GCN Circular 37995
Subject
GRB 241030B: BTA observations
Date
2024-10-31T00:19:17Z (a month ago)
From
Moskvitin Alexander at SAO RAS <mosk@sao.ru>
Via
legacy email
A. S. Moskvitin, A. S. Vinokurov (SAO RAS), A. S. Pozanenko (IKI),
N. Pankov (IKI, HSE) report on behalf of the GRB follow-up team.
We observed the field of GRB 241030B (Fermi GBM team, GCN 37980;
Klingler et al., GCN 37981; Evans, GCN 37983; Zhao et al., GCN 37984;
Evans et al., GCN 37992), with the 6-m telescope of SAO RAS equipped
with the focal reducer Scorpio-I. We obtained quasi-simultaneous
16 x 30 sec images both in B and Rc bands on October 30.
The OT (Fu et al., GCN 37985; Odeh et al., GCN 37986; Brivio et al.,
GCN 37991; Moskvitin t al., GCN 37987) is clearly detected in the Rc
stacked frame, but not presented in the B stacked frame:
UT_start--UT_end t_mid - T0, h filter OT_mag limit (3sigma)
20:17:39--20:43:25 1.9367 R 22.10 +/- 0.08 24.0
20:18:28--20:44:15 1.9504 B n/d 24.0
This preliminary photometry is based on nearby PS1 stars (magnitudes
converted with Lupton 2005 equations) and not corrected
for the Galaxy extinction.
We also obtained 2 x 1200 sec spectrum with VPHG550G grism
(3500--7500 AA, FWHM resolution ~ 10A) on October 30,
19:34:07--20:14:23 UT (T-mid - T0 = 1.3319 hours).
In the spectrum we do not find a continuum lower than 5200A.
Due to non-detection in B filter and absence of continuum
we conclude that redshift of the GRB z >~ 3.3.