Carbon, Helium and Proton Kinetic Temperatures in a Cygnus Loop Shock Wave

Abstract

Observations of SN1006 have shown that ions and electrons in the plasma behind fast supernova remnant shock waves are far from equilibrium, with the electron temperature much lower than the proton temperature and ion temperatures approximately proportional to ion mass. In the ~360 km/s shock waves of the Cygnus Loop, on the other hand, electron and ion temperatures are roughly equal, and there is evidence that the oxygen kinetic temperature is not far from the proton temperature. In this paper we report observations of the He II lambda 1640 line and the C IV lambda 1550 doublet in a 360 km/s shock in the Cygnus Loop. While the best fit kinetic temperatures are somewhat higher than the proton temperature, the temperatures of He and C are consistent with the proton temperature and the upper limits are 0.5 and 0.3 times the mass-proportional temperatures, implying efficient thermal equilibration in this collisionless shock. The equilibration of helium and hydrogen affects the conversion between proton temperatures determined from H alpha line profiles and shock speeds, and that the efficient equilibration found here reduces the shock speed estimates and the distance estimate to the Cygnus Loop of Medina et al. (2014) to about 800 pc.

arXiv comment22 pages, 4 figures ApJ, in press

References in corpus (20)

• A Physical Relationship Between Electron-Proton Temperature Equilibration and Mach Number in Fast Collisionless Shocks
• Balmer-Dominated Spectra of Nonradiative Shocks in the Cygnus Loop, RCW 86 and Tycho Supernova Remnants
• Polycyclic aromatic hydrocarbon processing in a hot gas
• Electron Heating and Cosmic Rays at a Supernova Shock from Chandra X-ray Observations of E0102.2-7219
• The Optical Spectrum of the SN 1006 Supernova Remnant Revisited
• Electron-Ion Temperature Equilibration in Collisionless Shocks: the Supernova Remnant-Solar Wind Connection
• Spatial Structure and Collisionless Electron Heating in Balmer-dominated Shocks
• Shock fronts, electron-ion equilibration and ICM transport processes in the merging cluster Abell 2146
• The Heating of Thermal Electrons in Fast Collisionless Shocks: The Integral Role of Cosmic Rays
• The Solar Corona as probed by Comet Lovejoy (C/2011 W3)
• Far Ultraviolet Spectra of a Non-Radiative Shock Wave in the Cygnus Loop
• Shock Speed, Cosmic Ray Pressure, and Gas Temperature in the Cygnus Loop
• The Detection of Far Ultraviolet Line Emission from Balmer-Dominated Supernova Remnants in the Large Magellanic Cloud
• The northwestern ejecta knot in SN 1006
• Non-Maxwellian Proton Velocity Distributions in Nonradiative Shocks
• Cosmic Origins Spectrograph Observations of the Chemical Composition of LMC N132D
• Chandra Observations of the Northeastern Rim of the Cygnus Loop
• Heating of Heavy Ions by Interplanetary Coronal Mass Ejection (ICME) Driven Collisionless Shocks
• Grain Destruction in a Supernova Remnant Shock Wave
• Electron Heating, Magnetic Field Amplification, and Cosmic Ray Precursor Length at Supernova Remnant Shocks

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