Difference of photometric properties between regular and non-regular Miras in the Magellanic Clouds

TL;DR

This study distinguishes regular and non-regular Miras in the Magellanic Clouds using machine learning, revealing differences in their photometric properties, the role of dust, and implications for distance measurements.

Contribution

It applies a random forest classification to Mira light curves and analyzes their photometric and dust properties, highlighting differences and their impact on the period-luminosity relation.

Findings

Regular Miras follow a tighter period-luminosity relation at maximum light.

Non-regular Miras show significant dust presence and long-term variability.

Period-luminosity relation is more precise for regular oxygen-rich Miras.

Abstract

Mira variables are asymptotic giant branch pulsating stars with long pulsation periods and large amplitudes in optical bands. By applying the random forest algorithm to the I-band light curves for the Miras in the Magellanic Clouds, we have classified these Miras into regular Miras and non-regular Miras. Wherein non-regular Miras exhibit a long-term variation in addition to their primary pulsation periods. Our results confirm that the period-luminosity relation for maximum light has a smaller dispersion, but only occurs on the regular oxygen-rich (O-rich) Miras, which we recommend to be applied in future distance scale work. We have also collected multi-band photometry for these Miras to perform a spectral-energy-distribution (SED) fitting with stellar and dust components, showing that a significant fraction of dust is present around the non-regular Miras. According to our results, we believe that the periodic long-term variations seen in the non-regular Miras might be due to the presence of dust.