Angelina V. Shavrina

The spectrum of the roAp star HD 101065 (Przybylski's star) in the Li I 6708 A spectral region

We carried out a detailed analysis of spectra of the unique roAp star HD 101065 (Przybylskis star) near the resonance doublet Li I 6708 A, using a most complete line list including all possible transitions between REE levels of the NIST database. Our model calculations were performed under two assumptions: a blend of Li and REE lines, and a blend of REE lines only. They prove that Li lines are present in the range 6707.72−6708.02 A and that the resulting Li abundance is 3.1 dex (in the scale log N(H) = 12.0), while the isotopic ratio 6 Li/ 7 Li is near to 0.3.

On the radioactive shells in peculiar main sequence stars: the phenomenon of Przybylski's star.

Using high-dispersion spectral observations of HD 101065 (Przybylskis star) we have identified the lines of heavy radioactive elements with atomic numbers from 84 to 99 in the spectrum of the star. We found the lines of all these elements except At (Z=85) and Fr (Z=87). We try to explain a presence of such heavy species in the atmosphere of this star as a result of radioactive decay of Th and U nuclei and neutron capture process producing some transuranium isotopes. The necessary conditions for these processes to work may appear due to atomic diffusion and favorable accumulation of the thorium and uranium nuclei in the upper of the PS atmosphere. To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Lithium and the 6Li-7Li isotope ratio in the atmospheres of some sharp-lined roAp stars

The λ 6708 Å and 6103 Å lithium lines in the high-resolution spectra of some sharp-lined roAp stars are analyzed using three spectral-synthesis codes STARSP, ZEEMAN2, and SYNTHM. The lines from the VALD database were supplemented with lines of rare-earth elements from the DREAM database and new lines calculated using the NIST energy levels. Our synthetic-spectrum calculations take into account magnetic splitting and other line-broadening effects. Lithium overabundances were found in the atmospheres of the stars based on our analysis of both lithium lines, along with high values of the 6Li-7Li isotope ratio (0.2–0.5). This can be explained if lithium is produced in spallation reactions and the surface 6Li and 7Li is preserved by strong magnetic fields in the upper layers of the stellar atmospheres, around the poles of the dipole field. The asymmetry of lithium lines to the red may be due to the action of shocks in the optically thin upper atmosphere, with the shocked material subsequently falling onto the star.

Lithium and its isotopic ratio

The lines of lithium at

^6{\rm Li}/^7{\rm Li}

\lambda 6708

in the atmospheres of some sharp-lined roAp stars

and

ATMOSPHERIC OZONE PROFILES DURING VASYLKIV OIL BURNING EPISODE

\lambda 6103

The Nature of Magnetic Chemically Peculiar Stars Through the Prism of Inexplicable Facts

are analyzed in high resolution spectra of some sharp-lined and slowly rotating roAp stars. Three spectral synthesis codes, STARSP, ZEEMAN2 and SYNTHM were used. New lines of the Rare Earth Elements from the DREAM database, and lines calculated on the basis of the NIST energy levels were included. Magnetic splitting and other line broadening processes were taken into account. Enhanced abundances of lithium in the atmospheres of the stars studied are obtained for both lithium lines. High estimates of

The chemical compositions and surface structures of two roAp stars with lithium spots (HD 83368 and HD 60435)

^6{\rm Li}/^7{\rm Li}

Structure of the atmosphere of the magnetic star hd21699

ratio (