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GCN Circular 1992

Subject
GRB030328: Decay index
Date
2003-03-29T15:48:00Z (21 years ago)
From
Michael I. Andersen at Astrophys.Inst.Potsdam <mandersen@aip.de>
M. I. Andersen (Astrophysikalisches Institut Potsdam)
G. Masi (University of Rome "Tor Vergata" and European Southern Observatory,
Chile), B. L. Jensen and J. Hjorth (Copenhagen University) report:


We have obtained R-band observations of the afterglow of GRB030328,
initially reported by Peterson & Price (GCN 1974), using the Danish 1.54m
telescope (La Silla) + DFOSC. Using the zero point reported by Fugazza et al.
(GCN 1982) (star B=16.31) a preliminary analysis gives

Mar. 29, 02:59 UT   20.91 +/- 0.09
Mar. 29, 03:12 UT   20.73 +/- 0.07
Mar. 29, 03:34 UT   21.00 +/- 0.09
Mar. 29, 03:54 UT   20.85 +/- 0.06
Mar. 29, 04:15 UT   21.00 +/- 0.07
Mar. 29, 04:42 UT   20.95 +/- 0.07
Mar. 29, 05:21 UT   21.10 +/- 0.07
Mar. 29, 05:53 UT   21.03 +/- 0.07
Mar. 29, 07:17 UT   21.23 +/- 0.10
Mar. 29, 07:46 UT   21.36 +/- 0.11

A fit to this data set gives a decay index of alpha = 1.6 +/- 0.3.
If the two last data points are ignored and the two data points
from Fugazza et al. are included, a decay index of alpha = 1.2 +/- 0.2
is derived. This is consistent with the early decay index of
alpha = 1.0 +/- 0.1 reported by Price and Peterson (GCN 1977) and
may indicate that the light curve encountered a break around t=0.8 days.

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