Nonthermal Bremsstrahlung vs. Synchrotron Radiation: Cas A

TL;DR

This study analyzes X-ray data from supernova remnant Cas A to compare nonthermal bremsstrahlung and synchrotron radiation, revealing their relative contributions, electron spectrum steepness, and energy distribution among electrons.

Contribution

It provides the first detailed spectral comparison of nonthermal bremsstrahlung and synchrotron radiation in Cas A using extensive Chandra and RXTE data.

Findings

Nonthermal bremsstrahlung accounts for 2-4 times the synchrotron flux in 10-32 keV.

Electron spectrum is steeper at X-ray energies than at GeV energies.

Approximately 5% of electrons are nonthermal, holding 30% of the electron energy.

Abstract

We performed a spectral analysis of some Chandra ACIS and RXTE PCA data for the supernova remnant Cas A. A very large (1.1 Ms) ACIS data set is used to identify regions dominated by synchrotron radiation. The best-fit spectral models for these regions are combined to obtain a composite synchrotron model for the entire remnant. The difference between this model and the observed PCA flux is fitted with a nonthermal bremsstrahlung model. The results of this analysis suggest that (1) the ratio of the nonthermal bremsstrahlung to synchrotron radiation varies from about 2:1 to 4:1 in the 10-32 keV energy band, (2) the electron spectrum is significantly steeper at 10-32 keV than it is at 1 GeV, (3) about 5% of the electrons are nonthermal and (4) about 30% of the energy in the electron distribution is in nonthermal electrons.