GCN Circular 227
Subject
"GRB 990123: New BV Observations"
Date
1999-01-26T02:30:05Z (26 years ago)
From
Ram Sagar at UPSO <sagar@upso.ernet.in>
R.Sagar, A.K. Pandey, R.K.S. Yadav, Nilakshi and V. Mohan of U.P. State
Observatory, Manora Peak, Nainital, India report:
"We have observed the optical transient (GCN #201) of GRB
990123 (GCN #199) with the 104-cm telescope of the U.P. State Observatory,
Manora Peak, Nainital, India in Johnson B and Cousin R photometric
passband under good photometric sky conditions. We have calibrated the images
using photometric standards located in the field of open star cluster M67.
In each filter three images of 20 minutes are obtained and they are stcked to
improve signal to noise ratio of the optical transient.
We obtain the following magnitudes:
UT date filter mag err
Jan 24.90 R 21.25 0.1
Jan 24.99 B 22.05 0.2
The (B-R) colour of the OT becomes redder by about 0.2 mag compared to our
observations on Jan 23, 1999 (GCN #218).These results are preliminary
and more accurate results will be published later.
At the Web site http://www.rri.res.in/grb990123/ all the images taken
on the nights of Jan 23 and 24 are available. We have also taken
images during the night of 25/26 Jan 99 and will report the results later.
Sky conditions were good for photometric observations on the nights of
24/25 Jan 99 and 25/26 Jan 99 and we have observed the M67 field for
calibration purposes. Precise determination of the BVRI magnitudes of the stars
as well as of the OT in the field of the GRB990123 are in progress.
This message may be cited."