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Title:
X-Ray Spectral Variations in the Youngest Galactic Supernova Remnant G1.9+0.3
Authors:
Reynolds, Stephen P.; Borkowski, Kazimierz J.; Green, David A.; Hwang, Una; Harrus, Ilana; Petre, Robert
Affiliation:
AA(Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA ), AB(Department of Physics, North Carolina State University, Raleigh, NC 27695-8202, USA ), AC(Cavendish Laboratory, 19 J.J. Thomson Avenue, Cambridge CB3 0HE, UK ), AD(NASA/GSFC, Code 660, Greenbelt, MD 20771, USA), AE(NASA/GSFC, Code 660, Greenbelt, MD 20771, USA), AF(NASA/GSFC, Code 660, Greenbelt, MD 20771, USA)
Publication:
The Astrophysical Journal Letters, Volume 695, Issue 2, pp. L149-L153 (2009). (ApJL Homepage)
Publication Date:
04/2009
Origin:
IOP
ApJ Keywords:
ISM: individual: G1.9+0.3, supernova remnants, X-rays: ISM
DOI:
10.1088/0004-637X/695/2/L149
Bibliographic Code:
2009ApJ...695L.149R

Abstract

The discovery of the youngest Galactic supernova remnant (SNR) G1.9+0.3 has allowed a look at a stage of SNR evolution never before observed. We analyze the 50 ks Chandra observation with particular regard to spectral variations. The very high column density (NH ~ 6 × 1022 cm-2) implies that dust scattering is important, and we use a simple scattering model in our spectral analysis. The integrated X-ray spectrum of G1.9+0.3 is well described by synchrotron emission from a power-law electron distribution with an exponential cutoff. Using our measured radio flux and including scattering effects, we find a rolloff frequency of 5.4(3.0, 10.2) × 1017 Hz (hνroll = 2.2 keV). Including scattering in a two-region model gives lower values of νroll by over a factor of 2. Dividing G1.9+0.3 into six regions, we find a systematic pattern in which spectra are hardest (highest νroll) in the bright southeast and northwest limbs of the shell. They steepen as one moves around the shell or into the interior. The extensions beyond the bright parts of the shell have the hardest spectra of all. We interpret the results in terms of dependence of shock acceleration properties on the obliquity angle θBn between the shock velocity and a fairly uniform upstream magnetic field. This interpretation probably requires a Type Ia event. If electron acceleration is limited by synchrotron losses, the spectral variations require obliquity-dependence of the acceleration rate independent of the magnetic-field strength.
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