Related papers: Unveiling stellar spin: Determining inclination an…
Intensity interferometry permits very long optical baselines and the observation of sub-milliarcsecond structures. Using planned kilometric arrays of air Cherenkov telescopes at short wavelengths, intensity interferometry may increase the…
The combination of photometry, spectroscopy and spectropolarimetry of the chemically peculiar stars often aims to study the complex physical phenomena such as stellar pulsation, chemical inhomogeneity, magnetic field and their interplay…
Fast rotation seems to be the mayor factor to trigger the Be phenomenon. Surface fast rotation can be favored by initial formation conditions, such as abundance of metals. We have observed 118 Be stars up to the apparent magnitudes V=9 mag.…
The late evolutionary stages of stellar evolution are a key ingredient for our understanding in many fields of astrophysics, including stellar evolution and the enrichment of the interstellar medium (ISM) via stellar yields. Already the…
Light curves of 57 classical Be stars in TESS sectors 1 - 15 are examined. In most Be stars, the periodogram shows groups at a fundamental and one or more harmonics, which we attribute to rotation. In about 40 percent of the stars, the…
Giant stars, and especially C-rich giants, contribute significantly to the chemical enrichment of galaxies. The determination of precise parameters for these stars is a necessary prerequisite for a proper implementation of this evolutionary…
The origin of the disks around Be stars is still not known. Further progress requires a proper parametrization of their structure, both spatially and kinematically. This is challenging as the disks are very small. Here we assess whether a…
The Be phenomenon, i.e. the ejection of matter from Be stars into a circumstellar disk, has been a long lasting mystery. In the last few years, the CoRoT satellite brought clear evidence that Be outbursts are directly correlated to…
In the past years we have made great efforts to reduce the statistical and systematic uncertainties in stellar parameter and chemical abundance determinations of early B-type stars. Both the construction of robust model atoms for non-LTE…
In astrochemical exploration, infrared (IR) spectroscopy is vital for understanding the composition and structure of ice in various space environments. This article explores the impact of incident angles on IR spectroscopy, focusing on…
Context. Recently our ability to study stars using asteroseismic techniques has increased dramatically, largely through the use of space based photometric observations. Work has also been done using ground based spectroscopic observations…
High-resolution spectroscopic measurements of OB stars are important for understanding processes like stellar evolution, but require labor-intensive observations. In contrast, photometric missions like the Transiting Exoplanet Survey…
Aims. We report theoretical spectral energy distributions (SEDs), Br$\gamma$ line profiles and visibilities for two scenarios that can explain the disk dissipation of active hot stars an account for the transition from the Be to the B…
The advent of space-based photometry missions in the early 21st century enabled the application to asteroseismic data of advanced inference techniques until then restricted to the field of helioseismology. The high quality of the…
CONTEXT: Spectral-line asymmetries and wavelength shifts are signatures of hydrodynamics in solar and stellar atmospheres. Theory may precisely predict idealized lines, but observed spectra are limited by blends, too few suitable lines,…
We analyzed the star HD 171219, one of the relatively bright Be stars observed in the seismo field of the CoRoT satellite, in order to determine its physical and pulsation characteristics. Classical Be stars are main-sequence objects of…
While the effect of rotation on spectral lines is complicated in rapidly-rotating stars because of the appreciable gravity-darkening effect differing from line to line, it is possible to make use of this line-dependent complexity to…
The surfaces of rotating stars serve as a window into their interiors, magnetic dynamos, and are important in other areas including exoplanet discovery and atmospheric characterization. While indirect techniques such as photometry and…
Conventional ground-based optical telescopes, even those with large apertures, primarily observe stars, close binaries, and multiple systems as unresolved point sources through photometric measurements. Spectroscopy can identify multiple…
Spectropolarimetric techniques are a mainstay of astrophysical inquiry, ranging from Solar System objects to the Cosmic Background Radiation. This review highlights applications of stellar polarimetry for massive hot stars, particularly in…