Binarity and multiperiodicity in high-amplitude delta Scuti stars

TL;DR

This study investigates binarity and multiperiodicity in high-amplitude delta Scuti stars through photometric and spectroscopic surveys, revealing orbital motions, multiperiodic pulsations, and potential binary companions in several stars.

Contribution

First comprehensive survey combining binary star analysis with stellar oscillations in high-amplitude delta Scuti stars, including new radial velocity data and binary hypotheses.

Findings

Detected orbital motion in RS Gru with a low-mass companion.

Found multiperiodicity and amplitude variability in RY Lep.

Confirmed multiperiodic pulsations and binary hypotheses in multiple stars.

Abstract

We have carried out a photometric and spectroscopic survey of bright high-amplitude delta Scuti (HADS) stars. The aim was to detect binarity and multiperiodicity (or both) in order to explore the possibility of combining binary star astrophysics with stellar oscillations. Here we present the first results for ten, predominantly southern, HADS variables. We detected the orbital motion of RS Gru with a semi-amplitude of ~6.5 km/s and 11.5 days period. The companion is inferred to be a low-mass dwarf star in a close orbit around RS Gru. We found multiperiodicity in RY Lep both from photometric and radial velocity data and detected orbital motion in the radial velocities with hints of a possible period of 500--700 days. The data also revealed that the amplitude of the secondary frequency is variable on the time-scale of a few years, whereas the dominant mode is stable. Radial velocities of AD CMi revealed cycle-to-cycle variations which might be due to non-radial pulsations. We confirmed the multiperiodic nature of BQ Ind, while we obtained the first radial velocity curves of ZZ Mic and BE Lyn. The radial velocity curve and the O-C diagram of CY Aqr are consistent with the long-period binary hypothesis. We took new time series photometry on XX Cyg, DY Her and DY Peg, with which we updated their O-C diagrams.