[vsnet-grb-info 14333] GRB 131231A : xinglong TNT optical observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15647
SUBJECT: GRB 131231A : xinglong TNT optical observation
DATE:    14/01/01 13:10:54 GMT
FROM:    L.P. Xin at NAOC  <xlp at bao.ac.cn>

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

We began to observe GRB 131231A  (Sonbas et al., GCN 15640;
Xu et al., GCN 15641,15645; Malesani et al., GCN 15642; Singer et al. GCN 15643;
Halpern GCN 15646) with Xinglong 0.8-m TNT telescope at 10:29:40 (UT) , 
Jan. 1th, at 2014, about 29.73 hours after the burst.  
12*300 sec B,V,R-band images were obtained. 

The optical afterglow (Xu et al., GCN 15641)   was  clearly detected 
with a magnitude of 18.97+/-0.1 mag in R band, calibrated by USNO B1.0 R2mag 
at the mean time of 29.73 hours after the burst.

Compared with the report by Halpern GCN 15646, the brightness of this afterglow
decayed for 0.36 mag during the epoch between 22.55 hours and 29.73 hours after the burst.

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