Surface gravities for 15,000 Kepler stars measured from stellar granulation and validated with Gaia DR2 parallaxes

TL;DR

This paper introduces a new method to estimate stellar surface gravity from light curves by analyzing granulation background in the Fourier spectrum, validated with Gaia parallaxes, and applied to 15,000 Kepler stars.

Contribution

The authors developed and calibrated a Fourier-based method to measure stellar surface gravity from light curves, achieving high precision and validating it with Gaia data.

Findings

Achieved 0.05 dex precision in log g measurements.

Provided a catalog of log g for 15,000 stars.

Validated the method using Gaia DR2 parallaxes.

Abstract

We have developed a method to estimate surface gravity (log g) from light curves by measuring the granulation background, similar to the "flicker" method by Bastien et al. (2016) but working in the Fourier power spectrum. We calibrated the method using Kepler stars for which asteroseismology has been possible with short-cadence data, demonstrating a precision in log g of about 0.05 dex. We also derived a correction for white noise as a function of Kepler magnitude by measuring white noise directly from observations. We then applied the method to the same sample of long-cadence stars as Bastien et al. We found that about half the stars are too faint for the granulation background to be reliably detected above the white noise. We provide a catalogue of log g values for about 15,000 stars having uncertainties better than 0.5 dex. We used Gaia DR2 parallaxes to validate that granulation is a powerful method to measure log g from light curves. Our method can also be applied to the large number of light curves collected by K2 and TESS.