Progenitor Constraint Incorporating Shell Merger: The Case of Supernova Remnant G359.0-0.9

TL;DR

This study uses X-ray spectral analysis and molecular line observations to constrain the progenitor mass of supernova remnant G359.0-0.9, highlighting the role of shell merger effects in interpreting elemental abundance patterns.

Contribution

It introduces a method combining spectral analysis and molecular observations to infer progenitor masses, accounting for shell merger effects in supernova remnants.

Findings

G359.0-0.9 is Mg-rich with high Mg-to-Ne ratio.

Progenitor mass likely less than 15 solar masses.

Shell merger effects are crucial for interpreting abundance patterns.

Abstract

It is generally hard to put robust constraints on progenitor masses of supernovae (SNe) and remnants (SNRs) observationally, while they offer tantalizing clues to understanding explosion mechanisms and mass distribution. Our recent study suggests that ``shell merger'', which is theoretically expected for stellar evolution, can appreciably affect final yields of inter-mediate mass elements (IMEs; such as Ne, Mg, and Si). In light of this, here we report results of X-ray spectral analysis of a Galactic SNR G359.0-0.9, whose abundance pattern may possibly be anomalous according to a previous study. Our spectroscopy using all the available data taken with XMM-Newton reveals that this remnant is classified as Mg-rich SNRs because of its high Mg-to-Ne ratio (Z_Mg/Z_Ne=1.90+0.27-0.19; mass ratio 0.66+0.09-0.07) and conclude that the result cannot be explained without the shell merger. By comparing the observation with theoretical calculations, we prefer the so-called Ne-burning shell intrusion and in this case the progenitor mass M_ZAMS is likely <15M_sun. We confirm the result also by our new molecular line observations with the NRO-45 m telescope: G359.0-0.9 is located in the Scutum-Centaurus arm (2.66--2.94 kpc) and in this case the resultant total ejecta mass ~6.8M_sun is indeed consistent with the above estimate. Our method using mass ratios of IMEs presented in this paper will become useful to distinguish the type of the shell merger, the Ne-burning shell intrusion and the O-burning shell merger, for future SNR studies.