Evolution of the central stars of young planetary nebulae

TL;DR

This study examines the evolution of central stars in young planetary nebulae by analyzing spectral emission line fluxes over time, revealing different evolutionary behaviors between H-rich and late-type Wolf-Rayet central stars.

Contribution

It provides observational evidence of nebular flux evolution over decades and compares these with theoretical models, highlighting differences in evolution between H-rich and late-[WR] stars.

Findings

Increase in [OIII] 5007 A flux in young H-rich nebulae

No flux change observed in nebulae with late-[WR] stars

H-rich star evolution aligns with existing models

Abstract

The evolution of central stars of planetary nebulae was so far documented in just a few cases. However, spectra collected a few decades ago may provide a good reference for studying the evolution of central stars using the emission line fluxes of their nebulae. We investigated evolutionary changes of the [OIII] 5007 A line flux in the spectra of planetary nebulae. We compared nebular fluxes collected during a decade or longer. We used literature data and newly obtained spectra. A grid of Cloudy models was computed using existing evolutionary models, and the models were compared with the observations. An increase of the [OIII] 5007 A line flux is frequently observed in young planetary nebulae hosting H-rich central stars. The increasing nebular excitation is the response to the increasing temperature and hardening radiation of the central stars. We did not observe any changes in the nebular fluxes in the planetary nebulae hosting late-type Wolf-Rayet (WR) central stars. This may indicate a slower temperature evolution (which may stem from a different evolutionary status) of late-[WR] stars. In young planetary nebulae with H-rich central stars, the evolution can be followed using optical spectra collected during a decade or longer. The observed evolution of H-rich central stars is consistent with the predictions of the evolutionary models provided in the literature. Late-[WR] stars possibly follow a different evolutionary path.