• Bojsen-Hansen, Mathias
• Zinn, Joel
• Sahlholdt, Christian
• Bedding, Timothy R.
• Pinsonneault, Marc
• Bastien, Fabienne
• Chaplin, William J.
• Buchhave, Lars A.
• García, Rafael A.
• Davies, Guy R.
• Mathur, Savita
• Latham, David W.
• Sharma, Sanjib
• Mosser, Benoit
• Huber, Daniel
• Tayar, Jamie
• Serenelli, Aldo
• Silva Aguirre, Victor
• Stassun, Keivan
• Stello, Dennis

Abstract

We present a comparison of parallaxes and radii from asteroseismology and Gaia DR1 (TGAS) for 2200 Kepler stars spanning from the main sequence to the red-giant branch. We show that previously identified offsets between TGAS parallaxes and distances derived from asteroseismology and eclipsing binaries have likely been overestimated for parallaxes ≲ 5{--}10 mas (≈90%-98% of the TGAS sample). The observed differences in our sample can furthermore be partially compensated by adopting a hotter {T}<SUB>{eff</SUB>} scale (such as the infrared flux method) instead of spectroscopic temperatures for dwarfs and subgiants. Residual systematic differences are at the ≈2% level in parallax across three orders of magnitude. We use TGAS parallaxes to empirically demonstrate that asteroseismic radii are accurate to ≈5% or better for stars between ≈ 0.8{--}8 {R}<SUB>☉ </SUB>. We find no significant offset for main-sequence (≲ 1.5 {R}<SUB>☉ </SUB>) and low-luminosity RGB stars (≈3-8 {R}<SUB>☉ </SUB>), but seismic radii appear to be systematically underestimated by ≈5% for subgiants (≈1.5-3 {R}<SUB>☉ </SUB>). We find no systematic errors as a function of metallicity between [{Fe}/{{H}}]≈ -0.8 to +0.4 dex, and show tentative evidence that corrections to the scaling relation for the large frequency separation ({{∆ }}ν ) improve the agreement with TGAS for RGB stars. Finally, we demonstrate that beyond ≈ 3 {kpc} asteroseismology will provide more precise distances than end-of-mission Gaia data, highlighting the synergy and complementary nature of Gaia and asteroseismology for studying galactic stellar populations.

Topics

• thermogravimetry