[vsnet-grb-info 15818] GRB 141121A: three epochs of SAO RAS optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17106
SUBJECT: GRB 141121A: three epochs of SAO RAS optical observations
DATE:    14/11/27 18:23:54 GMT
FROM:    Vladimir Sokolov at SAO RAS  <sokolov at sao.ru>

A.S. Moskvitin and V.N. Komarova report on behalf of a larger team:

We observed the field of GRB 141121A (Lien et al., GCN 17075)
with the SAO RAS 1-m Zeiss-1000 telescope at three nights:
2014.11.24/25, 25/26, 26/27.

The GRB OT (Tanga et al., GCN 17078) is clearly detected
in our stacked frames each night. Our charts can be found at
ftp://ftp.sao.ru/pub/grb/GRB141121A/GRB141121A_z1000_24_25_26.jpg

We used nearby SDSS stars for calibration. The "ugriz" magnitudes
were converted to "UBVRI" with the Lupon-2005 equations. Our OT
brightness measurements are in good agreement with R-band values
estimated within the close epochs and reported in the GCN circulars:
Kuroda et al. (GCN 17098), Mazaeva et al. (GCN 17102). Our OT
magnitudes are also similar to r-band measurements by Watson et al.
(GCN 17100) and Butler et al. (GCN 17101).
Our preliminary results are presented in the following table:
-----------------------------------------------------
Date   T-T0  UT_start-end Exp.,s  R_mag
-----------------------------------------------------
24.942 3.782 20:14--00:59  900 20.31+/-0.09
25.956 4.796 22:16--23:38 3600 20.86+/-0.04
26.980 5.820 22:12--00:50 4800 21.36+/-0.09
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