On the shape of the ascending branch of the light curves of Long Period Variables

TL;DR

This paper introduces new parameters to describe the shape of the ascending branches of light curves in Long Period Variables, revealing correlations with stellar evolution indicators and aiding understanding of their physical mechanisms.

Contribution

It proposes a novel parameterization of light curve shapes that correlates with key stellar evolution parameters, enhancing the analysis of Long Period Variables on the AGB.

Findings

Strong correlation between the new shape parameter and stellar evolution indicators

The parameter q effectively tracks the star's evolution along the AGB

Clarifies the relation between light curve features and stellar physical processes

Abstract

The present article is written in the wake of a recently published study of the relation between the light curves of Long Period Variables and their evolution along the Asymptotic Giant Branch (AGB). It introduces a pair of new parameters that describe the shape of the ascending branches of such light curves. This parameterization reveals strong correlations with other parameters describing the evolution of the star on the AGB: periods, regularity and amplitudes of the oscillations, effective temperatures, mass loss rates, carbon and oxygen isotopic ratios, colour indices. It sheds new light on the occasional presence of humps on the ascending branches and on the distinction between stars that have not experienced strong Third Dredge Up (TDU) events and those that have as well as between oxygen-rich and carbon-rich stars. One of the new parameters, referred to as q, is particularly efficient at tracking the evolution of the star along the AGB. Globally, a simple picture can be drawn in the plane spanned by the period and by q. Yet, many details remain unexplained when looking at this picture in finer details. Overall, the results presented in the article help significantly with clarifying the complex set of observations that have been made in this domain and should inspire new considerations on their relation with the underlying physical mechanisms at stake inside the stars.