Precise surface gravities of $δ$ Scuti stars from asteroseismology

Abstract

The work reported here demonstrates that it is possible to accurately determine surface gravities of $δ$ Sct stars using the frequency content from high precision photometry and a measurement of the parallax. Using a sample of 10 eclipsing binary systems with a $δ$ Sct component and the unique $δ$ Sct star discovered with a transiting planet, WASP-33, we were able to refine the $Δν-\barρ$ relation. Using this relation and parallaxes, we obtained independent values for the masses and radii, allowing us to calculate the surface gravities without any constraints from spectroscopic or binary analysis. A remarkably good agreement was found between our results and those published, extracted from the analysis of the radial velocities and light curves of the systems. This reinforces the potential of $Δν$ as a valuable observable for $δ$ Sct stars and settles the degeneracy problem for the $\log g$ determination through spectroscopy.

5 pages, 2 figures, 1 table