HR 710 (HD 15144): An ultra-Sr-rich, magnetic Ap star with a close companion

TL;DR

This paper studies the magnetic, chemically peculiar star HR 710, revealing its ultra-strong Sr lines, a close companion likely a white dwarf, and discusses spectral anomalies and abundance stratification with limited data.

Contribution

It provides new insights into HR 710's spectral features, companion characteristics, and challenges traditional stellar atmosphere models for chemically peculiar stars.

Findings

HR 710 has an ultra-strong Sr II spectrum.

The system likely includes a white dwarf companion emitting X-rays.

Spectral anomalies suggest abundance patches and stratification.

Abstract

The magnetic, chemically peculiar A-star HR 710 (HD 15144, ADS 1849A, AB Cet) has a close companion in a nearly circular orbit. Its 3-day period is unusually short for such stars. The system emits moderately hard x-rays, which likely come from a white dwarf secondary (ADS 1849Ab). The Sr II spectrum is very strong, and the resonance lines show similar core-nib structure to the stronger Ca K line. We place only loose constraints on a model. There are indications of a lower electron/gas pressure than expected from the star's parallax and brightness. Strong-line profiles and anomalous excitation/ionization indicate significant deviations from traditional models, fixed by Teff, log{g}, and abundances. Weak spectral-line profiles and wavelength shifts probably indicate abundance patches rather than the presence of a secondary (ADS 1849Ab) spectrum. Our UVES spectra are from only one epoch. Additional low-noise, high-resolution spectra are needed. We discuss the spectrum within the context of abundance stratification.