Unveiling the power spectra of δ Scuti stars with TESS^⋆

The temperature, gravity, and frequency scaling relation

¹ Dpto. de Astrofísica, Centro de Astrobiología (CSIC-INTA), ESAC, Camino Bajo del Castillo s/n, 28692 Madrid, Spain
e-mail: sbarcelo@cab.inta-csic.es
² Electrical Engineering, Electronics, Automation and Applied Physics Department, E.T.S.I.D.I, Polytechnic University of Madrid (UPM), Madrid 28012, Spain
³ School of Physics and Astronomy, University of Birmingham, B15 2TT Birmingham, UK
⁴ Spanish Virtual Observatory, Spain
⁵ Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
⁶ Dept. Theoretical Physics and Cosmology, University of Granada (UGR), 18071 Granada, Spain

Received: 5 December 2019
Accepted: 14 April 2020

Abstract

Thanks to high-precision photometric data legacy from space telescopes like CoRoT and Kepler, the scientific community could detect and characterize the power spectra of hundreds of thousands of stars. Using the scaling relations, it is possible to estimate masses and radii for solar-type pulsators. However, these stars are not the only kind of stellar objects that follow these rules: δ Scuti stars seem to be characterized with seismic indexes such as the large separation (Δν). Thanks to long-duration high-cadence TESS light curves, we analysed more than two thousand of this kind of classical pulsators. In that way, we propose the frequency at maximum power (ν_max) as a proper seismic index since it is directly related with the intrinsic temperature, mass and radius of the star. This parameter seems not to be affected by rotation, inclination, extinction or resonances, with the exception of the evolution of the stellar parameters. Furthermore, we can constrain rotation and inclination using the departure of temperature produced by the gravity-darkening effect. This is especially feasible for fast rotators as most of δ Scuti stars seem to be.