GCN Circular 217

GRB 990123 Optical Follow-Up

J. Zhu, J. S. Chen, and H. T. Zhang, on behalf of the Beijing Astronomical
Observatory GRB team report:

"We observed the GRB 990123 OT (GCN #202) during Jan. 24.730-24.861 with
BAO 0.6-m Schmidt telescope under non-photometric weather. Combination of
two relatively best quality 60-min. images taken with BATC band-i filter
(central wavelength at 6660 A, band width 480 A) gives a detection of 
the object (OT+galaxy) at RA=15:25:30.17, Dec=+44:45:59.7 (J2000) with 
magnitude of 21.0 +/- 0.3 (Jan 24.818) using the No. 1 and No. 2 stars in
GCN #204. No visual seperation between OT and galaxy could be recognized
because of low S/N ratio and bad spatial resolution (1 pixel = 1.7",
seeing = 5.6"). Central 4' X 4' part of the whole 58' X 58' CCD field
will soon be available under 
http://vega.bac.pku.edu.cn/~zj/grb/grb990123.html

Re-reduction of GCN #204 observation with only first 2 of the 4 stars
gives same result for the OT+galaxy in magnitude of 19.2 +/- 0.1 (Jan
23.756).

This report may be cited."