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GCN Circular 2019

GRB030329: ROTSE network observes steepening of decay curve
2003-03-30T08:29:16Z (21 years ago)
Don Smith at U michigan <>
D. A. Smith reports on behalf of the ROTSE collaboration:

The ROTSE-IIIb instrument at McDonald Observatory in Texas began observing the
optical counterpart to GRB 030329 as soon as it was possible to do so.  The
first calibrated image began at 30 March 02:27:31 (UTC).  Images were
calibrated against the R-band magnitudes of the USNO A2.0 catalog, and the
source was initially found to be at an unfiltered magnitude of 15.35+-0.06 and
fading.  Analysis of the first 70 images showed clearly that the rate of decay
had increased when compared to the observations recorded by ROTSE-IIIa the
night before (Rykoff & Smith, GCN Circ. 1995).  Separate power-law fits to each
instrument's data set indicated that the flux decay slope had shifted from
about 1.0 (consistent with the decay slope reported by Price, et al. GCN
Circ. 2017) to about 1.9 (consistent with the decay reported by Garnavich et
al. GCN Circ. 2018).  A plot of these decay curves along with the power-law
fits can be seen at  An
extrapolation of these curves predicts a break time of about 12.1 h after the

ROTSE-IIIb will continue to observe GRB 030329 as long as it is able to do so.
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