Efficiencies of Magnetic-Field Amplification and Electron Acceleration in Young Supernova Remnants: Global Averages and Kepler's Supernova Remnant

Abstract

Particle acceleration to suprathermal energies in strong astrophysical shock waves is a widespread phenomenon, generally explained by diffusive shock acceleration. Such shocks can also amplify upstream magnetic field considerably beyond simple compression. The complex plasma physics processes involved are often parameterized by assuming that shocks put some fraction ${\epsilon }_e$ of their energy into fast particles, and another fraction ${\epsilon }_B$ into magnetic field. Modelers of shocks in supernovae, supernova remnants, and gamma-ray bursters, among other locations, often assume typical values for these fractions, presumed to remain constant in time. However, it is rare that enough properties of a source are independently constrained that values of the epsilons can be inferred directly. Supernova remnants (SNRs) can provide such circumstances. Here we summarize results from global fits to spatially integrated emission in six young SNRs, finding $10^{-4}\le {\epsilon }_e\le 0.05$ and $0.001\le {\epsilon }_B\le 0.1$. These large variations might be put down to the differing ages and environments of these SNRs, so we conduct a detailed analysis of a single remnant, that of Kepler's supernova. Both epsilons can be determined at seven different locations around the shock, and we find even larger ranges for both epsilons, as well as for their ratio (thus independent of the shock energy itself). We conclude that unknown factors have a large influence on the efficiency of both processes. Shock obliquity, upstream neutral fraction, or other possibilities need to be explored, while calculations assuming fixed values of the epsilons should be regarded as provisional.

arXiv comment16 pages, 7 figures; accepted for publication in ApJ

References in corpus (36)

• Spectra and Light Curves of Gamma-Ray Burst Afterglows
• On the magnetic fields and particle acceleration in Cas A
• Magnetic Field Amplification in Tycho and other Shell-type Supernova Remnants
• Fine Structures of Shock of SN 1006 with the Chandra Observation
• Fundamental Physical Parameters of Collimated Gamma-Ray Burst Afterglows
• A revised catalogue of 294 Galactic supernova remnants
• Observational constraints on energetic particle diffusion in young SNRs: amplified magnetic field and maximum energy
• The Youngest Galactic Supernova Remnant: G1.9+0.3
• Radio Emission and Particle Acceleration in SN 1993J
• A Deep Chandra Observation of Kepler's Supernova Remnant: A Type Ia Event with Circumstellar Interaction
• Electron Injection by Whistler Waves in Non-relativistic Shocks
• Cassiopeia A and its Clumpy Presupernova Wind
• RCW 86: A Type Ia Supernova in a Wind-Blown Bubble
• Spitzer Space Telescope Observations of Kepler's Supernova Remnant: A Detailed Look at the Circumstellar Dust Component
• Dust Destruction in Fast Shocks of Core-Collapse Supernova Remnants in the Large Magellanic Cloud
• Kinetic simulations of mildly relativistic shocks I: particle acceleration in high Mach number shocks
• Dust Destruction in Type Ia Supernova Remnants in the Large Magellanic Cloud
• Radio Spectral Index Variations and Physical conditions in Kepler's Supernova Remnant
• A High-Resolution X-Ray and Optical Study of SN 1006: Asymmetric Expansion and Small-Scale Structure in a Type Ia Supernova Remnant
• Expansion of the Youngest Galactic Supernova Remnant G1.9+0.3
• Azimuthal Density Variations Around the Rim of Tycho's Supernova Remnant
• Supernova Remnants in the Local Group I: A model for the radio luminosity function and visibility times of supernova remnants
• Clustering of LAT light curves: a clue to the origin of high-energy emission in Gamma-Ray Bursts
• Dust in a Type Ia Supernova Progenitor: Spitzer Spectroscopy of Kepler's Supernova Remnant
• Supernova Ejecta in the Youngest Galactic Supernova Remnant G1.9+0.3
• A Universal Luminosity Function for Radio Supernova Remnants
• Magnetic-Field Amplification in the Thin X-ray Rims of SN1006
• Second Epoch Hubble Space Telescope Observations of Kepler's Supernova Remnant: The Proper Motions of Balmer Filaments
• Radio Evolution of Supernova Remnants Including Non-linear Particle Acceleration: Insights from Hydrodynamic Simulations
• Forward Shock Proper Motions of Kepler's Supernova Remnant
• Dusty Blastwaves of Two Young LMC Supernova Remnants: Constraints on Postshock Compression
• The Deepest Radio Observations of Nearby Type IA Supernovae: Constraining Progenitor Types and Optimizing Future Surveys
• Systematic Study of Acceleration Efficiency in Young Supernova Remnants with Nonthermal X-ray Observations
• Energy Dependence of Synchrotron X-Ray Rims in Tycho's Supernova Remnant
• The properties of non-thermal X-ray filaments in young supernova remnants
• An Ejecta Kinematics Study of Kepler's Supernova Remnant with High-Resolution $Chandra$ HETG Spectroscopy