TITLE:   GCN CIRCULAR
NUMBER:  11065
SUBJECT: GRB 100805A: Xinglong TNT optical observation
DATE:    10/08/06 05:36:45 GMT
FROM:    L.P. Xin at NAOC  <xlp@bao.ac.cn>

L.P. Xin, Z. X. Ling, Y.L. Qiu, J.Y. Wei, J. Wang, J.S. Deng, 
C. Wu, X. H. Han, J.Y. Hu on behalf of EAFON report:

We began to observe GRB100805A (Hoversten E. A. et al., GCN 11047 ) 
with Xinglong TNT telescope at 12:29:52 (UT), 8.28h after 
the burst. Nine R band images were obtained. The exposure time for
each frame is 600 sec. The afterglow (Hoversten E. A. et al., GCN 11047)
with a brightness of 21.3+/-0.2 mag was detected with the combined 
9*600s white-band data at the mean time of 8.95h after the burst.

The reference star is a nearby USNO-B1.0 star with a coordinates 
of 19:59:33.3, +52:37:54.0, and a brightness of R2=17.41 mag.

Combining TNT data and other data reported in the previous GCN circulars 
(Cenko, GCN 11050, GCN 11051;Gomboc et al. GCN11052; 
Nissinen et al. GCN 11056; Gorosabel et al. GCN 11060; Wren et al. GCN 11064 ), 
we infer that the brightness of OT was decaying with a power-law decay index of 
alpha~0.73 from 100sec to 8.9h after the burst, consistent with 
the reports of  Cenko, GCN Circ. 11051 and  Gomboc  et al. GCN 10052.


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