GCN Circular 1346
Subject
GRB020331: Confirmation of Afterglow Candidate with Magellan
Date
2002-04-09T15:28:42Z (23 years ago)
From
George Ricker at MIT <grr@space.mit.edu>
GRB020331: Confirmation of Afterglow Candidate with Magellan
A. Dullighan, G. Monnelly, N. Butler, R. Vanderspek, G. Ricker (MIT)
write:
We obtained second epoch observations of the HETE error circle of
GRB020331 (Ricker et al., GCN #1315) with the Baade 6.5m telescope at
Magellan on 2002 April 9.06 UT using LDSS-2. The observations took
place 8.37 days after the burst, and 7.84 days after our first epoch
observations (Monnelly et al., GCN #1339). Two 200s R-band exposures
were used to image a 7.5 arcmin diameter region centered on the
coordinates of the afterglow candidate first reported by Fox et. al.
(GCN #1334).
In our second epoch observations, we detect the afterglow candidate
at R = 22.9 +/- 0.14. In comparison to our first epoch measurement,
with exactly the same instrument configuration, the afterglow
candidate has declined by 1.8 +/- 0.2 magnitudes in R. As in our
first epoch observations, magnitudes are calibrated against star
G020331 (R = 18.945) from the photometry of Henden et. al. (GCN
#1319).
Combining our first and second epoch observations, the power law
decay index of the afterglow candidate is well-determined as alpha =
0.62 +/- 0.1. We conclude that the Fox et al candidate is indeed the
optical afterglow of GRB020331.
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