Changes in R Leonis over Two Centuries: Period evolution and dust shell development

TL;DR

This study analyzes two centuries of observational data on R Leonis, revealing a decreasing pulsation period, long-term modulations, and evolving dust shell characteristics, providing insights into the star's variability and circumstellar environment.

Contribution

It presents a detailed long-term analysis of R Leonis's period changes, extrema behavior, and dust shell evolution, based on historical light curve data.

Findings

Pulsation period shortened by about 3 days over two centuries

Detected modulations with periods of approximately 35 and 98 years

Gradual changes in extrema depths indicate dust environment evolution

Abstract

The AAVSO-based historical light curve of the oxygen-rich Mira variable R Leonis is used to determine and analyse the properties of the star's maxima and minima. The pulsation period is found to have shortened by about 3 days over the past two centuries. Superimposed on the mean period are clear modulations on timescales of approximately 35 and 98 years. The depths of extrema show non-random behaviour: minima in particular display strong similarity in depth over extended intervals, with a mean depth difference of 0.26 magnitude for adjacent minima compared to a 0.38 magnitude difference for random pairs. Depth coherence persists for up to about 43 years. Examination of extrema depths over the full observational history of the star reveals gradual long-term changes, consistent with evolution of the circumstellar dust environment.