Asteroseismology and Gaia: Testing Scaling Relations Using 2200 Kepler Stars with TGAS Parallaxes

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

Asteroseismology and Gaia: Testing Scaling Relations Using 2200 Kepler Stars with TGAS Parallaxes,
The Astrophysical Journal, Vol. 844, Issue 1

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_eff 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_⊙ .

We find no significant offset for main-sequence (≲ 1.5 R_⊙ ) and low-luminosity RGB stars (≈3-8 R_⊙ ), but seismic radii appear to be systematically underestimated by ≈5% for subgiants (≈1.5-3 R_⊙ ). 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 (Δν ) 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.