Amplitudes of solar-like oscillations: constraints from red giants in open clusters observed by Kepler

TL;DR

This study uses Kepler data to analyze solar-like oscillations in red giants within open clusters, revealing that traditional scaling relations are insufficient and proposing a new empirical relation that also uncovers unresolved binaries.

Contribution

The paper introduces a new empirical amplitude scaling relation for solar-like oscillations that accounts separately for luminosity and mass, improving upon previous models.

Findings

Existing scaling relations do not fit the data well.

A new empirical relation effectively describes the oscillation amplitudes.

Potential unresolved binaries identified in cluster red clump stars.

Abstract

Scaling relations that link asteroseismic quantities to global stellar properties are important for gaining understanding of the intricate physics that underpins stellar pulsation. The common notion that all stars in an open cluster have essentially the same distance, age, and initial composition, implies that the stellar parameters can be measured to much higher precision than what is usually achievable for single stars. This makes clusters ideal for exploring the relation between the mode amplitude of solar-like oscillations and the global stellar properties. We have analyzed data obtained with NASA's Kepler space telescope to study solar-like oscillations in 100 red giant stars located in either of the three open clusters, NGC 6791, NGC 6819, and NGC 6811. By fitting the measured amplitudes to predictions from simple scaling relations that depend on luminosity, mass, and effective temperature, we find that the data cannot be described by any power of the luminosity-to-mass ratio as previously assumed. As a result we provide a new improved empirical relation which treats luminosity and mass separately. This relation turns out to also work remarkably well for main-sequence and subgiant stars. In addition, the measured amplitudes reveal the potential presence of a number of previously unknown unresolved binaries in the red clump in NGC 6791 and NGC 6819, pointing to an interesting new application for asteroseismology as a probe into the formation history of open clusters.