Asteroseismic versus Gaia distances: a first comparison

TL;DR

This study compares asteroseismic and Gaia parallaxes for Kepler stars, finding good agreement for dwarfs/subgiants but discrepancies for red giants, highlighting the need for more precise future Gaia data.

Contribution

First comparison of asteroseismic and Gaia parallaxes for Kepler stars, revealing agreement for dwarfs/subgiants and discrepancies for red giants.

Findings

Good agreement between asteroseismic and Gaia parallaxes for dwarfs/subgiants.

Significant discrepancies for red giants with current Gaia data.

Future Gaia releases expected to resolve current discrepancies.

Abstract

Context. The Kepler space mission led to a large amount of high-precision time series of solar-like oscillators. Using a Bayesian analysis that combines asteroseismic techniques and additional ground-based observations, the mass, radius, luminosity, and distance of those stars can be estimated with good precision. This has given a new impetus to the research field of galactic archeology. Aims. The first data release of the Gaia space mission contains the TGAS catalog with parallax estimates for more than 2 million stars, including many of the Kepler targets. Our goal is to make a first proper comparison of asteroseismic and astrometric parallaxes of a selection of dwarfs, subgiants, and red giants observed by Kepler for which asteroseismic distances were published. Methods. We compare asteroseismic and astrometric distances of solar-like pulsators using an appropriate statistical errors-in- variables model on a linear as well as on a logarithmic scale. Results. For a sample of 22 dwarf and subgiant solar-like oscillators, the TGAS parallaxes considerably improved the Hipparcos ones, yet the excellent agreement between asteroseismic and astrometric distances still holds. For a sample of 938 Kepler pulsating red giants, the TGAS parallaxes are much more uncertain than the asteroseismic ones, making it worthwhile to validate the former with the latter. From errors-in-variables modelling we find a significant discrepancy between the TGAS parallaxes and the asteroseismic ones. Conclusions. For the sample of dwarfs and subgiants, the comparison between astrometric and asteroseismic parallaxes does not require a revision of the stellar models on the basis of TGAS. For the sample of red giants, we identify possible causes of the discrepancy, which we will likely be able to resolve with the more precise Gaia parallaxes of the upcoming releases.