Related papers: The unusual A-star VW Ari: chemical composition re…
A spectroscopic study was carried out for the double-line A-type eclipsing binary system RR Lyn A+B based on the disentangled spectra, with an aim of clarifying the differences in photospheric chemical compositions between the components,…
Our goal is to find new candidate lambda Boo stars that belong to binary systems. A detailed abundance determination of some candidates could confirm their true lambda Boo nature, while the composition of eventual late-type companions could…
AR Aur A+B is a close binary of astrophysical interest, because dissimilar surface compositions are reported between similar late B-type dwarfs. A new spectroscopic study on this system was carried out based on the disentangled spectra, in…
A spectroscopic study was carried out on the surface chemical abundances of CNO and several heavier elements in the primary and secondary components of 5 eclipsing close binaries around A-type (AR Aur, beta Aur, YZ Cas, WW Aur, and RR Lyn),…
Eclipsing binary systems are unique stellar objects to examine and understand the stellar evolution and the formation. Thanks to these systems, the fundamental stellar parameters (mass, radius) can be obtained very precisely. The existence…
The secondary of the famous young binary RW Aur is much less studied than the primary. To compensate this shortcoming, we present here the results of UBVRIJHK photometric, VRI polarimetric and optical spectral observations of RW Aur B. The…
We investigate the stellar atmospheres of the two components of the Herbig Ae SB2 system AK Sco to determine the elements present in the stars and their abundance. Equal stellar parameters T_eff = 6500K and log g = 4.5 were used for both…
High-resolution and high S/N CCD spectra were analyzed to determine accurate LTE abundances in four lambda Boo stars: pi^1 Ori, 29 Cyg, HR 8203 and 15 And. In general, 14 chemical elements were investigated. The main results are the…
The selective abundance of C, N, O (almost solar) with respect to that of other elements (underabundant) in lambda Boo stars has been interpreted as a characteristic peculiarity of these objects, when considered as single stars. We show…
High angular resolution observations have shown that some stars classified as lambda Boo are binaries with low values of angular separation and magnitude difference of the components; therefore the observed spectrum of these objects is a…
The photospheres of about 10-20% of main sequence A- and B-type stars exhibit a wide range of chemical peculiarities, often associated with the presence of a magnetic field. It is not exactly known at which stage of stellar evolution these…
Abundance analyses from high-resolution optical spectra are presented for 19 Type II Cepheids in the Galactic field. The sample includes both short-period (BL Her) and long-period (W Vir) stars. This is the first extensive abundance…
Since Baschek & Slettebak (1988) drew attention to the similarity between the abundance pattern of lambda Boo stars and that of Vega, there has been a long debate whether Vega should be listed among the chemically peculiar stars of lambda…
A spectroscopic investigation of the lithium resonance doublet in $\xi$ Boo A and $\xi$ Boo B in terms of both abundance and isotopic ratio is presented. We obtained new $R$=130\,000 spectra with a signal-to-noise ratio (S/N) per pixel of…
The $\lambda$ Boo stars are chemically peculiar A-type stars whose abundance anomalies are associated with the accretion of metal-poor material. We searched for $\lambda$ Boo stars in the southern hemisphere in a targeted spectroscopic…
Our aim is to test the accretion scenario of lambda Boo stars. This model predicts that a binary system with two early-type stars passing through a diffuse cloud should both display the same superficial peculiarity. We carried out a…
AR Aur is a detached eclipsing binary containing two late-B stars which are chemically peculiar, on a circular orbit of period 4.135 d. The primary is a HgMn star which shows temporal changes in its chemical abundances and spectral line…
Chemical compositions are derived from high-resolution spectra for five field SRd variables. These supergiants not previously analysed are shown to be metal-poor: KK Aql with [Fe/H] = -1.2, AG Aur with [Fe/H] = -1.8, Z Aur with [Fe/H] =…
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,…
Context. A significant number of the Wolf-Rayet stars seem to be binary or multiple systems, but the nature of many of them is still unknown. Dedicated monitoring of WR stars favours the discovery of new systems. Aims. We explore the…