Related papers: Large-scale wind structures in OB supergiants: a s…
We investigate the line-profile variability (lpv) of H-alpha for a large sample of O-type supergiants. We used the Temporal Variance Spectrum (TVS) analysis, developed by Fullerton et al 1996 and modified by us to take into account the…
Probing the structures of stellar winds is of prime importance for the understanding of massive stars. Based on their optical spectral morphology and variability, the stars of the Oef class have been suggested to feature large-scale…
The transition from early Of stars to WN type objects is poorly understood. O-type supergiants with emission lines (OIf+) are considered to be intermediate between these two classes. The scope of this paper is to investigate the spectral…
Spectroscopic and photometric variability is widespread among O-type supergiants. It is linked to various phenomena affecting the star and its circumstellar environment, thereby providing direct information concerning them. To investigate…
Massive stars show a variety of spectral variability: presence of discrete absorption components in UV P-Cygni profiles, optical line profile variability, X-ray variability, radial velocity modulations. Our goal is to study the spectral…
The common - arguably ubiquitous - large-scale variability of optical and UV lines profiles of hot, massive stars is widely interpreted as the direct consequence of structured, variable winds. Many of the variability phenomena are observed…
It is observationally as well as theoretically well established that the winds of hot, massive OB-stars are highly structured on a broad range of spatial scales. This paper first discusses consequences of the small-scale structures…
Context. The first magnetic fields in O- and B-type stars that do not belong to the Bp-star class, have been discovered. The cyclic UV wind-line variability, which has been observed in a significant fraction of early-type stars, is likely…
We report on low resolution (R~3000) spectropolarimetry of the A0 supergiant star HD 92207. This star is well-known for significant spectral variability. The source was observed on seven different nights spanning approximately 3 months in…
Massive stars continuously enrich the surrounding interstellar medium by supplying it with stellar material driven by their powerful winds. B supergiant stars (BSGs) in particular are a type of massive star characterized by strong winds and…
Despite the important advances in space asteroseismology during the last decade, the early phases of evolution of stars with masses above $\sim$15 M$_{\odot}$ have been only vaguely explored up to now. Our goal is to detect, analyze and…
(Abridged) We provide empirical constraints on the different physical components that can act to yield temporal variability in predominantly or partially wind-formed optical lines of luminous OB stars, and thus potentially affect the…
We have studied a sample of 28 periodically variable B-type supergiants selected from the HIPPARCOS mission and 12 comparison stars covering the whole B-type spectral range. Our goal is to test if their variability is compatible with…
We provide a quantitative analysis of time-variable phenomena in the photospheric, near-star, and outflow regions of the late-B supergiant (SG) HD 199478. The analysis is based primarily on optical spectroscopic datasets secured between…
Photospheric lines of B-type supergiants show variability in their profile shapes. In addition, their widths are much wider than can be accounted for purely by stellar rotation. This excess broadening is often referred to as…
We use ~12,000 spectra of ~3,500 magnetically active M0-M9 dwarfs from the Sloan Digital Sky Survey taken at 10-15 minute intervals, together with ~300 spectra of ~60 M0-M8 stars obtained hourly with the Hydra multi-object spectrometer, to…
Many O and B stars show unexplained cyclical variability in their winds, i.e. modulation of absorption features on the rotational timescale, but not strictly periodic over longer timescales. For these stars no dipolar magnetic fields have…
A small fraction of hot OBA stars host global magnetic fields with field strengths of the order of 0.1-10 kG. This leads to the creation of persistent surface structures (spots) in stars with sufficiently weak winds as a result of the…
Despite of the importance of magnetic fields for the full understanding of the properties of accreting Herbig Ae/Be stars, these fields have scarcely been studied over the rotation cycle until now. One reason for the paucity of such…
Magnetic wind confinement has been proposed as one explanation for the complex wind structures of supergiant stars of spectral types B and A. Observational investigation of this hypothesis was undertaken using high-resolution…