2002/01/01 by Una Hwang, A. Decourchelle, Anne Decourchelle +3 · 150 citations
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Atomic physics #Cassiopeia A #Ejecta #Electron #Electron temperature #Emission spectrum #Extrapolation #Gamma-ray bursts and supernovae #Geometry #Ion #Ionization #Line (geometry) #Nuclear physics #Physics #Shock (circulatory) #Shock wave #Spectral line #Supernova #Supernova remnant #Thermal #astro-ph
paper · pdf · doi:10.1086/344366
published in arXiv (Cornell University) 581(2), 1101-1115 (Cornell University) · ApJ, in press; 32 pages LaTeX, 9 postscript figures; replaced version to better match ApJ version
openalex publication_date 2002/01/01 · arxiv created 2002/10/10 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present Chandra CCD images of Tycho's supernova remnant that delineate its outer shock, seen 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 the forward shock at numerous locations. Most of the X-ray spectra that we examine along the rim show line emission from Si and S, which in some cases must come from ejecta; the continuum is well represented by either thermal or nonthermal models. In the case that the continuum is assumed to be thermal, the temperatures at the rim are all similar at about 2 keV, and the ionization ages are very low because of the overall weakness of the line emission. Assuming shock velocities inferred from radio and X-ray expansion measurements, these temperatures are substantially below those expected for equilibration of the electron and ion temperatures; electron to mean temperature ratios of approximately less than 0.1 - 0.2 indicate at most modest collisionless heating of the electrons at the shock. The nonthermal contribution to these spectra may be important, however, and may account for as many as half of the counts in the 4-6 keV energy range, based on an extrapolation of the hard X-ray spectrum above 10 keV.