K. M. Schure

Cosmic ray acceleration and escape from supernova remnants

Galactic cosmic ray (CR) acceleration to the knee in the spectrum at a few PeV is only possible if the magnetic field ahead of a supernova remnant (SNR) shock is strongly amplified by CR escaping the SNR. A model formulated in terms of the electric charge carried by escaping CR predicts the maximum CR energy and the energy spectrum of CR released into the surrounding medium. We find that historical SNR such as Cas A, Tycho and Kepler may be expanding too slowly to accelerate CR to the knee at the present time.

The imprint of a symbiotic binary progenitor on the properties of Kepler's supernova remnant

We present a model for the type Ia supernova remnant (SNR) of SN 1604, also known as Kepler’s SNR. We find that its main features can be explained by a progenitor model of a symbiotic binary consisting of a white dwarf and an AGB donor star with an initial mass of 4−5 M� . The slow, nitrogen-rich wind emanating from the donor star has partially been accreted by the white dwarf, but has also created a circumstellar bubble. On the basis of observational evidence, we assume that the system moves with a velocity of 250 km s −1 . Owing to the spatial velocity, the interaction between the wind and the interstellar medium has resulted in the formation of a bow shock, which can explain the presence of a one-sided, nitrogen-rich shell. We present two-dimensional hydrodynamical simulations of both the shell formation and the SNR evolution. The SNR simulations show good agreement with the observed kinematic and morphological properties of Kepler’s SNR. In particular, the model reproduces the observed expansion parameters (m = V/(R/t)) of m ≈ 0.35 in the north and m ≈ 0.6 in the south of Kepler’s SNR. We discuss the variations among our hydrodynamical simulations in light of the observations, and show that part of the blast wave may have completely traversed through the one-sided shell. The simulations suggest a distance to Kepler’s SNR of 6 kpc, or otherwise imply that SN 1604 was a sub-energetic type Ia explosion. Finally, we discuss the possible implications of our model for type Ia supernovae and their remnants in general.

Modelling the interaction of thermonuclear supernova remnants with circumstellar structures: the case of Tycho's supernova remnant

The well-established Type Ia remnant of Tychos supernova (SN 1572) reveals discrepant ambient medium-density estimates based on either the measured dynamics or the X-ray emission properties. This discrepancy can potentially be solved by assuming that the supernova remnant (SNR) shock initially moved through a stellar wind bubble, but is currently evolving in the uniform interstellar medium with a relatively low density. We investigate this scenario by combining hydrodynamical simulations of the wind-loss phase and the SNR evolution with a coupled X-ray emission model, which includes non-equilibrium ionization. For the explosion models we use the well-known W7 deflagration model and the delayed detonation model that was previously shown to provide good fits to the X-ray emission of Tychos SNR. Our simulations confirm that a uniform ambient density cannot simultaneously reproduce the dynamical and X-ray emission properties of Tycho. In contrast, models that considered that the remnant was evolving in a dense, but small, wind bubble reproduce reasonably well both the measured X-ray emission spectrum and the expansion parameter of Tychos SNR. Finally, we discuss possible mass-loss scenarios in the context of single- and double-degenerate models which possibly could form such a small dense wind bubble.

From cosmic ray source to the Galactic pool

The Galactic cosmic ray spectrum is a remarkably straight power law. Our current understanding is that the dominant sources that accelerate cosmic rays up to the knee (

Progenitor's signatures in Type Ia supernova remnants

3 \times 10^{15}

Evolution of magnetic fields in supernova remnants

eV) or perhaps even the ankle (

ERRATUM: “THE RELATION BETWEEN POST-SHOCK TEMPERATURE, COSMIC-RAY PRESSURE, AND COSMIC-RAY ESCAPE FOR NON-RELATIVISTIC SHOCKS” (2010, ApJ, 722, 1727)

3 \times 10^{18}

Spectra and energies of cosmic rays in young supernova remnants

eV), are young Galactic supernova remnants. In theory, however, there are various reasons why the spectrum may be different for different sources, and may not even be a power law if nonlinear shock acceleration applies during the most efficient stages of acceleration. We show how the spectrum at the accelerator translates to the spectrum that make up the escaping cosmic rays that replenish the Galactic pool of cosmic rays. We assume that cosmic ray confinement, and thus escape, is linked to the level of magnetic field amplification, and that the magnetic field is amplified by streaming cosmic rays according to the non-resonant hybrid or resonant instability. When a fixed fraction of the energy is transferred to cosmic rays, it turns out that a source spectrum that is flatter than

What Does The Jet Of Cas A Tell Us About Its Progenitor Star? Hydrodynamics Inc.

E^{-2}

Connection of interchange instabilities in tokamaks and Parker instabilities in spiral arms of galaxies

will result in a