Investigating the origin of cyclical wind variability in hot, massive stars - I. On the dipolar magnetic field hypothesis

Abstract

OB stars exhibit various types of spectral variability associated with wind structures, including the apparently ubiquitous discrete absorption components (DACs). These are proposed to be caused by either magnetic fields or non-radial pulsations (NRPs). In this paper, we evaluate the possible relation between large-scale, dipolar magnetic fields and the DAC phenomenon by investigating the magnetic properties of a sample of 13 OB stars exhibiting well-documented DAC behaviour. Using high-precision spectropolarimetric data acquired in part in the context of the Magnetism in Massive Stars (MiMeS) project, we find no evidence for surface dipolar magnetic fields in any of these stars. Using Bayesian inference, we compute upper limits on the strengths of the fields and use these limits to assess two potential mechanisms by which the field may influence wind outflow: magnetic wind confinement and local photospheric brightness enhancements. Within the limits we derive, both mechanisms fail to provide a systematic process capable of producing DACs in all of the stars of our sample. Therefore, this implies that dipolar fields are highly unlikely to be responsible for these structures in all massive stars, meaning that some other mechanism must come into play.

arXiv comment17 pages, 6 figures, accepted for publication in MNRAS

References in corpus (21)

• Mass-loss predictions for O and B stars as a function of metallicity
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: I. Isothermal, Nonrotating, Radially Driven Flow
• Stable magnetic fields in stellar interiors
• Least squares deconvolution of the stellar intensity and polarization spectra
• Hydrodynamical Simulations of Corotating Interaction Regions and Discrete Absorption Components in Rotating O-Star Winds
• A Magnetic Confinement vs. Rotation Classification of Massive-Star Magnetospheres
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: III. Angular Momentum Loss and Rotational Spindown
• Fourier method in the determination of rotational velocities in OB stars
• Properties of Galactic early-type O-supergiants: A combined FUV-UV and optical analysis
• Magnetic spots on hot massive stars
• Quantitative studies of the optical and UV spectra of Galactic early B supergiants I. Fundamental parameters
• L-band spectroscopy of Galactic OB-stars
• Clumping in the inner winds of hot, massive stars from hydrodynamical line-driven instability simulations
• Confirmation of the magnetic oblique rotator model for the Of?p star HD 191612
• Investigating the spectroscopic, magnetic and circumstellar variability of the O9 subgiant star HD 57682
• On magnetic inhibition of photospheric macro-turbulence generated in the iron-bump opacity zone of O-stars
• Stokes $IQUV$ Magnetic Doppler Imaging of Ap stars II: Next Generation Magnetic Doppler Imaging of ${\alpha }^2$ CVn
• Stellar magnetic field parameters from a Bayesian analysis of high-resolution spectropolarimetric observations
• Exploring the origin of magnetic fields in massive stars: II. New magnetic field measurements in cluster and field stars
• Detectability of small-scale magnetic fields in early-type stars
• An Observational Evaluation of Magnetic Confinement in the Winds of BA Supergiants

Cited by in corpus (19)

• The MiMeS Survey of Magnetism in Massive Stars: Introduction and overview
• The MiMeS survey of magnetism in massive stars: Magnetic analysis of the O-type stars
• Variability of OB stars from TESS southern Sectors 1-13 and high-resolution IACOB and OWN spectroscopy
• Short-term variability and mass loss in Be stars I. BRITE satellite photometry of $\eta$ and $\mu$ Centauri
• BRITE-Constellation high-precision time-dependent photometry of the early-O-type supergiant $\zeta$ Puppis unveils the photospheric drivers of its small- and large-scale wind structures
• No breakdown of the radiatively-driven wind theory in low-metallicity environments
• Simultaneous X-ray and optical spectroscopy of the Oef supergiant lambda Cep
• Light variations due to the line-driven wind instability and wind blanketing in O stars
• Investigating the origin of cyclical wind variability in hot, massive stars - II. Hydrodynamical simulations of co-rotating interaction regions using realistic spot parameters for the O giant $\xi$ Persei
• Studying the photometric and spectroscopic variability of the magnetic hot supergiant $\zeta$ Orionis Aa
• An extensive spectroscopic time-series of three Wolf-Rayet stars. I. The lifetime of large-scale structures in the wind of WR 134
• A search for strong magnetic fields in massive and very massive stars in the Magellanic Clouds
• Multiple short-lived stellar prominences on O stars: The O6.5I(n)fp star lambda Cephei
• Coordinated UV and X-ray spectroscopic observations of the O-type giant xi Per: the connection between X-rays and large-scale wind structure
• Similar but different: the varied landscape of Onfp/Oef stars variability
• The first spectropolarimetric monitoring of the peculiar O4Ief supergiant zeta Puppis
• Ultraviolet Spectropolarimetry with Polstar: Clumping and Mass-loss Rate Corrections
• A magnetic field detection in the massive O-type bright giant 63 Oph
• Fe XVII $2p$-$3s$ line ratio diagnostic of shock formation radius in O stars