Asteroseismology and Gaia: Testing Scaling Relations Using 2200 Kepler Stars with TGAS Parallaxes
Chaplin, William J.; Davies, Guy R.; Latham, David W.; Pinsonneault, Marc; Huber, Daniel; García, Rafael A.; Bedding, Timothy R.; Sharma, Sanjib; Stello, Dennis; Silva Aguirre, Victor; Buchhave, Lars A.; Mathur, Savita; Serenelli, Aldo; Tayar, Jamie; Mosser, Benoit; Stassun, Keivan; Zinn, Joel; Bojsen-Hansen, Mathias; Sahlholdt, Christian; Bastien, Fabienne
United States, Australia, Denmark, Spain, United Kingdom, France
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 ({{Δ }}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.