Alexander V. Yushchenko

Rotational Velocities of the Components of 23 Binaries

By using high dispersion spectra obtained by the 1.8 m telescope of Bohyunsan Optical Astronomy Observatory (South Korea), multiline least-square deconvolution of line profiles, and Fourier analysis techniques, we obtained the rotational velocities of the components of 23 binary systems. The rotational velocities for nine primary, eight secondary, and one tertiary components of these systems were determined for the first time. The rotational velocities for primary components of seven systems appeared to be significantly different than the corresponding synchronous values (more than twice as fast for five systems, and less than half as fast for two systems). Our velocities for AU Mon, RY Gem, and RZ Eri are significantly lower than the previously published values obtained by using one or very few lines. We show that these discrepancies can be explained by strong blending of the lines in the spectra of the primaries with strong lines of the secondaries, by influence of gaseous streams, and maybe by nonsolar chemical compositions.

Thorium-rich halo star HD 221170: Further evidence against the universality of the r-process ,

We report the abundance determination in the atmosphere of the bright halo star HD 221170. The spectra were taken with the Terskol Observatorys 2.0-m telescope with a resolution R = 45 000 and signal-to-noise ratio up to 250 in the wavelength region 3638-10 275 A. The adopted atmospheric parameters correspond to an effective temperature Teff = 4475 K, a surface gravity log g = 1.0, a microturbulent velocity vmicro = 1.7 km s −1 , and a macroturbulent velocity vmacro = 4k m s −1 . The abundances of 43 chemical elements were determined with the method of spectrum synthesis. The large overabundances (by 1 dex relative to iron) of elements with Z > 38 are shown to follow the same pattern as the solar r-abundances. The present HD 221170 analysis confirms the non-universality of the r-process, or more exactly the observation that the astrophysical sites hosting the r-process do not always lead to a unique relative abundance distribution for the bulk Ba to Hg elements, the Pb-peak elements, and the actinides.

Atomic data for radioactive elements Ra I, Ra II, Ac I and Ac II and application to their detection in HD 101065 and HR 465

Radiative data for transitions of astrophysical interest in radioactive elements Ra I, Ra II, Ac I and Ac II have been computed using a semi-empirical relativistic Hartree-Fock approach including core polarization effects. Most of the oscillator strengths reported in the present paper are new. A possible detection of radium (Ra II) and actinium (Ac II) in the spectrum of the stars HD 101065 and HR 465 is examined and discussed.

CHEMICAL ABUNDANCE PATTERNS FOR SHARP-LINED STARS

In order to increase the completeness of the investigations of stellar abundances, we can use spectrum synthesis method, new atomic data and observation of stellar spectra with resolution comparable to solar spectral atlases. We made a brief review of main problems of these three ways. We present new results of abundance determinations in the atmospheres of four stars. The first is the implementation of new atomic data to well known Przybylski`s star. We show that the number of spectral lines, which can be identificated in the spectrum of this star, can be significantly higher. The second example is the investigation of Cyg. We found the abundances of 51 elements in the atmosphere of this mild barium star. The third example is halo star HD221170. Our preliminary abundance pattern consists of 42 elements. The heaviest elements in this pattern are U and Th. The last star is the spectroscopic binary HD153720. The number of elements investigated in the spectra of components of this star is not large, but the results show that the components are Am-stars.

A high-resolution spectral atlas of α persei from 3810 to 8100 Å

We present a high-resolution (λ/δλ = 90,000) spectral atlas of the F5 Ib star α Per covering the 3810-8100 A region. The atlas, based on data obtained with the aid of the echelle spectrograph BOES fed by the 1.8 m telescope at Bohyunsan Observatory (Korea), is the result of the co-addition of a few well-exposed spectra. The final signal-to-noise ratio is ~800 at ~6000 A. The atlas is compared with a synthetic spectrum computed using a code based on Kurucz software and databases. The adopted model atmosphere parameters are Teff = 6240 ± 20 K, log g = 0.58 ± 0.04, and vmicro = 3.20 ± 0.05 km s–1. We also derived an iron abundance of [Fe/H] = -0.28 ± 0.06. The spectral lines of α Per have been identified by matching the synthetic spectrum with the observed one. The atlas is presented in figures and available in digital form on the World Wide Web, along with the synthetic spectrum and spectral line identification tables.

HD 153720 - A SB2 system with twin metallic-line components

We report the results of abundance determinations for the components of the SB2 star HD 153720 from high resolution (R = 60 000) echelle high signal-to-noise spectra of the wavelength region 3595-10 260 A taken with the 2.7 m telescope of the McDonald Observatory We found the values of the atmospheric parameters of the primary to be effective temperature T eff = 7425 K and surface gravity log g = 4.0 cgs, and of the secondary to be T eff = 7125 K and log g = 3.9 cgs. The microturbulent velocity is υ micro = 2.7 km s -1 for both components, and the projected rotational velocity is υ sin i = 15 km s -1 also for both components. The abundances of about 20 elements were determined with the method of spectrum synthesis. The components of HD 153720 are metallic-line stars. Possible inconsistencies between old and new measurements of radial velocities may be explained by the existence of third body in this system. A review of recent high resolution spectral observations of eight A4-F1 binaries shows that only one of these systems can be classified as normal.

