X-ray Spectral Variations in the Youngest Galactic Supernova Remnant G1.9+0.3

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 ($N_H\sim 6\times 10^{22}$ 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 $5.4(3.0,10.2)\times 10^{17}$ Hz ($h{\nu }_{\mathrm{roll}}=2.2$ keV). Including scattering in a two-region model gives lower values of ν_roll 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 ν_roll) in the bright SE and NW 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 ${\theta }_{\mathrm{Bn}}$ 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.

5 pages, 2 figures; accepted for ApJ Letters

References in corpus (3)

• The Youngest Galactic Supernova Remnant: G1.9+0.3
• The radio expansion and brightening of the very young supernova remnant G1.9+0.3
• The X-ray Halo of GX5-1

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• Nonuniform Expansion of the Youngest Galactic Supernova Remnant G1.9+0.3
• Modeling SNR G1.9+0.3 as a Supernova Inside a Planetary Nebula
• TeV γ-ray observations of the young synchrotron-dominated SNRs G1.9+0.3 and G330.2+1.0 with H.E.S.S
• Expansion and Age of the X-ray Synchrotron-Dominated Supernova Remnant G330.2+1.0
• Type Ia Supernova Models: Asymmetric Remnants and Supernova Remnant G1.9+0.3
• Nonthermal properties of supernova remnant G1.9+0.3
• Magneto hydrodynamic simulations of the supernova remnant G1.9+0.3
• Brightening and Fading in the Youngest Galactic Supernova Remnant G1.9+0.3: 13 years of monitoring with the Chandra X-ray Observatory