14 research outputs found
Probing the Przybylski star for Deuterium
The Przybylski star spectrum has been studied in order to search for
deuterium lines. Since this star is extremely enriched in the s-process
elements, which are the product of interaction between free neutrons and seed
nuclei, we might as well expect to detect deuterium in this star. However, no
visible spectroscopic manifestation of deuterium has been detected. Perhaps,
the reason of this result is the convective "destruction" of this isotope.Comment: 4 pages, 2 figures, accepted to Astronomische Nachrichte
An enigma of Przybylski's star: is there promethium on its surface?
We carried out a new attempt to check for the presence promethium lines in
the spectrum of HD101065 (Przybylski's star). The neutron capture element
promethium does not have stable isotopes and the maximum half-life time is
about 18 years. Thus its presence in this peculiar star would indicate an
ongoing process of irradiation of its surface layers with free neutrons.
Unfortunately, almost all promethium lines are heavily blended with lines of
other neutron capture elements and other species. We selected and analysed
three lines of promethium (Pm I and Pm II) and came to the conclusion that at
present it is impossible to definitely claim the presence of this element in
Przybylski's star atmosphere.Comment: Accepted for publication in Astronomische Nachrichte
The Chemical Composition of HD47536: A Planetary Host Halo Giant with Possible λ Bootis Features and Signs of Interstellar Matter Accretion
We investigated the chemical composition of the planetary host halo star HD47536 via high-resolution spectral observations
recorded using a 1.5 meter Cerro Tololo Inter-American Observatory (CTIO) telescope (Chile). Furthermore, we determined
the abundances of 38 chemical elements. Both light and heavy elements were overabundant compared to the iron group
elements. The abundance pattern of HD47536 was similar to that of halo-type stars, with an enrichment of heavy elements.
We analyzed the relationships between the relative abundances of chemical elements and their second ionization potentials
and condensation temperatures. We demonstrated that the interplay of charge-exchange reactions owing to the accretion
of interstellar matter and the gas-dust separation mechanism can influence the initial abundances and can be used to
qualitatively explain the abundance patterns in the atmosphere of HD47536
Li abundances and chromospheric activity of BY Dra type stars
Atmospheric parameters and Li abundances have been determined for 162 stars observed at high resolution, high signal to noise ratio with the ELODIE echelle spectrograph (OHP, France). Among them, about 70 stars are active stars with a large fraction of BY Dra type stars. For all stars, rotational velocities were obtained with a calibration of the cross-correlation function, effective temperatures by the line depth ratio method, surface gravities by the parallaxe method and by the ionization balance of iron. The frequency of stars with observed lithium is significantly higher in active stars than in non active stars. Among active stars, no clear correlation has been found between different indicators of activity for our sample stars, but some correlation of an index R′H K and vsini is observed