arXiv subjects

I. F. Bikmaev

Publications and source records attributed to I. F. Bikmaev.

40 records · Page 3Linked to original sources

arXiv2004

Abundance analysis of targets for the COROT / MONS asteroseismology missions II. Abundance analysis of the COROT main targets

One of the goals of the ground-based support program for the COROT and Roemer satellite missions is to characterize suitable target stars for the part of the missions dedicated to asteroseismology. We present the detailed abundance analysis of nine of the potential COROT main targets using the semi-automatic software VWA. For two additional COROT targets we could not perform the analysis due to the high rotational velocity of these stars. For five stars with low rotational velocity we have also performed abundance analysis by a classical equivalent width method in order to test the reliability of the VWA software. The agreement between the different methods is good. We find that it is necessary to measure abundances extracted from each line relative to the abundances found from a spectrum of the Sun in order to remove systematic errors. We have constrained the global atmospheric parameters Teff, log g, and [Fe/H] to within 70-100 K, 0.1-0.2 dex, and 0.1 dex for five stars which are slow rotators (v sin i < 15 km/s). For most of the stars stars we find good agreement with the parameters found from line depth ratios, H-alpha lines, Strömgren indices, previous spectroscopic studies, and also log g determined from the HIPPARCOS parallaxes. For the fast rotators v sin i > 60 km/s it is not possible to constrain the atmospheric parameters.

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arXiv2004

Coordinated INTEGRAL and optical observations of SS433

Results of simultaneous {\it INTEGRAL} and optical observations of galactic microquasar SS433 in May 2003 are presented. The analysis of the X-ray and optical eclipse duration and hard X-ray spectra obtained by {\it INTEGRAL} together with optical spectroscopy obtained on the 6-m telescope allows us to construct a model of SS433 as a massive X-ray binary. X-ray eclipse in hard X-rays has a depth of $\sim 80%$ and extended wings. The optical spectroscopy allows us to identify the optical companion as a A5-A7 supergiant and to measure its radial velocity semi-amplitude $K_v=132$ km/s. A strong heating effect in the optical star atmosphere is discovered spectroscopically. The observed broadband X-ray spectrum 2-100 keV can be described by emission from optically thin thermal plasma with $kT\sim 15-20 keV$

astro-ph↗

arXiv2002

Abundance analysis of two late A-type stars HD 32115 and HD 37594

We have performed abundance analysis of two slowly rotating, late A-type stars, HD 32115 (HR 1613) and HD 37594 (HR 1940), based on obtained echelle spectra covering the spectral range 4000-9850 AAngstrom. These spectra allowed us to identify an extensive line list for 31 chemical elements, the most complete to date for A-type stars. Two approaches to abundance analysis were used, namely a ``manual'' (interactive) and a semi-automatic procedure for comparison of synthetic and observed spectra and equivalent widths. For some elements non-LTE (NLTE) calculations were carried out and the corresponding corrections have been applied. The abundance pattern of HD 32115 was found to be very close to the solar abundance pattern, and thus may be used as an abundance standard for chemical composition studies in middle and late A stars. Further, its H-alpha line profile shows no core-to-wing anomaly like that found for cool Ap stars and therefore also may be used as a standard in comparative studies of the atmospheric structures of cool, slowly rotating Ap stars. HD 37594 shows a metal deficiency at the level of -0.3 dex for most elements and triangle-like cores of spectral lines. This star most probably belongs to the Delta Scuti group.

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arXiv1998

Atmospheric abundances of CP SB2 star components of equal masses. II. 66 Eridani

We report the results of abundance determination for the components of the SB2 star 66 Eri (M_A/M_B=0.97) from high resolution CCD echelle spectra with S/N>=100 taken with the 1-m telescope of Special Astrophysical Observatory (Zelenchuck, Russia). The atmospheric parameters of the components were determined using all available photometric, spectrophotometric and spectral data. The abundances of 27 elements were found. The abundances of components are different. The B component, previously classified as an Hg-Mn star, does not show anomalies typical of this group such as deficit of He, Al and excess of P, Ga, but shows overabundances of heavy elements which amount up to 4-5 dex. The A component also shows moderate Mn and Ba excess. Lines of other heavy elements were not detected. Estimates of upper limits to their abundances do not permit to exclude completely the presence of fainter anomalies in the A component either.

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