# On the discrepancy between asteroseismic and Gaia DR1 TGAS parallaxes

## TL;DR

This paper investigates the discrepancies between Gaia DR1 TGAS and asteroseismic parallaxes for giants, attributing differences to selection effects and extinction estimation errors, and proposes improved extinction estimates for better consistency.

## Contribution

It identifies causes of parallax discrepancies and demonstrates that accurate extinction estimates reconcile asteroseismic and Gaia parallaxes.

## Key findings

- Selection effects influence parallaxes for $ ext{varpi}<1.5$ mas.
- Extinction underestimation affects parallaxes for $ ext{varpi}>1.5$ mas.
- Reliable extinction estimates improve agreement with stellar isochrones.

## Abstract

Recently, a deviation of the Gaia TGAS parallaxes from the asteroseismic ones for giants was found. We show that for parallaxes $\varpi<1.5$ mas it can be explained by a selection effect in favour of bright and luminous giants in the Tycho-2 and TGAS catalogues. Another explanation of this deviation seems to be valid for $\varpi>1.5$ mas based on the best extinction estimates: the deviation may be caused not by a bias of parallax, but by an underestimation of the extinction (and, consequently, an overestimation of the calculated absolute magnitude) in the asteroseismic results. We demonstrate that the reliable estimates of the reddening and extinction (about 0.22 mag of the visual extinction for the Kepler field) better fit both the giants and main sequence stars to the PARSEC, MIST and YaPSI isochrones.