Asteroseismic radii of dwarfs: New accuracy constraints from Gaia DR2 parallaxes

TL;DR

This study tests the accuracy of asteroseismic stellar radii against Gaia DR2 parallaxes, finding that frequency fitting is accurate within 1%, while scaling relations require corrections to achieve 2-3% accuracy for dwarfs.

Contribution

It provides new constraints on the accuracy of asteroseismic radii using Gaia parallaxes, highlighting the importance of applying model-based corrections to scaling relations.

Findings

Frequency fitting radii are about 1% smaller than Gaia radii.

Scaling relations overestimate radii by more than 5% at high temperatures.

Applying model-based corrections reduces the scaling relation offset to 2-3%.

Abstract

Precise stellar masses and radii can be determined using asteroseismology, but their accuracy must be tested against independent estimates. Using radii derived from Gaia DR2 parallaxes, we test the accuracy of asteroseismic radii for a sample of 93 dwarfs based on both individual frequency fitting and the seismic scaling relations. Radii from frequency fitting are about 1 per cent smaller than Gaia radii on average; however, this difference may be explained by a negative bias of 30 $\mu$as in the Gaia parallaxes. This indicates that the radii derived from frequency fitting are accurate to within 1 per cent. The scaling relations are found to overestimate radii by more than 5 per cent, compared to the Gaia radii, at the highest temperatures. We demonstrate that this offset is reduced to 3 per cent after applying corrections based on model frequencies to the scaling relation for $\Delta\nu$, but only when the model frequencies are corrected for the surface effect. With corrections to $\Delta\nu$, the scaling relation gives radii accurate to about 2--3 per cent for dwarfs in the temperature range $5400$--$6700$ K. The remaining offset at the highest temperatures may indicate the need for a correction to the scaling relation for $\nu_{\mathrm{max}}$.