TITLE:   GCN CIRCULAR
NUMBER:  11177
SUBJECT: GRB 100901A: Vega telescope optical afterglow observation
DATE:    10/09/02 14:40:47 GMT
FROM:    Drejc Kopac at Math Phys U,Slovenia  <drejc.kopac@fmf.uni-lj.si>

D. Kopac, B. Dintinjana and A. Gomboc (U. Ljubljana) report:

We observed the field of GRB 100901A (Immler et al., GCN 11159) with the
0.7m Vega telescope located in Ljubljana, starting at 20:31:31 UT on 2010
September 01, approx. 7 hours after the trigger. We took 10 images in R
band with exposure time 180s and we clearly detect the optical afterglow
(Guidorzi et al., GCN 11160). Our preliminary photometry yields

Mid time from    Filter   Magnitude
trigger (days)
-------------------------------------
0.302            R        17.2 +- 0.1
-------------------------------------

Magnitude is calibrated against the USNO-B1.0 1127-0027192 reference star
(R2=17.58) and is not corrected for Galactic extinction.