Pulsating hot subdwarfs with MS companions or: EO Ceti is an sdO pulsator!

TL;DR

This paper discusses the binary nature of hot subdwarf pulsators, reveals spectroscopic challenges in parameter determination, and reclassifies EO Ceti as an sdOV star, highlighting the importance of binary interactions.

Contribution

It provides spectroscopic evidence that reclassifies EO Ceti as an sdOV star and analyzes the impact of main sequence companions on pulsation detection.

Findings

EO Ceti is an sdOV star, not an sdB pulsator.

Main sequence companions complicate parameter estimation.

Binary fraction among hot subdwarf pulsators is influenced by observational biases.

Abstract

About half of the hot subdwarfs are found to have spectra of composite types, indicating a main sequence companion of spectral type F-K, and the pulsators are no exception to this rule. The spectroscopic contamination from the main sequence stars makes it hard to reliably establish physical parameters for the hot component, and also makes pulsations harder to detect as the amplitudes are depressed. The binary fraction of the observed sample of hot subdwarf pulsators is discussed, as are the biases that are affecting it. Spectroscopic evidence is presented that clearly demonstrates that the well known sdB pulsator, EOCeti, is misclassified, and is actually an sdOV star.