Revisiting bright delta Scuti stars and their period-luminosity relation with TESS and Gaia DR3

Abstract

We have used NASA's TESS mission to study catalogued 𝛿 Scuti stars. We examined TESS light curves for 434 stars, including many for which few previous observations exist. We found that 62 are not 𝛿 Scuti pulsators, with most instead showing variability from binarity. For the 372 𝛿 Scuti stars, we provide a catalogue of the period and amplitude of the dominant pulsation mode. Using Gaia DR3 parallaxes, we place the stars in the period-luminosity diagram and confirm previous findings that most stars lie on a ridge that corresponds to pulsation in the fundamental radial mode, and that many others fall on a second ridge that is a factor two shorter in period. This second ridge is seen more clearly than before, thanks to the revised periods and distances. We demonstrate the value of the period-luminosity diagram in distinguishing 𝛿 Scuti stars from short-period RR Lyrae stars, and we find several new examples of high-frequency 𝛿 Scuti stars with regular sequences of overtone modes, including XX Pyx and 29 Cyg. Finally, we revisit the sample of 𝛿 Scuti stars observed by Kepler and show that they follow a tight period-density relation, with a pulsation constant for the fundamental mode of 𝑄 = 0.0315 d.