Detailed chemical abundances of several CP-stars of the upper main sequence

We present a study of the chemical composition of atmospheres of five stars of the upper main sequence. Investigations of the SB2 system 66 Eri permit to find the gallium spots in atmospheres of the components, the secondary component of the system is a HgMn star, the primary can also be a HgMn star with less pronounced anomalies. The components of the double system HD153720 appear to be metallic-lined stars. A review of studies of the abundance of SB2 systems with A4–F1 components shows that the usually accepted fraction of stars with the solar chemical composition in this region of the HR diagram can be decreased. The abundance patterns of Sirius (>50 elements) in the region of heavy elements give us additional arguments for the hypothesis that not only a diffusion is responsible for the overabundances of these elements in Sirius. The abundance pattern of δ Sct (49 elements) appears to be similar to δ Del type stars, maybe, a subtype of the prototype of one of the largest class of pulsating variables should be changed. The abundance pattern of the Przybylski’s star is the best stellar abundance pattern (after that of the Sun). The possible identification of radioactive elements (84 ≤ Z ≤ 99) in the atmosphere of the Przybylski’s star needs abundance determinations and can be the clue to the understanding of the nature of all CP stars

The abundances of heavy elements in BL138 – red giant of local group fornax dwarf spheroidal galaxy

Using the spectrum obtained with FLAMES/GIRAFFE multi-object spectrograph installed at ESO Very Large Telescope we investigated the absorption lines of heavy elements in the spectrum of BL138. This red giant star belongs to one of the Local Group members – Fornax dwarf spheroidal galaxy. The abundances of 12 stable chemical elements, namely Y, Zr, Nb, Mo, Ru, La, Ce, Pr, Nd, Eu, Dy, Er, Lu, and Hf. The abundance of radioactive elements Ac and Th are also investigated. The analysis of these abundances and also previously published investigation of BL138 allowed claiming that the distribution of abundances is different from that in the solar photosphere. The signs of r-process in the abundance pattern of BL138 are not important. The production of elements from barium to hafnium can be explained by s-process. The abundances of elements from yttrium to ruthenium are lower than it can be expected in the case of s-process synthesis. That is why it can be expected that several nuclear processes took place in the synthesis of these elements. The possibility of detection the actinium absorption line in the spectrum of BL138 clearly indicate the possibility of physical process which results in continuous production of actinium in the atmosphere of BL138. The actinium abundance can be close to logN(Ac)=1.9. It can be the result of hydrogen accretion from interstellar medium on stellar photosphere. The trends of abundances with second ionization potentials of corresponding chemical elements, and also by the emissions in the profiles of hydrogen H α line confirm this identification