X-Ray Measured Dynamics of Tycho's Supernova Remnant

TL;DR

This study measures the X-ray proper motions of Tycho's supernova remnant's shock fronts and ejecta, revealing azimuthal variations and providing insights into the remnant's expansion dynamics and ambient density.

Contribution

First detailed X-ray proper-motion measurements of Tycho's supernova remnant's shock and ejecta, linking expansion behavior to supernova models and ambient density estimates.

Findings

Proper motion varies azimuthally from 0.14 to 0.40 arcsec/year.

Average expansion index is approximately 0.5.

Ambient density around the remnant is estimated to be less than 0.2 cm^{-3}.

Abstract

We present X-ray proper-motion measurements of the forward shock and reverse-shocked ejecta in Tycho's supernova remnant, based on three sets of archival Chandra data taken in 2000, 2003, and 2007. We find that the proper motion of the edge of the remnant (i.e., the forward shock and protruding ejecta knots) varies from 0".20 yr^{-1} (expansion index m=0.33, where R = t^m) to 0".40 yr^{-1} (m=0.65) with azimuthal angle in 2000-2007 measurements, and 0".14 yr^{-1} (m=0.26) to 0".40 yr^{-1} (m=0.65) in 2003-2007 measurements. The azimuthal variation of the proper motion and the average expansion index of ~0.5 are consistent with those derived from radio observations. We also find proper motion and expansion index of the reverse-shocked ejecta to be 0".21-0".31 yr^{-1} and 0.43-0.64, respectively. From a comparison of the measured m-value with Type Ia supernova evolutionary models, we find a pre-shock ambient density around the remnant of <~0.2 cm^{-3}.