GCN Circular 1434
Subject
Fading Optical Source in the Field of GRB020531
Date
2002-06-20T02:49:35Z (23 years ago)
From
George Ricker at MIT <grr@space.mit.edu>
Fading Optical Source in the Field of GRB020531
A. Dullighan, G. Monnelly, N. Butler, R. Vanderspek, P. Ford, G.
Ricker (MIT); H. Ebeling, R. Wainscoat (U. Hawaii);
N. Kawai, A. Yoshida (RIKEN, Japan)
write:
We have observed the error box of the short-hard burst source
GRB020531 (GCN #1399, #1402) with the Baade 6.5m telescope
at the Magellan Observatory on June 1.16 and June 10.13 UT,
and with the Subaru 8.2m telescope at Mauna Kea Observatory
on June 5.43 UT. The R band images were calibrated using the
data provided by Henden et al.(GCN #1422). Our observations
were as follows:
2002 Date Instrument, Exposure Time Limiting R Mag.
UT Telescope (sec) (3 sigma)
June 1.16 LDSS2, Baade 180 23.6
June 5.43 SuprimeCam, Subaru 420 25.5
June 10.13 LDSS2, Baade 360 x 2 24.0
We detect a fading optical counterpart for Chandra Source #5
(GCN #1415) in all three epochs.
2002 Date R Mag Error
UT of #5
June 1.16 23.12 0.20
June 5.43 23.79 0.06
June 10.13 23.96 0.20
The decline in brightness of the counterpart between the measurements
is consistent with a power law decay with alpha = 0.35 +/- 0.05.
The relative X-ray brightness of Chandra Source #5 at the two
epochs of the Chandra observations is consistent with the optical
decay index. However, the independent significance of any X-ray
decline is low (1.4 sigma level-of-confidence).
Since Source #5 lies just outside the current error box for GRB020531
(GCN #1407), its possible association, if any, with GRB020531
is unclear.
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