-09-05 (UT) at
19:36:27. No optical source was detected in a Swift-XRT refined position
(Ferro et al., GCN 37406) up to R = 24.5. However, one source which is
absent in catalogues is near vicinity in XRT localization at coordinates of
(J2000) 23:03:13.149 +35:31:29.74 with uncertainty of 0.5 arcsec is
detected. The source is 5.5" away from the Swift-XRT Initial position
centre (Dichiara et al., GCN 37397) and 11.1" away from the Swift-XRT
refined position (Ferro et al., GCN 37406).

The preliminary photometry of the source is as follows:

Date UT Start t-T0 Filter Exp. OT err UL(3sigma)
(mid, days) (s)
2024-09-05 19:36:27 0.08778 R 6720 22.03 0.05 24.5

The photometry is based on nearby USNO-B1.0 (R2) stars:
RA DEC R2
23:03:16.6228872 +35:31:38.143092 15.84
23:03:10.2213480 +35:31:52.312872 17.59
23:03:23.1021888 +35:32:22.920108 15.81
23:03:10.8221064 +35:34:49.292328 16.04