Rapid Deceleration of Blast Waves Witnessed in Tycho's Supernova Remnant

TL;DR

This study reveals a rapid deceleration of shock waves in Tycho's supernova remnant, supporting the single-degenerate progenitor scenario and demonstrating a new method to analyze surrounding gas environments.

Contribution

It introduces a novel technique to analyze SNR environments and provides evidence favoring the single-degenerate progenitor scenario for Type Ia supernovae.

Findings

Shock waves decelerated rapidly in the last 15 years

Recent shock interaction with dense gas supports the single-degenerate scenario

New method to probe gas environments around supernova remnants

Abstract

In spite of their importance as standard candles in cosmology and as major major sites of nucleosynthesis in the Universe, what kinds of progenitor systems lead to type Ia supernovae (SN) remains a subject of considerable debate in the literature. This is true even for the case of Tycho's SN exploded in 1572 although it has been deeply studied both observationally and theoretically. Analyzing X-ray data of Tycho's supernova remnant (SNR) obtained with Chandra in 2003, 2007, 2009, and 2015, we discover that the expansion before 2007 was substantially faster than radio measurements reported in the past decades and then rapidly decelerated during the last ~ 15 years. The result is well explained if the shock waves recently hit a wall of dense gas surrounding the SNR. Such a gas structure is in fact expected in the so-called single-degenerate scenario, in which the progenitor is a binary system consisting of a white dwarf and a stellar companion, whereas it is not generally predicted by a competing scenario, the double-degenerate scenario, which has a binary of two white dwarfs as the progenitor. Our result thus favors the former scenario. This work also demonstrates a novel technique to probe gas environments surrounding SNRs and thus disentangle the two progenitor scenarios for Type Ia SNe.