Rotational Variables: Kepler Versus ASAS-SN

TL;DR

This study compares low-amplitude Kepler rotational variables with high-amplitude ASAS-SN stars, revealing differences in rotation, binarity, and star spot activity, enhancing understanding of stellar magnetism and evolution.

Contribution

It provides a detailed analysis of ~50,000 Kepler rotational variables, highlighting differences from ASAS-SN populations in rotation, binarity, and star spot activity.

Findings

Kepler stars are mostly slowly rotating, single, main sequence stars.

Kepler rotators have lower binary fractions than ASAS-SN stars.

Kepler stars are less spotted, correlating with their lower amplitudes.

Abstract

Rotational variables are stars that vary in brightness due to star spots modulated by rotation. They are probes of stellar magnetism, binarity, and evolution. Phillips et al. (2023) explored distinct populations of ~50,000 high-amplitude rotational variables from the All-Sky Automated Survey for Supernovae (ASAS-SN), examining correlations between stellar rotation, binarity, and activity. Here, we carry out a similar analysis of ~50,000 much lower amplitude Kepler rotational variables. The Kepler population is dominated by slowly rotating, single, main sequence stars, with a striking absence of the rapidly rotating main sequence group in the ASAS-SN sample. The binary fractions of the Kepler rotators are significantly lower than for the ASAS-SN systems and they are significantly less spotted, as expected from their lower amplitudes. The scope of these statistical surveys will dramatically increase in the near future.