Far Ultraviolet Spectra of a Non-Radiative Shock Wave in the Cygnus Loop

Abstract

Spatial and spectral profiles of O VI emission behind a shock wave on the northern edge of the Cygnus Loop were obtained with the FUSE satellite. The velocity width of the narrowest O VI profile places a tight constraint on the electron-ion and ion-ion thermal equilibration in this 350 $\mathrm{km}{\mathrm{s}}^{-1}$ collisionless shock. Unlike faster shocks in SN1006 and in the heliosphere, this shock brings oxygen ions and protons to within a factor of 2.5 of the same temperature. Comparison with other shocks suggests that shock speed, rather than Alfvén Mach number, may control the degree of thermal equilibration. We combine the O VI observations with a low resolution far UV spectrum from HUT, an H$\alpha$ image and ROSAT PSPC X-ray data to constrain the pre-shock density and the structure along the line-of-sight. As part of this effort, we model the effects of resonance scattering of O VI photons within the shocked gas and compute time-dependent ionization models of the X-ray emissivity. Resonance scattering affects the O VI intensities at the factor of 2 level, and the soft spectrum of the X-ray rim can be mostly attributed to departures from ionization equilibrium. The pre-shock density is about twice the canonical value for the Cygnus Loop X-ray emitting shocks.

arXiv commentTo appear in Astrophysical Journal, Vol. 584, Feb. 20 2003

References in corpus (13)

• The 'Forbidden' Abundance of Oxygen in the Sun
• Overview of the Far Ultraviolet Spectroscopic Explorer Mission
• On-Orbit Performance of the Far Ultraviolet Spectroscopic Explorer (FUSE) Satellite
• Balmer-Dominated Spectra of Nonradiative Shocks in the Cygnus Loop, RCW 86 and Tycho Supernova Remnants
• Panoramic Views of the Cygnus Loop
• The Distance to the Cygnus Loop from Hubble Space Telescope Imaging of the Primary Shock Front
• An Isolated, Recently Shocked ISM Cloud in the Cygnus Loop SNR
• The Radial Structure of the Cygnus Loop Supernova Remnant --- Possible evidence of a cavity explosion ---
• Resonant Scattering of Emission Lines in Coronal Loops: Effects on Image Morphology and Line Ratios
• HST-STIS Observations of the Cygnus Loop: Spatial Structure of a Non-radiative Shock
• A Comparison of Ultraviolet, Optical, and X-Ray Imagery of Selected Fields in the Cygnus Loop
• FUSE Observations of the Cygnus Loop: OVI Emission from a Nonradiative Shock
• The warm interstellar medium around the Cygnus Loop

Cited by in corpus (25)

• RCW 86: A Type Ia Supernova in a Wind-Blown Bubble
• Balmer-Dominated Shocks: A Concise Review
• Possible Charge-Exchange X-Ray Emission in the Cygnus Loop Detected with Suzaku
• Electron-Ion Temperature Equilibration at Collisionless Shocks in Supernova Remnants
• The Cygnus Loop's Distance, Properties, and Environment Driven Morphology
• A Chandra Study of the Lobe/ISM Interactions Around the Inner Radio Lobes of Centaurus A: Constraints on the Temperature Structure and Transport Processes
• Shock Speed, Cosmic Ray Pressure, and Gas Temperature in the Cygnus Loop
• Electron-Ion Temperature Ratio in Astrophysical Shocks
• The Detection of Far Ultraviolet Line Emission from Balmer-Dominated Supernova Remnants in the Large Magellanic Cloud
• The Temperature Structure of the Warm-Hot Intergalactic Medium
• Non-Maxwellian Proton Velocity Distributions in Nonradiative Shocks
• Far UV and Optical Emissions from Three Very Large Supernova Remnants Located at Unusually High Galactic Latitudes
• Chandra Observations of the Northeastern Rim of the Cygnus Loop
• Far Ultraviolet Spectroscopic Explorer Survey of Magellanic Cloud Supernova Remnants
• Grain Destruction in a Supernova Remnant Shock Wave
• Carbon, Helium and Proton Kinetic Temperatures in a Cygnus Loop Shock Wave
• Turbulence and Particle Acceleration in Radiative Shock Waves in the Cygnus Loop II: Development of Postshock Turbulence
• Modeling magnetohydrodynamics and non equilibrium SoHO/UVCS line emission of CME shocks
• Dust destruction in non-radiative shocks
• Multiple accelerated particle populations in the Cygnus Loop with Fermi-LAT
• Global Far-Ultraviolet Properties of the Cygnus Loop
• Environmental Impact on the Southeast Limb of the Cygnus Loop
• The Abundance Inhomogeneity in the Northern Rim of the Cygnus Loop
• Hydrogen Non-Equilibrium Ionisation Effects in Coronal Mass Ejections
• [Ne V] Imaging of N49 in the Large Magellanic Cloud