CARBON, HELIUM, AND PROTON KINETIC TEMPERATURES IN A CYGNUS LOOP SHOCK WAVE

Journal Article · Mon Jun 01 04:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/805/2/152· OSTI ID:22521844

Raymond, John C.; Edgar, Richard J. ^[1]; Ghavamian, Parviz ^[2]

---

1. Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States)
2. Department of Physics, Astronomy and Geosciences, Towson University, Towson, MD 21252 (United States)

Observations of SN 1006 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{sup −1}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 λ1640 line and the C iv λ1550 doublet in a 360 km s{sup −1}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 Hα line profiles and shock speeds, and the efficient equilibration found here reduces the shock speed estimates and the distance estimate to the Cygnus Loop of Medina et al. to about 800 pc.

• OSTI ID: 22521844
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 805; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CARBON
CONVERSION
COSMIC ELECTRONS
COSMIC PROTONS
ELECTRON TEMPERATURE
EQUILIBRIUM
HELIUM
HYDROGEN
ION TEMPERATURE
MASS
OXYGEN
PLASMA
PROTON TEMPERATURE
SHOCK WAVES
SUPERNOVA REMNANTS
SUPERNOVAE
ULTRAVIOLET RADIATION
VELOCITY