Synchrotron X-ray diagnostics of cutoff shape of nonthermal electron spectrum at young supernova remnants

Abstract

Synchrotron X-rays can be a useful tool to investigate electron acceleration at young supernova remnants (SNRs). At present, since the magnetic field configuration around the shocks of SNRs is uncertain, it is not clear whether electron acceleration is limited by SNR age, synchrotron cooling, or even escape from the acceleration region. We study whether the acceleration mechanism can be constrained by the cutoff shape of the electron spectrum around the maximum energy. We derive analytical formulae of the cutoff shape in each case where the maximum electron energy is determined by SNR age, synchrotron cooling and escape from the shock. They are related to the energy dependence of the electron diffusion coefficient. Next, we discuss whether information on the cutoff shape can be provided by observations in the near future which will simply give the photon indices and the flux ratios in the soft and hard X-ray bands. We find that if the power-law index of the electron spectrum is independently determined by other observations, then we can constrain the cutoff shape by comparing theoretical predictions of the photon indices and/or the flux ratios with observed data which will be measured by NuSTAR and/or ASTRO-H. Such study is helpful in understanding the acceleration mechanism. In particular, it will supply another independent constraint on the magnetic field strength around the shocks of SNRs.

15 pages, 6 figures

References in corpus (11)

• The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission
• The 70 Month Swift-BAT All-Sky Hard X-Ray Survey
• Analytical solutions for energy spectra of electrons accelerated by nonrelativistic shock-waves in shell type supernova remnants
• Observations of the young supernova remnant RX J1713.7-3946 with the Fermi Large Area Telescope
• Study of Nonthermal Emission from SNR RX J1713.7-3946 with Suzaku
• Fast Variability of Nonthermal X-Ray Emission in Cassiopeia A: Probing Electron Acceleration in Reverse-Shocked Ejecta
• In which shell-type SNRs should we look for gamma-rays and neutrinos from p-p collisions?
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• Suzaku observations of the hard X-ray spectrum of Vela Jr
• Fast Particle Acceleration at Perpendicular Shocks with Uniform Upstream Magnetic Field and Strong Downstream Turbulence
• Secondary Production as the Origin for the Cosmic Ray Positron Excess
• Particle acceleration controlled by ambient density in the southwestern rim of RCW 86
• Detection of the hard X-ray non-thermal emission from Kepler's supernova remnant
• The Fermi bubbles as a Superbubble
• Search for the time evolution of the synchrotron X-ray spectrum of the youngest Galactic supernova remnant G1.9+0.3 using Suzaku