Sökning: "chemically peculiar stars"
Visar resultat 1 - 5 av 7 avhandlingar innehållade orden chemically peculiar stars.
1. Investigations of Heavy Elements in Am and HgMn stars
Sammanfattning : The relationship between the HgMn and Am classes of chemically peculiar stars has been investigated primarily by observing abundances of heavy elements, including Pr, Nd, Hg, Tl and Bi. The main objective of the investigation has been to gather observational evidence to provide a better understanding of the mechanisms producing the abundance anomalies of these stars, and to establish the relationship between the two classes. LÄS MER
2. Advances in Stellar Astrophysics from Laboratory Spectroscopy
Sammanfattning : Investigation of astrophysical plasmas, such as stellar atmospheres, require both knowledge of atomic structure and data. We present laboratory instruments, techniques and tools for acquisition of the data required to derive important atomic parameters such as, wavelengths, oscillator strengths and line profiles. LÄS MER
3. Laboratory and Stellar Spectra in High Resolution: Studies of Fe, Pt and Tl in Peculiar Stars
Sammanfattning : The near-infrared spectrum of upsilon Sagittarii has been registered using the SOFIN high resolution spectrometer on the Nordic Optic Telescope, La Palma. For the first time 4f-5g transitions of Fe II in any astrophysical spectrum have been identified. LÄS MER
4. Magnetic fields and chemical maps of Ap stars from four Stokes parameter observations
Sammanfattning : Our knowledge of stellar magnetic fields relies almost entirely on circular polarization observations, which has historically limited our understanding of the stellar magnetic field topologies. Recently, it has become possible to obtain phase-resolved high-resolution spectropolarimetric observations in all four Stokes parameters for early-type magnetic stars. LÄS MER
5. Magnetic and Chemical Structures in Stellar Atmospheres
Sammanfattning : We present an investigation of the magnetic field geometries and inhomogeneous distribution of chemical elements in the atmospheres of peculiar A and B stars. Our study combines high-quality spectroscopic and spectropolarimetric stellar observations with the development and application of novel techniques for theoretical interpretation of the shapes and variability of stellar line profiles. LÄS MER