Revisiting Bright δ Scuti Stars and their Period-Luminosity Relation with TESS and Gaia EDR3

The TESS mission delivers high-precision space photometry for almost the full sky, enabling us to measure more precisely and homogenously the dominant modes of pulsating stars. We have used TESS light curves to study catalogued δ Sct stars and measure their dominant oscillation modes. We aim to use our revised data to place these targets more accurately in the period-luminosity diagram.

We look at δ Sct stars from the catalogues of Rodriguez et al. (2000) and Chang et al. (2013), which compile the observational properties of known δ Sct variables from the literature. Both catalogues are compiled from heterogeneous, ground-based measurements, where some targets have been observed for only one or two nights.

We find that lower-amplitude stars have greater error in their published dominant modes, likely due to poor SNR from ground-based observations. Discrepancies in dominant modes may also be due to amplitude modulation. Our P–L diagram shows a strong fundamental-mode ridge, and we find an excess of stars lying on a second ridge, with dominant oscillation periods half that of the predicted fundamental mode. We further demonstrate the value of the P–L diagram in distinguishing δ Sct stars from other pulsators.