# Characterizing the magnetic field and spectral variability of the rigidly rotating magnetosphere star HD345439

## TL;DR

This study investigates the magnetic field and spectral variability of the rapidly rotating magnetosphere star HD345439, revealing a strong, variable magnetic field and surface abundance spot differences through spectropolarimetric monitoring.

## Contribution

It provides the first detailed spectropolarimetric analysis of HD345439, demonstrating a strong dipolar magnetic field and spectral line variability associated with surface abundance spots.

## Key findings

- Detection of a strong, rapidly varying magnetic field in HD345439.
- Opposite behavior of He and Si spectral lines linked to surface abundance spots.
- Confirmation of a dipolar magnetic field structure.

## Abstract

A team involved in APOGEE, one of the Sloan Digital Sky Survey III programs, recently announced the discovery of two rare rigidly rotating magnetosphere stars, HD345439 and HD23478. Near-infrared spectra of these objects revealed emission-line behavior identical to that previously discovered in the helium-strong star sigma Ori E, which has a strong magnetic field and rotates fast. A single spectropolarimetric observation of HD345439 with FORS2 at the VLT in 2014 over 88min indicated that HD345439 may host a strong, rapidly varying magnetic field. In this work, we present the results of our spectropolarimetric monitoring of this star with FORS2, which revealed the presence of a strong longitudinal magnetic field dominated by a dipolar component. The analysis of spectral variability indicates an opposite behaviour of He and Si lines, which is usually attributed to differences in the distribution of surface He and Si abundance spots.