Orbital parameters, chemical composition, and magnetic field of the Ap binary HD 98088

TL;DR

This study investigates the binary system HD 98088, revealing the primary Ap star's magnetic field and chemical peculiarities, and contrasting it with the Am secondary, to understand stellar magnetism and chemical anomalies in binary systems.

Contribution

First detailed spectropolarimetric analysis of HD 98088, including magnetic field measurement and chemical abundance analysis of both components.

Findings

Primary has a strong, dipolar magnetic field varying with orbital phase.

Primary shows typical Ap star chemical peculiarities.

Secondary exhibits Am star chemical characteristics with no detected magnetic field.

Abstract

HD 98088 is a synchronised, double-lined spectroscopic binary system with a magnetic Ap primary component and an Am secondary component. We study this rare system using high-resolution MuSiCoS spectropolarimetric data, to gain insight into the effect of binarity on the origin of stellar magnetism and the formation of chemical peculiarities in A-type stars. Using a new collection of 29 high-resolution Stokes VQU spectra we re-derive the orbital and stellar physical parameters and conduct the first disentangling of spectroscopic observations of the system to conduct spectral analysis of the individual stellar components. From this analysis we determine the projected rotational velocities of the stars and conduct a detailed chemical abundance analysis of each component using both the SYNTH3 and ZEEMAN spectrum synthesis codes. The surface abundances of the primary component are typical of a cool Ap star, while those of the secondary component are typical of an Am star. We present the first magnetic analysis of both components using modern data. Using Least-Squares Deconvolution, we extract the longitudinal magnetic field strength of the primary component, which is observed to vary between +1170 and -920 G with a period consistent with the orbital period. There is no field detected in the secondary component. The magnetic field in the primary is predominantly dipolar, with the positive pole oriented approximately towards the secondary.