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GCN Circular 1047

SGR 1900+14, Chandra observations
2001-04-24T03:38:04Z (23 years ago)
Dale A. Frail at NRAO <>
D. W. Fox and D. L. Kaplan (Caltech) report on behalf of a larger

"In response to the 18 April 2001 flare of SGR 1900+14 (GCN 1041) the
Chandra X-ray Observatory has undertaken a sequence of two public
20-ksec observations of this source, on 22 and 30 April 2001.

The first observation began at 04:58 UT on 22 April and was taken in
continuous-clocking mode (see also GCN 1046).  Examination of the
light curve reveals that at least one burst was observed, 9081 s after
the start of the observation.  Assuming the best-fit spectral
parameters for the observation (see below), the peak 1-s flux of this
burst was of order 5e-10 erg cm^-2 s^-1 (0.5-10 keV).

Spectral fits to the full background-subtracted data set allow for at
least two emission models.  A power-law plus absorption model has
best-fit parameters of N_H = 3.18(2)e22 cm^-2, photon index alpha =
2.70(1), and unabsorbed 0.5-10 keV flux of 4.20(4)e-11 erg cm^-2 s^-1.
A power-law plus blackbody and absorption model has best-fit
parameters of N_H = 2.56(2)e22 cm^-2, photon index alpha = 1.88(1),
blackbody temperature kT = 0.532(3) keV, unabsorbed 0.5-10 keV flux of
2.17(3)e-11 erg cm^-2 s^-1, and flux fraction for the blackbody
component of 29% (0.5-10 keV).  The addition of the blackbody
component is not supported by an F-test (65% confidence level) but is
consistent with models in the literature (Perna et al. 2001,
astro-ph/0103273).  Analysis of the RXTE PCA data may help to clarify
the presence or absence of the blackbody component, as the PCA count
rates inferred from the two models given above differ by 50%.

No narrow spectral features are apparent.  The two-sigma upper limit
to the flux of a persistent 0.2-keV FWHM emission line in the 5-7 keV
range is 1e-5 photons cm^-2 s^-1.

This message may be cited."
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