X-Ray and Gamma-Ray Emission from Middle-aged Supernova Remnants in Cavities. I. Spherical Symmetry

Abstract

We present analytical and numerical studies of models of supernova-remnant (SNR) blast waves expanding into uniform media and interacting with a denser cavity wall, in one spatial dimension. We predict the nonthermal emission from such blast waves: synchrotron emission at radio and X-ray energies, and bremsstrahlung, inverse-Compton emission (from cosmic-microwave-background seed photons, ICCMB), and emission from the decay of ${\pi }^0$ mesons produced in inelastic collisions between accelerated ions and thermal gas, at GeV and TeV energies. Accelerated particle spectra are assumed to be power-laws with exponential cutoffs at energies limited by the remnant age or (for electrons, if lower) by radiative losses. We compare the results with those from homogeneous ("one-zone") models. Such models give fair representations of the 1-D results for uniform media, but cavity-wall interactions produce effects for which one-zone models are inadequate. We study the time evolution of SNR morphology and emission with time. Strong morphological differences exist between ICCMB and ${\pi }^0$-decay emission, at some stages, the TeV emission can be dominated by the former and the GeV by the latter, resulting in strong energy-dependence of morphology. Integrated gamma-ray spectra show apparent power-laws of slopes that vary with time, but do not indicate the energy distribution of a single population of particles. As observational capabilities at GeV and TeV energies improve, spatial inhomogeneity in SNRs will need to be accounted for.

References in corpus (6)

• Detection of the Characteristic Pion-Decay Signature in Supernova Remnants
• Observations of the young supernova remnant RX J1713.7-3946 with the Fermi Large Area Telescope
• Observations of the shell-type SNR Cassiopeia A at TeV energies with VERITAS
• Multi-dimensional models of circumstellar shells around evolved massive stars
• Hadronic versus leptonic origin of the gamma-ray emission from Supernova Remnant RX J1713.7-3946
• Models for Nonthermal Photon Spectra

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• Spatially Resolved Chandra Spectroscopy of the Large Magellanic Cloud Supernova Remnant N132D
• G279.0+1.1: a new extended source of high-energy gamma rays
• Revealing a new region of gamma-ray emission in the vicinity of HESS J1825-137