A. Pozanenko (IKI), A. Moiseev (SAO RAS), A. Moskvitin (SAO RAS), E.
Malygin (SAO RAS), S. Belkin (IKI, HSE), N. Pankov (IKI, HSE), V. Kim
(HSE, FAI) on behalf of GRB IKI FuN, A. Rossi (INAF-OAS), D. A. Kann
We observed the afterglow of GRB 211023A (Zhirkov et al, GCN 30977, see
also Kann et al, GCN 30982; Hu et al, GCN 30990; Belkin et al, GCN
31004; Vinko et al, GCN 31008; Belkin et al, GCN 31018; Belkin et al,
GCN 31020; Kumar et al, GCN 31023; Gupta et al., GCN 31041; Strobl et
al., GCN 31042) with BTA SAO RAS telescope equipped with SCORPIO-2
(VPHG940@600 grism). A total of 7200 s (6x1200 s) of spectra were
obtained starting on 21-11-05 (UT) 20:50:00, i.e. approximately 13.3016
days after burst. The afterglow is well detected in the acquisition
imaging with R = 21.61 +/- 0.04 (3 x 90 sec. 21-11-05 (UT) 20:43:59 --
20:50:58), and a continuum is visible across the bandwidth of a spectrum
4000 - 8500 A. The spectrum contain significant emission lines H_beta,
[OII] 3727, [OIII] 5007, at a common redshift of z=0.390. We assume
that the lines are from a host galaxy and, therefore, this is the
redshift of GRB 211023A. No evident lines of a possible SN were found.
Calibration of photometry is preliminary and based on nearby stars of
PS1 catalogue, gri -> R by Lupton transformations.
We are grateful to the directorate of SAO RAS for the TOO allocation.