Improved hydrodynamic pulsation models for the pulsating extreme helium star V652 Herculis

TL;DR

This paper presents advanced hydrodynamic models for the pulsating extreme helium star V652 Herculis, incorporating higher resolution and updated opacities to better understand its pulsation properties and shock phenomena.

Contribution

The study introduces refined non-linear hydrodynamic models with improved resolution and updated opacities, enhancing the understanding of pulsation mechanisms in V652 Herculis.

Findings

Confirmation of shock development at minimum radius during large amplitude pulsations

Correlation between pulsation period and stellar parameters used to constrain models

Discussion of observational measurements in the context of new models

Abstract

New non-linear hydrodynamic models have been constructed to simulate the radial pulsations observed in the extreme helium star V652 Her. These use a finer zoning to allow higher radial resolution than in previous simulations. Models incorporate updated OPAL and OP opacity tables and adopt a composition based on the best atmospheric analyses to date. Key pulsation properties including period, velocity amplitude and shock acceleration are examined as a function of the mean stellar parameters (mass, luminosity, and effective temperature). The new models confirm that, for large amplitude pulsations, a strong shock develops at minimum radius, and is associated with a large phase delay between maximum brightness and minimum radius. Using the observed pulsation period to constrain parameter space in one dimension, other pulsation properties are used to constrain the model space further, and to critically discuss observational measurements. Similar models may be useful for the interpretation of other blue large amplitude pulsators, which may also exhibit pulsation-driven shocks.