X‐Ray Emission‐Line Imaging and Spectroscopy of Tycho's Supernova Remnant

We present X-ray images of Tycho's supernova remnant in emission linefeatures of Mg, Si, S, Ar, Ca, and Fe, plus the continuum, using data obtainedby the imaging spectrometers onboard the ASCA X-ray satellite. All the imagesshow the shell-like morphology characteristic of previously obtained broad-bandX-ray images, but are clearly distinct from each other. We use imagereconstruction techniques to achieve a spatial resolution of ~0.8'. Lineintensity ratios are used to make inferences about the remnant's physicalstate, on average for the entire remnant, and with angular position around therim. The average temperature (T) of the Si and S ejecta in the remnant is(0.8-1.1) X 10^7 K and the average ionization age (nt) is (0.8-1.3) X 10^11cm^-3 s. For a constant nt, the observed relative brightness variations of Siand S line image profiles with azimuthalangle imply differences of roughly afactor of 1.3-1.8 in the temperature. We compare the radial brightness profilesof our images to simple geometrical models, and find that a spherical emittinggeometry is favored over a torus. A spherical geometry is further supported bythe absence of systematic Doppler shifts across the remnant. The radial fitresults also suggest that some radial mixing of the ejecta has occurred.However, the azimuthally averaged Fe K image peaks at a markedly lower radiusthan the other images. The average Fe K / Fe L line intensity ratio and theposition of the Fe K energy centroid support a T several times higher and an ntapprox. a factor of ten lower than for the other elements, and imply that theFe ejecta must have retained some of its stratification. Although many of thefeatures in the 4-6 keV X-ray continuum correspond to those in the radio, thereis no obvious correlation between the relative brightness in these bands.Comment: 17 pages plus 9 figures, LaTeX type, uses aas2pp4.sty. To appear in the Astrophysical Journa