Diffuse X-ray Emissions from Dynamic Planetary Nebulae

TL;DR

This paper develops a theoretical model for diffuse X-ray emissions in planetary nebulae, linking X-ray luminosity and brightness profiles to wind interactions and comparing results with observations.

Contribution

It introduces a piecewise isothermal shock wind model incorporating self-gravity to predict X-ray emissions in planetary nebulae, aligning theoretical results with observed data.

Findings

X-ray brightness peaks at the reverse shock, not the contact discontinuity.

X-ray emission morphology can be a central luminous sphere or a bright ring.

Model matches observed X-ray luminosities and profiles of planetary nebulae.

Abstract

We present theoretical results of a piecewise isothermal shock wind model devised for predicting the luminosity and surface brightness profile of diffuse X-ray emissions primarily from the inner shocked downstream wind zone of a planetary nebula (PN) surrounded by self-similar shocked dense shell and outer slow AGB wind envelope involving self-gravity and compare/fit our computational model results with available observations of a few grossly spherical X-ray emitting PNe. Matching shocked piecewise isothermal self-similar void (ISSV) solutions with self-gravity of Lou & Zhai (LZ) for the outer zone and a stationary isothermal fast tenuous wind with a reverse shock for the inner zone across an expanding contact discontinuity, we can consistently construct dynamic evolution models of PNe with diffuse X-ray emissions. On the basis of such a chosen dynamic wind interaction model, both X-ray luminosity and radial X-ray brightness profile are determined by three key parameters, namely the so-called X-ray parameter $X$, two radii $R_{rs}$ and $R_c$ of the reverse shock and the contact discontinuity. We find that morphologies of X-ray emissions would appear in the forms of either a central luminous sphere or a bright ring embedded within optically bright shells. In contrast to previous adiabatic models, the X-ray brightness peaks around the reverse shock, instead of the contact discontinuity surface just inside the outer shocked dense shell. Diffuse X-ray emissions of a few observed PNe appear to support this wind-wind dynamic interaction scenario.