GCN Circular 84
Subject
GRB980519 optical observations
Event
Date
1998-05-21T09:17:17Z (28 years ago)
From
Jens Hjorth at NORDITA <jens@nordita.dk>
GRB 980519 Optical Observations
On behalf of the Nordic Optical Telescope GRB team J. Hjorth, A. O. Jaunsen,
K. Kjernsmo, and H. Pedersen report updated as well as new photometry of the
optical transient (Jaunsen et al., GCN #78) believed to be related to
GRB 980519.
As indicated by Djorgovski et al. (GCN #79) and Kemp & Halpern (GCN #80) the
photometry reported in GCN #78 was incorrect. This was due to the strongly
variable, non-photometric conditions prevailing at the time of observations.
Adopting the Kemp & Halpern (GCN #80) zero point the updated photometry of the
OT yields I=18.48+-0.1 on May 19.88 UT and I=19.05+-0.03 on May 20.00 UT.
In the same photometric system we report the following measurements:
May 20.98 UT I=21.64+-0.2
May 21.17 UT I=21.64+-0.1
These measurements are uncertain as the OT is close to the detection limit
in our images.
Thus, the rapid decay has continued during May 20 UT. Our last measurements
provide marginal evidence that the decay has leveled off. If confirmed, this
may be due to non-trivial intrinsic variability of the source or to an extra
source of light along the line of sight to the OT, eg. the host galaxy.
The above findings are preliminary. A more detailed analysis of the data
is in progress.
This note can be cited.