GCN Circular 904

GRB 001212 Optical Observation

J. Zhu, on behalf of the Beijing Astronomical Observatory GRB team, report:

"The approximately one degree square field centered with GRB 001212 error
box (Hurley et al., GCN 899
Not found
 
 
) was imaged again with the 0.6/0.9-m Schmidt
telescope (Zhu et al., GCN 903
Not found
 
 
) during Dec. 15.51-15.54, 15.69-15.76, and
Dec. 16.56-59 under good weather condition. Three 1200-s exposures 
(limiting magnitude for each is about R=21) and nine 600-s exposures were 
taken in Dec. 15 and three 960-s exposures in Dec. 16. The source 
mentioned by Mohan et al. (GCN 900
Not found
 
 
) was clearly detected in all images, 
and there seems to be no obvious variation at the level of photometric
accuracy (0.2-0.3 mag).

Using the following four USNO-A V1.0 objects (David Monet, et. al.)

================================
No.     RA (2000.0) Dec     mag.
--- ----------------------- ----
1   06:49:30.03 +36:24:35.5 14.6
2   06:49:31.16 +36:23:30.6 14.9
3   06:49:32.45 +36:22:12.1 14.3
4   06:49:32.63 +36:21:06.1 14.1
================================

as our magnitude references (the real procedure is to use R=14.475 for
the average magnitude of the above 4 stars), the magnitudes derived
from each frame are (combined with two previous images mentioned in
GCN 903
Not found
 
 
 for completeness; photometric error is one-sigma):

=============================
Date   mag  error    notes
----  ----- ----- -----------
14.63 17.66 1.52  bad weather
14.64 16.91 0.68  bad weather
15.51 18.69 0.14
15.53 18.72 0.14
15.54 18.39 0.13
15.69 18.39 0.18
15.70 18.60 0.22
15.71 18.97 0.28
15.72 18.55 0.19
15.73 18.82 0.26
15.73 18.64 0.22
15.74 19.20 0.37
15.75 18.71 0.24
15.76 18.64 0.23
16.56 18.84 0.16
16.58 18.58 0.14
16.59 18.57 0.17
=============================

We conclude that this object is not optical afterglow for GRB 001212."

This message may be cited.

-- 
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Jin Zhu                          | Tel.:  +86-10-62751286 (O)
Beijing Astronomical Observatory |        +86-314-5054767 (Schmidt dome)
Chinese Academy of Sciences      | Pager: +86-10-96301682333
P. R. China                      | Fax :  +86-10-62765031
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Room 2919, No. 2 Science Building, CAS-PKU Beijing Astrophysics Center,
Peking University, Beijing 100871, P. R. CHINA.
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email: zj@bac.pku.edu.cn                  http://vega.bac.pku.edu.cn/~zj
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