How semiregular are irregular variables?

TL;DR

This study analyzes light curves of semiregular and irregular variable stars, finding no significant difference in their periodic signals, suggesting they are part of a continuous spectrum rather than distinct classes.

Contribution

It provides evidence that irregular variables are an extension of semiregular variables, challenging traditional classifications based on light curve characteristics.

Findings

No significant difference in S/N of periodic signals between classes

Lb stars may be an extension of SRVs towards shorter periods

Light curve analysis shows continuous spectrum of variability

Abstract

We investigate the question whether there is a real difference in the light change between stars classified as semiregular (SRV) or irregular (Lb) variables by analysing photometric light curves of 12 representatives of each class. Using Fourier analysis we try to find a periodic signal in each light curve and determine the S/N of this signal. For all stars, independent of their variability class we detect a period above the significance threshold. No difference in the measured S/N between the two classes could be found. We propose that the Lb stars can be seen as an extension of the SRVs towards shorter periods and smaller amplitudes. This is in agreement with findings from other quantities which also showed no marked difference between the two classes.