Formation and Evolution of [Wolf-Rayet] Planetary Nebulae through a Late Thermal Pulse

TL;DR

This paper presents the first radiation-hydrodynamical simulations of born-again planetary nebulae triggered by late thermal pulses, revealing how H-deficient ejecta interact with H-rich nebulae and support the born-again scenario.

Contribution

It introduces coupled 2D radiation-hydrodynamic and stellar evolution simulations with updated physics, demonstrating the formation of transient double-shell structures and their impact on nebular properties.

Findings

H-deficient LTP ejecta form a transient double-shell structure.

Ejecta mass is too small to alter nebular abundances significantly.

LTP material injection drives turbulence and enhances nebular mixing.

Abstract

We present the first radiation-hydrodynamical simulations of the formation of a born-again planetary nebula (PN) triggered by a late thermal pulse (LTP). The 2D radiation-hydrodynamic simulations, performed with the {\sc pluto} code, have been consistently coupled to stellar evolution calculations using the Modules for Experiments in Stellar Astrophysics ({\sc mesa}) code. Very particularly the stellar evolution model uses (i) updated opacity tables for H-deficient, C-rich mixtures during the LTP, and (ii) a mass-loss prescription tailored for H-deficient [Wolf-Rayet]([WR])-type winds during the post-LTP phase. Our stellar model reproduces the nearly complete depletion of H expected after an LTP event, while matching the observed abundances and spectral types of iconic [WR]-type central stars of PNe. The simulations show for the first time that the H-deficient LTP ejecta forms a transient double-shell structure which, after $\sim$1000 yr, becomes fully mixed with the H-rich PN. The ejecta mass ($\sim3.4\times10^{-4}$~M$_\odot$) is too small to leave a lasting imprint on the nebular abundances, predicting H-rich PNe around [WR] central stars. The injection of LTP material into the hot bubble drives turbulence, clump formation, and enhanced mixing, providing an explanation to the larger expansion velocities and larger turbulent nebular structures of PNe with [WR] central stars compared to those with H-rich central stars. These results provide robust support for the born-again scenario as the origin of H-deficient [WR] central stars within H-rich PNe.