The composite R image from Feb 7.6, 8.6 and 9.6
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.
Photometry
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.
Photometry
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 http://www.cfht.hawaii.edu/~veillet/grb990123.html
. No object is detected in a radius of 5" centered on the
OT.
A composite image of the OT
The same image inverted (in gray)
A close up on the OT area