Does the Period of a Pulsating Star Depend on its Amplitude?

TL;DR

This study investigates whether the pulsation period of stars correlates with amplitude changes, using wavelet analysis on observational data of various pulsating stars, finding a tendency for positive correlation in some cases.

Contribution

It provides the first systematic analysis of amplitude-period relationships in pulsating red giants, supergiants, and yellow supergiants using wavelet analysis.

Findings

Approximately 75-80% of stars with significant amplitude variation show positive correlation.

Data limitations and complex behaviors make definitive conclusions difficult for many stars.

Some stars exhibit complex or indeterminate relationships between amplitude and period.

Abstract

Several classes of pulsating stars are now known to undergo slow changes in amplitude; these include pulsating red giants and supergiants, and yellow supergiants. We have used visual observations from the AAVSO International Database, and wavelet analysis of 39 red giants, 7 red supergiants, and 3 yellow supergiants, to test the hypothesis that an increase in amplitude would result in an increase in period, because of non-linear effects in the pulsation. For most of the stars, the results are complex and/or indeterminate, due to the limitations of the data, the small amplitude or amplitude variation, or other processes such as random cycle-to-cycle period fluctuations. For the dozen stars which have substantial amplitude variation, and reasonably simple behavior, there is a 75-80% tendency to show a positive correlation between amplitude and period.