Supernova Remnants: An Odyssey in Space after Stellar death

Supernova Remnants: An Odyssey in Space after Stellar death

Supernova Remnants: An Odyssey in Space after Stellar death


1st Abstract

Title (1st Abstract)

Stochastic acceleration and magnetic damping in Tycho's SNR

First Author

Alina Wilhelm


DESY Zeuthen

Additional Authors

Igor Telezhinsky
Vikram Dwarkadas
Martin Pohl

Presentation options



8. SNe and SNRs cosmic ray acceleration

1st Abstract

Tycho’s Supernova remnant (SNR) is also known as historical Supernova SN 1572 of Type Ia. Having exploded in a relatively clean environment and with a known age, it represents an ideal astrophysical testbed for the study of cosmic-ray acceleration and related phenomena. A number of studies suggest that shock acceleration with very efficient magnetic-field amplification is needed to explain the rather soft radio spectrum and the narrow rims observed in X-rays. We show that the wideband spectrum of Tycho’s SNR can be alternatively well explained when accounting for stochastic acceleration as a secondary process. The re-acceleration of particles in the turbulent region immediately downstream of the shock provided by the fast-mode waves is efficient enough to impact particle spectra over several decades in energy. Our self-consistent model contains hydrodynamic simulations of the SNR plasma flow. The particle spectra are obtained from the time-dependent transport equation and the background magnetic field is computed either from the induction equation or it follows analytic profiles depending on the considered model. Although not as efficient as standard diffusive shock acceleration, stochastic acceleration leaves its imprint on the particle spectra. This is especially notable in the emission at radio wavelengths and soft $gamma$-rays. Excessively strong magnetic fields and the so-called Alfv'{e}nic drift are not required in this scenario. The narrow X-ray and radio rims arise from damping of the turbulent magnetic field. We find a lower limit for the downstream magnetic field strength, $B_d = 173 , mathrm{mu G}$ and investigate the energy-dependence of the X-ray filament width. We conclude that stochastic re-acceleration is an important mechanism for modifying particle and emission spectra in SNR and that the magnetic-field damping should be taken into account to properly explain the synchrotron intensity profiles of Tycho.