First detection of a magnetic field in the fast rotating runaway Oe star zeta Ophiuchi

TL;DR

This paper reports the first detection of a magnetic field in the rapidly rotating runaway Oe star zeta Ophiuchi, using spectropolarimetric observations, confirming its magnetic nature and exploring its X-ray emission origins.

Contribution

The study provides the first direct evidence of a magnetic field in zeta Ophiuchi, a well-studied massive star, using spectropolarimetry, and analyzes its X-ray properties to understand magnetic influence.

Findings

Detected a mean longitudinal magnetic field of 141+-45G in zeta Ophiuchi.

Confirmed the magnetic nature of zeta Ophiuchi for the first time.

Reviewed X-ray data to assess magnetic versus wind instability contributions.

Abstract

The star zeta Ophiuchi is one of the brightest massive stars in the northern hemisphere and was intensively studied in various wavelength domains. The currently available observational material suggests that certain observed phenomena are related to the presence of a magnetic field. We acquired spectropolarimetric observations of zeta Oph with FORS1 mounted on the 8-m Kueyen telescope of the VLT to investigate if a magnetic field is indeed present in this star. Using all available absorption lines, we detect a mean longitudinal magnetic field B_z_all = 141+-45G, confirming the magnetic nature of this star. We review the X-ray properties of zeta Oph with the aim to understand whether the X-ray emission of zeta Oph is dominated by magnetic or by wind instability processes.