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Title:
Thermal and Nonthermal X-Ray Emission from the Forward Shock in Tycho's Supernova Remnant
Authors:
Hwang, Una; Decourchelle, Anne; Holt, Stephen S.; Petre, Robert
Affiliation:
AA(NASA Goddard Space Flight Center, Greenbelt, MD 20771.; Department of Astronomy, University of Maryland, College Park, MD 20742.), AB(Service d'Astrophysique, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France.), AC(F. W. Olin College of Engineering, Needham, MA 02492.), AD(NASA Goddard Space Flight Center, Greenbelt, MD 20771.)
Publication:
The Astrophysical Journal, Volume 581, Issue 2, pp. 1101-1115. (ApJ Homepage)
Publication Date:
12/2002
Origin:
UCP
ApJ Keywords:
ISM: individual (Tycho's supernova remnant), Shock Waves, ISM: Supernova Remnants, X-Rays: General, X-Rays: ISM
DOI:
10.1086/344366
Bibliographic Code:
2002ApJ...581.1101H

Abstract

We present Chandra X-ray images of Tycho's supernova remnant that delineate its outer shock as a thin, smooth rim along the straight northeastern edge and most of the circular western half. The images also show that the Si and S ejecta are highly clumpy and have reached near the forward shock at numerous locations. Most of the X-ray spectra that we examine along the rim show evidence of line emission from Si and S ejecta, while the continuum is well represented by either a thermal or a nonthermal model. If the continuum is assumed to be thermal, the electron temperatures at the rim are all similar at about 2 keV, while the ionization ages are very low because of the overall weakness of the line emission. These electron temperatures are substantially below those expected for equilibration of the electron and ion temperatures, assuming shock velocities inferred from radio and X-ray expansion measurements; the electron-to-mean temperature ratios are <~0.1-0.2, indicating that collisionless heating of the electrons at the shock is modest. The nonthermal contribution to these spectra might be important, but cannot be strongly constrained by these data. It could account for as much as half of the flux in the 4-6 keV energy range, based on an extrapolation of the hard X-ray spectrum above 10 keV.
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