[vsnet-grb-info 5236] GRB 071013: TNT optical data refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6929
SUBJECT: GRB 071013: TNT optical data refined analysis
DATE:    07/10/17 15:08:04 GMT
FROM:    L.P. Xin at NAOC  <xlp at bao.ac.cn>

L.P. Xin, M. Zhai, Y.L. Qiu, J.Y. Wei, J.Y. Hu, J.S. Deng,
J.Wang and W.K. Zheng on behalf of EAFON report:


We refined the TNT data obtained in Oct. 13 (GCN 6908) 
the object observed by Kornienko et al. (GCN 6925) can 
not be confirmedin our R band images that were observed
in the same period.Our data was taken under bad seeing ~4".
In combined 6*60s R band image taken bewteen 12:39:03 - 
12:47:54 (UT), we could not see the object at the position 
RA(J2000)=18:37:49.1 Dec(J2000)=+33:50:25(Kornienko et al., GCN 6925).
The source of USNO-B1.0 1238-0299614(RA(J2000)=18:37:48.84  
Dec(J2000)= +33:50:26.7) was marginally detected in this combined 
image at 2.5 sigma level, and no obvious new object around was detected 
at the same sigma level. We examined images before 
and after this period, also no obvious new object was detected.

Using the same comparison star at RA (J2000) = 18:38:05.67, 
Dec (J2000) = +33:54:14.61 which has R2=17.22 (Kann et al., 
GCN 6917, GCN 6926),we estimate the USNO-B1.0 1238-0299614 star 
had the following magnitude at the epoch of our observation (GCN 6908):
---------------------------------------------------
T_start(UT)   T_stop(UT) Band  Exptime  Mag  M_err
12:21:38      12:38:45    R    13*60s   19.3 0.3
12:39:03      12:47:54    R    6*60s    19.4 0.4 
12:48:47      13:46:44    R    11*300s  19.7 0.2
---------------------------------------------------
We suggest the object reported in GCN6926 is the same star.

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