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GCN Circular 204

Subject
GRB990123 Optical Observation
Date
1999-01-23T22:44:31Z (25 years ago)
From
Jin Zhu at Beijing Obs <grb@bac.pku.edu.cn>
GRB 990123 Optical Observation

J. Zhu, H. T. Zhang, on behave of the Beijing Astronomical Observatory GRB 
team, report:

"R-band image of the BeppoSAX WFC error circle of GRB 990123 (Piro, GCN #199)
were obtained on 1999 Jan 23.756 UT, 8.5 hours after the GRB, with the BAO 
0.6/0.9m Schmidt telescope in Xinglong. The weather was bad, so only one
20-min. exposure image taken under thin cloud was usable (FWHM=6").

Central part of the image is posted at
http://vega.bac.pku.edu.cn/~zj/grb/grb990123.gif.

A faint object could be seen closed to the optical candidate position 
suggested by S. C. Odewahn et al. (GCN, #201). Its position from our 
measurement is RA=15:25:30.28, Dec=+44:45:59.0 (1 sigma = 0.5"), with 
magnitude of 19.2 (+/- 0.5 ?) if using the following 4 stars' magnitude 
information from the USNO-A V1.0 catalogue (David Monet, et. al.):

=========================================================
No. RA_mea (2000.0) Dec_mea  RA_cat (2000.0) Dec_cat mag.
--- -----------------------  ----------------------- ----
1   15:25:27.03 +44:46:23.3  15:25:27.04 +44:46:23.2 14.4
2   15:25:36.47 +44:44:37.6  15:25:36.45 +44:44:37.6 15.3
3   15:25:32.57 +44:44:29.9  15:25:32.66 +44:44:29.9 18.5
4   15:25:27.42 +44:44:42.5  15:25:27.48 +44:44:43.6 19.7
=========================================================

The object in our image seems slightly extended and slightly southwest
comparing with the discovery image of Odewahn et al., but it seems
to be impossible to confirm from only one image in not good quality.
However, it could be concluded that if such an object (in our image)
would not be real, the optical transient in Odewahn et al.'s images must 
be faded largely between the 4.6 hours interval.

This report may be cited."
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