TITLE:   GCN CIRCULAR
NUMBER:  10705
SUBJECT: GRB 100423A: xinglong TNT optical upper limit
DATE:    10/04/29 16:50:42 GMT
FROM:    L.P. Xin at NAOC  <xlp@bao.ac.cn>

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

We began to observe GRB100423A (Stroh et al., GCN 10651;
Filgas et al., GCN 10652; Ivarsen et al., GCN 10653) 
with Xinglong TNT telescope at 14:33:45(UT). The moon 
light was very bright. A series of R band images was 
obtained. No new source was found in the XRT errorbars 
within the combined 6*300s R band image. The 3 sigma upper 
limit is about 19.5 mag derived from USNO-B1.0,at the mean 
time of 14.2 hour after the burst.

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For more information about Xinglong GRBs Follow-up
observations, please visit the website:
http://www.xinglong-naoc.org/grb/