Reverse-Shock in Tycho's Supernova Remnant

TL;DR

This paper presents the first continuous radial profiles of ionization age and ionization time in Tycho's supernova remnant, revealing detailed insights into the reverse shock's propagation through the ejecta.

Contribution

It introduces a novel method of analyzing the S to Si line flux ratio to trace the reverse shock's progression in Tycho's SNR.

Findings

Radial increase in S to Si line flux ratio observed.

Continuous profiles of ionization age and elapsed ionization time derived.

Insights into the reverse shock propagation history obtained.

Abstract

Thermal X-ray emission from young supernova remnants (SNRs) is usually dominated by the emission lines of the supernova (SN) ejecta, which are widely believed being crossed and thus heated by the inwards propagating reverse shock (RS). Previous works using imaging X-ray data have shown that the ejecta are heated by the RS by locating the peak emission region of the most recently ionized matter, which is found well separated towards the inside from the outermost boundary. Here we report the discovery of a systematic increase of the Sulfur (S) to Silicon (Si) K$\alpha$ line flux ratio with radius in Tycho's SNR. This allows us, for the first time, to present continuous radial profiles of the ionization age and, furthermore, the elapsed ionization time since the onset of the ionization, which tells the propagation history of the ionization front into the SNR ejecta.