Atmospheric chemical composition of the halo star HD 221170 from a synthetic-spectrum analysis

The atmospheric abundances of 30 chemical elements in the halo star HD 221170 are analyzed by fitting synthetic spectra to observed spectra (i) with a resolution of 60 000 and signal-to-noise ratios of about 200 taken with the 1.93-m telescope of the Observatoire de Haute Provence and (ii) with a resolution of 35 000 and signal-to-noise ratios of more than 100 taken with the 2-m telescope of the Terskol Peak Observatory. The derived parameters of the stellar atmosphere are Teff=4475 K, log g=1.0, [Fe/H]=−2.03, Vmicro=1.7 km/s, and Vmacro=4 km/s. The parameters Teff, log g, [Fe/H], and Vmicro can be determined by analyzing the variations of the rms error of the mean iron abundance derived using different model atmospheres. The chemical composition of the star’s atmosphere is analyzed. The abundances of a total of 35 elements in HD 221170 have been derived in this paper and in previous studies. Overall, the abundances of elements lighter than praseodymium are consistent with the elemental abundances in the atmospheres of stars with similar metal deficits. Copper and manganese are underabundant by −2.9 and −2.6 dex, respectively, relative to the Sun (when the analysis includes the effects of hyperfine structure). Heavy r-process elements (starting from praseodymium) are overabundant compared to iron-group elements. This can be explained by an enrichment in r-process elements of the material from which the star was formed.

Chemical Composition of the Components of Eclipsing Binary Star ZZ Bootis

We investigated ZZ Boo using a high-resolution (R = 80,000) spectrum obtained at the BOES echelle spectrograph attached to a 1.8?m telescope at the Bohuynsan observatory in Korea. The atmospheric parameters of the components were found using the published photometrical observations and the abundance analysis of iron lines: the flux ratio of the components FA /FB = 1.12 ? 0.15, the effective temperatures of the components T eff = 6860 ? 20?K and 6930 ? 20?K, the surface gravities log g = 3.72 ? 0.10 and 3.84 ? 0.10, the metallicities [Fe/H] = ?0.10 ? 0.08 and ?0.03 ? 0.10, and the projected rotation velocities vsin i = 11.9 ? 0.4?km?s?1 and 19.3 ? 0.8?km?s?1 for the primary and secondary components, respectively. The pointed errors are the formal errors of the methods used; the systematic errors of the temperatures, gravities, metallicities, and projected rotational velocities can be as high as 250-300?K, 0.3?dex, 0.15?dex, and 4?km?s?1, respectively. The abundances of 24 and 22 chemical elements were determined in the atmospheres of the components. The abundance pattern of the primary component shows the solar or slightly undersolar abundances of all elements. CNO abundances are close to solar values. The abundance pattern of this component resembles those of ? Boo type stars. The abundances of light elements, except oxygen, in the atmosphere of the secondary component are practically solar. The abundances of barium and two detected lanthanides are close to the solar values; the overabundance of oxygen is 0.9?dex. The abundances of two components are evidently different. The comparison of relative abundances with the condensation temperatures and second ionization potentials of the elements confirms the difference in abundance patterns and allows discussion of the different accretion scenarios for two components of this binary system.

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

TIME-SERIES SPECTROSCOPY OF THE ECLIPSING BINARY Y CAM WITH A PULSATING COMPONENT

We present the physical properties of the semi-detached Algol-type eclipsing binary Y Cam based on high resolution spectra obtained using the Bohyunsan Optical Echelle Spectrograph. This is the first spectroscopic monitoring data obtained for this interesting binary system, which has a δ Sct-type pulsating component. We obtained a total of 59 spectra over 14 nights from 2009 December to 2011 March. Double-lined spectral features from the hot primary and cool secondary components were well identified. We determined the effective temperatures of the two stars to be Teff,1 = 8000 ± 250 K and Teff,2 = 4629 ± 150 K. The projected rotational velocities are v1sin i1 = 51 ± 4 km s−1 and v2sin i2 = 50 ± 10 km s−1, which are very similar to a synchronous rotation with the orbital motion. Physical parameters of each component were derived by analyzing our radial velocity data together with previous photometric light curves from the literature. The masses and radii are M1 = 2.08 ± 0.09 M⊙, M2 = 0.48 ± 0.03 M⊙, R1 = 3.14 ± 0.05 R⊙, and R2 = 3.33 ± 0.05 R⊙, respectively. A comparison of these parameters with the theoretical evolution tracks showed that the primary component is located between the zero-age main sequence and the terminal-age main sequence, while the low-mass secondary is noticeably evolved. This indicates that the two components have experienced mass exchange with each other and the primary has undergone an evolution process different from that of single δ Sct-type pulsators.