The first spectropolarimetric monitoring of the peculiar O4Ief supergiant zeta Puppis

TL;DR

This study conducted spectropolarimetric observations of the peculiar supergiant zeta Puppis to investigate the presence of magnetic fields, finding no significant magnetic detection but analyzing variability and potential correlations with stellar properties.

Contribution

First spectropolarimetric monitoring of zeta Puppis, providing insights into its magnetic field status and variability, and exploring potential links to stellar evolution and surface phenomena.

Findings

No significant magnetic field detected in zeta Puppis.

Spectral lines show high variability correlated with a 1.78-day period.

Probability analysis of magnetic field variation conducted.

Abstract

The origin of the magnetic field in massive O-type stars is still under debate. To model the physical processes responsible for the generation of O star magnetic fields, it is important to understand whether correlations between the presence of a magnetic field and stellar evolutionary state, rotation velocity, kinematical status, and surface composition can be identified. The O4Ief supergiant zeta Pup is a fast rotator and a runaway star, which may be a product of a past binary interaction, possibly having had an encounter with the cluster Trumper 10 some 2Myr ago. The currently available observational material suggests that certain observed phenomena in this star may be related to the presence of a magnetic field. We acquired spectropolarimetric observations of zeta Pup with FORS2 mounted on the 8-m Antu telescope of the VLT to investigate if a magnetic field is indeed present in this star. We show that many spectral lines are highly variable and probably vary with the recently detected period of 1.78d. No magnetic field is detected in zeta Pup, as no magnetic field measurement has a significance level higher than 2.4sigma. Still, we studied the probability of a single sinusoidal explaining the variation of the longitudinal magnetic field measurements.