paper

The Expansion of the X-ray Remnant of Tycho's Supernova (SN1572)

arXiv:astro-ph/0010122 · doi:10.1086/317337

Abstract

Two ROSAT high resolution images separated by nearly five years have been used to determine the expansion of the X-ray remnant of Tycho's supernova (SN1572). The current expansion rate averaged over the entire remnant is % per yr, which, when combined with the known age of the remnant, determines the mean expansion parameter , defined as , to be . There are significant radial and azimuthal variations of the X-ray expansion rate. The radial expansion in particular shows highly significant evidence for the more rapid expansion of the forward blast wave as compared to the reverse-shocked ejecta, an effect that has not been seen previously. The expansion parameter varies from at the outermost edge of Tycho's supernova remnant (SNR) to a value of on the inside edge of the bright rim of emission. These values are consistent with the rates expected for a remnant with constant density ejecta evolving into a uniform interstellar medium during the ejecta-dominated phase of evolution. Based on the size, age, and X-ray expansion rates, I obtain values for the explosion energy and ambient density of and . As is also the case for Cas A and Kepler's SNR, the X-ray expansion rate of Tycho's SNR appears to be significantly higher than the radio expansion rate. In the case of Tycho's SNR, however, the difference between radio and X-ray expansion rates is clearly associated with the motion of the forward shock.

4 pages, including 2 postscript figs, LaTeX, emulateapj. Accepted by ApJ Letters

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