Search for pulsation among suspected A-type binaries and the new multiperiodic Delta Scuti star HD217860

TL;DR

This study systematically investigates suspected A-type binary stars using spectroscopy and photometry, identifying pulsators including a multiperiodic Delta Scuti star with complex frequency behavior and amplitude modulation.

Contribution

It is the first comprehensive spectroscopic and photometric survey of suspected A-type binaries focusing on pulsation detection and characterization, revealing new multiperiodic Delta Scuti stars.

Findings

Identified three Delta Scuti pulsators among suspected binaries.

HD 217860 exhibits up to eight common frequencies in photometric and spectroscopic data.

Detected amplitude and frequency modulations in HD 217860.

Abstract

We have explored a sample of suspected A-type binaries in a systematic way, both spectroscopically and photometrically. Due to their location in the H-R diagram, indications of pulsation and/or chemical peculiarities among these suspected binary (or multiple) systems may be found. High-resolution spectroscopy obtained with the ELODIE and MUSICOS spectrographs was used in combination with a few nights of differential CCD photometry in order to search for pulsation(s). Of the 32 investigated targets, eight are spectroscopic binaries, one of which is a close binary also showing eclipses, and three have been identified as Delta Scuti pulsators with rapid line-profile variations. Among the latter stars, HD 217860 reveals interesting multiperiodic photometric and spectroscopic variations, with up to eight frequencies common to two large photometric data sets. We suggest that at least one radial overtone mode is excited among the two most dominant frequencies. We furthermore found evidence for a strong modulation of the amplitude(s) and/or the (radial) frequency content of this intriguing Delta Scuti star.