# Using red clump stars to correct the Gaia DR1 parallaxes

## TL;DR

This paper uses red clump stars with asteroseismic data to identify and correct systematic errors in Gaia DR1 parallaxes, especially for stars with parallaxes less than about 1.6 mas.

## Contribution

It introduces a new correction method for Gaia DR1 parallaxes based on red clump stars, improving distance estimates in the Kepler field.

## Key findings

- Gaia DR1 parallaxes have a systematic error decreasing with distance.
- The proposed correction aligns Gaia distances with asteroseismic and eclipsing binary measurements.
- Discrepancies remain for the open cluster M67 red clump stars.

## Abstract

Recent results have suggested that there is tension between the Gaia DR1 TGAS distances and the distances obtained using luminosities determined by eclipsing binaries or asteroseismology on red giant stars. We use the $K_s$-band luminosities of red clump stars, identified and characterized by asteroseismology, to make independent distance estimates. Our results suggest that Gaia TGAS distances contain a systematic error that decreases with increasing distance. We propose a correction to mitigate this offset as a function of parallax that is valid for the Kepler field and values of parallax that are less than ${\sim} 1.6 \rm \, mas$. For parallaxes greater than this we find agreement with previously published values. We note that the TGAS distances to the red clump stars of the open cluster M67 show a high level of disagreement that is difficult to correct for.