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GCN Circular 2027

GRB030328: X-ray Fading and Spectrum Measured with Chandra
2003-03-30T18:35:26Z (21 years ago)
George Ricker at MIT <>
GRB030328: X-ray Fading and Spectrum Measured with Chandra

P. G. Ford, N. R. Butler, H. L. Marshall, R. K. Vanderspek, G. R.
Ricker (MIT), J. G. Jernigan (U.C. Berkeley), and D. Q. Lamb (U. Chicago)


As reported in Butler et al. (GCN 2007), Chandra LETGS observations 
commenced on March 29.112 (t[burst] + 15.33 hr) of a field centered 
on the HETE WXM+SXC error region (Villasenor et al, GCN 1978) for 
GRB030328.  We report here on the first 39.7 ksec of data, which was 
taken until March 29.744 (t[burst] + 30.51 hr).  The relatively faint 
X-ray afterglow reported in GCN 2007 is observed to fade in 
brightness according to a power-law with a decay slope of -1.5 +/- 
0.3.  (This value is consistent with the decay slope value of -1.6 
found by Andersen et al. (GCN 1993) in the optical.)  The mean 
counting rate was 0.023 counts/s (summed over the dispersed signal 
from the LETGS, and including the 0th order flux).  The source 
spectrum, which we derive from our preliminary analysis of the 
dispersed LETGS counts, is characterized as follows:

nH = 4.32 x 10^20 cm^(-2), fixed at the Galactic value in the source direction;

dN/dE = A * E^ (-gamma) ph cm^(-2) s^(-1) keV^(-1) ,
over the 0.8-2.7 keV range, with A = 0.0001, and gamma = 1.80

Thus, the mean flux for the 0.8 to 2.7 keV band over the duration of
the Chandra observation was ~1.7 x 10^(-13) ergs cm^(-2) s^(-1).

Our analyses are continuing, and more detailed results will be posted at:

We thank Harvey Tananbaum for his generous allocation of Director's
Discretion Time to this observation, and the Chandra X-ray
Observatory Operations personnel for the impressive promptness with
which this observation was planned and carried out.

The preliminary results reported here may be cited.
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