Gamma Ray Burst optical follow-up program
    C. Veillet (CFHT)  - M. Boer  (CESR)

GRB990123 observations

Go here for a detailed list of GRB990123 observations

The optical transient (OT) associated with the gamma ray burst GRB990123 has been observed with the new wide field camera CFH12k at the prime focus of the 3.6-m CFH Telescope on five consecutive nights by C. Veillet with the assistance of J. Anderson (University of Victoria, Canada) in the course of the French GRB follow-up program at CFHT (M. Boer, CESR, C. Veillet, CFHT).

Feb. 7 to 9   (posted on Feb. 18)

Three consecutive nights with image quality better than 1 arc-second allowed to better image the OT  area and also to obtain photometry in B, V and R of the OT and the surrouding galaxy.


Composite image of the field around the OT have been made in R (3 nights), B and V (one night). Using the star #18  published by Nilakshi et al. (GCN 252), the following magnitudes have been measured with the corresponding mean epoch:

R = 23.41 (0.1) on 1999 Feb 8.6  - 130 mn total integration time
V = 24.05 (0.15) on 1999 Feb 8.6  - 50 mn total integration time
B = 24.46 (0.15) on 1999 Feb 9.6  - 30 mn total integration time

Images of the OT area - galaxy resolved

As suspected from the first published image based on two poor seeing nights and one good night only, the galaxy is resolved clearly on the composite of the last three nights.

  The composite R image from Feb 7.6, 8.6 and 9.6

The contour map of the OT area (below - left) definitely shows the extended image of the surrounding galaxy, as a contour map of a nearby star of comparable magnitude (R=23.3) (below- right) a few arc-seconds apart does not exhibit any significant elongation.


GCN # 260   (1999 Feb 18)

Feb. 5 to 7


A composite image of the field around the OT has been made from eighteen 10mn exposures (six per night).  Using the standards published by Nilakshi et al. (GCN 252), the mean R magnitude of the OT averages to R = 23.45 (0.1) on 1999 Feb 6.6.

Images of the OT

Images of the field, with a detection limit of 25.0 (3 sigma), can be seen at the Web site . No object is detected in a radius of 5" centered on the

  A composite image of the OT

  The same image inverted (in gray)

  A close up on the OT area

GCN #253 (1999 Feb 8)