Constraints on Cosmic-ray Acceleration Efficiency in Balmer Shocks of Two Young Type Ia Supernova Remnants in the Large Magellanic Cloud

Abstract

We present results from an optical study of two young Balmer-dominated remnants of SNIa in the Large Magellanic Cloud, 0509$-$67.5 and 0519$-$69.0, in an attempt to search for signatures of efficient cosmic-ray (CR) acceleration. We combine proper motion measurements from HST with corresponding optical spectroscopic measurements of the H$\alpha$ line at multiple rim positions from VLT/FORS2 and SALT/RSS and compare our results to published Balmer shock models. Analysis of the optical spectra result in broad H$\alpha$ widths in the range of 1800-4000 km s${}^{-1}$ for twelve separate Balmer-dominated filaments that show no evidence for forbidden line emission, the corresponding shock speeds from proper motion measurements span a range of 1700-8500 km s${}^{-1}$. Our measured values of shock speeds and broad H$\alpha$ widths in 0509$-$67.5 and 0519$-$69.0 are fit well with a Balmer shock model that does not include effects of efficient CR acceleration. We determine an upper limit of 7%/$\chi$ (95% confidence) on the CR acceleration efficiency for our ensemble of data points, where $\chi$ is the ionization fraction of the pre-shock gas. The upper limits on the individual remnants are 6%/$\chi$ (0509$-$67.5) and 11%/$\chi$ (0519$-$69.0). These upper limits are below the integrated CR acceleration efficiency in the Tycho supernova remnant, where the shocks predominantly show little H$\alpha$ emission, indicating that Balmer-dominated shocks are not efficient CR accelerators.

arXiv comment14 pages, 9 figures

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• A Hydro-Based MCMC Analysis of SNR 0509-67.5 Revealing the Explosion Properties from Fluid Discontinuities Alone
• Evidence for a Dense, Inhomogeneous Circumstellar Medium in the Type Ia SNR 0519-69.0
• X-ray Line Diagnostics of Ion Temperature at Cosmic-Ray Accelerating Collisionless Shocks
• Radiative transfer of hydrogen lines from supernova remnant shock waves: contributions of 2s-state hydrogen atoms
• Global Constraints on Diffusive Particle Acceleration by Strong Nonrelativistic Shocks
• Cosmic-ray production from neutron escape in microquasar jets
• Rapid Expansion of the Young Type Ia Supernova Remnant 0519-69.0: More Evidence for a Circumstellar Shell
• Search for $\gamma$-ray emission from SNRs in the Large Magellanic Cloud: a new cluster analysis at energies above 4 GeV
• Helium emission from Balmer-dominated shocks in Type Ia supernova remnants provides constraints to their progenitor systems
• Diagnosing Cosmic Ray Modified Shocks with H α Polarimetry