SHOCK SPEED, COSMIC RAY PRESSURE, AND GAS TEMPERATURE IN THE CYGNUS LOOP

Journal Article · Tue Sep 01 04:00:00 EDT 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/702/1/327; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21333855

Salvesen, Greg; Raymond, John C

Upper limits on the shock speeds in supernova remnants can be combined with post-shock temperatures to obtain upper limits on the ratio of cosmic ray to gas pressure (P {sub CR}/P{sub G} ) behind the shocks. We constrain shock speeds from proper motions and distance estimates, and we derive temperatures from X-ray spectra. The shock waves are observed as faint H{alpha} filaments stretching around the Cygnus Loop supernova remnant in two epochs of the Palomar Observatory Sky Survey (POSS) separated by 39.1 years. We measured proper motions of 18 nonradiative filaments and derived shock velocity limits based on a limit to the Cygnus Loop distance of 576 {+-} 61 pc given by Blair et al. for a background star. The Position Sensitive Proportional Counter (PSPC) instrument on-board ROSAT observed the X-ray emission of the post-shock gas along the perimeter of the Cygnus Loop, and we measure post-shock electron temperature from spectral fits. Proper motions range from 2.''7 to 5.''4 over the POSS epochs and post-shock temperatures range from kT {approx} 100-200 eV. Our analysis suggests a cosmic ray to post-shock gas pressure consistent with zero, and in some positions P {sub CR} is formally smaller than zero. We conclude that the distance to the Cygnus Loop is close to the upper limit given by the distance to the background star and that either the electron temperatures are lower than those measured from ROSAT PSPC X-ray spectral fits or an additional heat input for the electrons, possibly due to thermal conduction, is required.

• OSTI ID: 21333855
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 702; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COSMIC RADIATION
ELECTRON TEMPERATURE
ELECTRONS
PROPER MOTION
PROPORTIONAL COUNTERS
SHOCK WAVES
STARS
SUPERNOVA REMNANTS
THERMAL CONDUCTION
X-RAY SPECTRA