AAVSO: American Association of Variable Star Observers

Search for Variability in 30 Bright Metallic-line A Stars Observed by the TESS Spacecraft (Abstract)

Volume 49 number 1 (2021)

Joyce A. Guzik
Los Alamos National Laboratory, MS T082, Los Alamos, NM 87547; joy@lanl.gov

Abstract

(Abstract only) As part of the NASA TESS Guest Investigator Cycle 2 program, we received 2-minute cadence light curves for bright main-sequence metallic-line A (Am) stars. The Am stars show significant underabundances of calcium and scandium, and enhanced abundances of titanium and iron-group elements compared to the solar abundances. Catanzaro et al. (2019) used high resolution spectroscopy + Gaia parallaxes to derive a set of uniformly reduced parameters for these stars, including log g, v sin i, effective temperature, luminosity, and element abundances. While these stars lie in or near the delta Scuti pulsation instability region in the H-R diagram, they are not expected to pulsate because the diffusive element settling and radiative levitation processes responsible for their peculiar abundances should have also drained helium from the layer in the envelope that drives delta Scuti pulsations. Of the 30 stars observed by TESS, we find four delta Sct stars, two of which may be δ Sct/γ Dor hybrids. Of the remaining stars, we find one previously known eclipsing binary, and 16 showing variability of unconfirmed origin. We will show example light curve analyses for a delta Scuti star, for one of the higher amplitude variables, and for the eclipsing binary. Follow-up observations combined with stellar modeling will be needed to understand the causes for the variability.