X-ray emitting structures in the Vela SNR: ejecta anisotropies and progenitor stellar wind residuals

TL;DR

This study investigates the X-ray structures in the Vela supernova remnant, revealing ejecta anisotropies, possible jet-like features, and signatures of progenitor stellar wind interactions, with implications for the remnant's origin.

Contribution

The paper provides a detailed spatial and spectral analysis of Vela SNR structures, identifying a potential jet-like ejecta feature and wind residuals, suggesting a Wolf-Rayet progenitor.

Findings

Identification of elongated and filamentary structures with distinct physical properties.

Discovery of a large-scale wind residual feature with a peculiar Ne/O ratio.

Evidence supporting a Wolf-Rayet star as the progenitor of Vela SNR.

Abstract

The Vela supernova remnant (SNR) shows several ejecta fragments protruding beyond the forward shock (shrapnel). Recent studies have revealed high Si abundance in two shrapnel (A and G), located in opposite directions with respect to the SNR center. This suggests the possible existence of a Si-rich jet-counterjet structure. We analyzed an XMM-Newton observation of a bright clump, behind shrapnel G, which lies along the direction connecting A and G. The aim is to study the physical and chemical properties of this clump to ascertain whether it is part of this putative jet-like structure. We produced background-corrected and adaptively-smoothed count-rate images and median photon energy maps, and performed a spatially resolved spectral analysis. We identified two structures with different physical properties. The first one is remarkably elongated along the direction connecting A and G. Its X-ray spectrum is much softer than that of the other two shrapnel, to the point of hindering the determination of the Si abundance, however its physical and chemical properties are consistent with those of shrapnel A and G. The second structure, running along the southeast-northwest direction, has a higher temperature and appears like a thin filament. By analyzing the ROSAT data, we have found that this filament is part of a very large and coherent structure that we identified in the western rim of the shell. We obtained a thorough description of the tail of Shrapnel G. In addition we discovered a coherent and very extended feature that we interpret as a signature of an earlier interaction of the remnant with the stellar wind of its progenitor star. The peculiar Ne/O ratio we found in the wind residual may be suggestive of a Wolf-Rayet progenitor for Vela SNR, though further analysis is required to address this point.