The Origin of the Iron-Rich Knot in Tycho's Supernova Remnant

TL;DR

This study investigates an iron-rich knot in Tycho's supernova remnant using X-ray data, revealing unusual chemical composition that challenges traditional supernova explosion models and suggests alternative nucleosynthesis processes.

Contribution

It provides detailed spectroscopic analysis of the Fe knot, constraining its origin and ruling out the Chandrasekhar-mass white dwarf core as its source.

Findings

The Fe knot shows no emission from Cr, Mn, or Ni.

Mass ratios suggest a peak temperature of (5.3-5.7) x 10^9 K.

Deep, dense core of a Chandrasekhar-mass white dwarf is ruled out.

Abstract

X-ray observations of supernova remnants (SNRs) allow us to investigate the chemical inhomogeneity of ejecta, offering unique insight into the nucleosynthesis in supernova explosions. Here we present detailed imaging and spectroscopic studies of the "Fe knot" located along the eastern rim of the Type Ia SNR Tycho (SN 1572) using Suzaku and Chandra long-exposure data. Surprisingly, the Suzaku spectrum of this knot shows no emission from Cr, Mn, or Ni, which is unusual for the Fe-rich regions in this SNR. Within the framework of the canonical delayed-detonation models for SN Ia, the observed mass ratios M_Cr/M_Fe < 0.023, M_Mn/M_Fe < 0.012, and M_Ni/M_Fe < 0.029 (at 90% confidence) can only be achieved for a peak temperature of (5.3-5.7) x 10^9 K and a neutron excess of < 2.0 x 10^-3. These constraints rule out the deep, dense core of a Chandrasekhar-mass white dwarf as the origin of the Fe knot, and favors either incomplete Si burning or the alpha-rich freeze-out regime, probably close to their boundary. An explosive He burning regime is a possible alternative, although this hypothesis is in conflict with the main properties of this SNR.