TITLE:   GCN CIRCULAR
NUMBER:  11173
SUBJECT: GRB 100901A: THO optical observations
DATE:    10/09/02 08:55:23 GMT
FROM:    Veli-Pekka Hentunen at Taurus Hill Obs,A95  <veli-pekka.hentunen@kassiopeia.net>

Veli-Pekka Hentunen, Markku Nissinen and Tuomo Salmi (Taurus Hill
Observatory, Varkaus, Finland) report:

Taurus Hill Observatory (A95, Varkaus, Finland) C-14 telescope and SBIG
ST-8XME CCD camera were used to detect GRB 100901A optical afterglow.
The observations were started at 2010-09-01 21:08:30 (UT) and stopped at
2010-09-02 01:11:13 (UT). A number of unfiltered and BVR observations with
varying exposure times were made. The afterglow was detected at following
position RA 1 49 03.45 and DEC +22 45 30.5 consistent those given by Immler
s. et al. (GCN 11159) and Guidorzi C. et al. (GCN 11160) to within positional 
errors. 

The following magnitudes were obtained from the observations using USNO-B1.0
1127-0027231 (R = 15.37 and B = 16.38)) as the comparison:

+T0 (hour)     Filter         Exp (sec)     Mag     Mag err     Limit
7.606             unfiltered       2x120     17.1           0.1         18.4
7.678             unfiltered       2x120     17.2           0.2         18.5
10.607           unfiltered       3x300     17.3           0.1         19.6
11.141           Rc                3x300     17.4            0.1         20.0
11.228            B                 3x300     18.1            0.2         19.1
   

A jpg color image of the 4x300sec observations is available at the
following URL:

http://cutenews.kassiopeia.net/data/upimages/GRB100901A_LRGB_web_nuoli.jpg