Carbon deficiencies in the primaries of some classical Algols

The equivalent widths of C II $\lambda$ 4267 \AA line were measured for the mass-gaining primary stars of the 18 Algol-type binary systems. The comparison of the EWs of the gainers with those of the single standard stars having the same effective temperature and luminosity class clearly indicates that they are systematically smaller than those of the standard stars. The primary components of the classical Algols, located in the main-sequence band of the HR diagram, appear to be C poor stars. We estimate $[N_{C} /N_{tot}]$ relative to the Sun as -1.91 for GT Cep, -1.88 for AU Mon and -1.41 for TU Mon, indicating poorer C abundance. An average differential carbon abundance has been estimated to be -0.82 dex relative to the Sun and -0.54 dex relative to the main-sequence standard stars. This result is taken to be an indication of the transferring material from the evolved less-massive secondary components to the gainers such that the CNO cycle processed material changed the original abundance of the gainers. There appear to be relationships between the EWs of C II $\lambda$ 4267 \AA line and the rates orbital period increase and mass transfer in some Algols. As the mass transfer rate increases the EW of the C II line decreases, which indicates that accreted material has not been completely mixed yet in the surface layers of the gainers. This result supports the idea of mixing as an efficient process to remove the abundance anomaly built up by accretion. Chemical evolution of the classical Algol-type systems may lead to constrains on the initial masses of the less massive, evolved, mass-losing stars.Comment: 10 pages, 4 figures, accepted in MNRA

Basic physical properties of the close binary V497 Cep in the open cluster NGC 7160

New light and radial-velocity curves of , a binary in the open cluster NGC 7160, were obtained and the linear ephemeris of the system was refined to {\rm HJD \, (Min\, I)} = (2\,446 \,299.1596\pm0.0064) + (1\fd2028287\pm0\fd0000015) \times E. The first light and radial-velocity curve solutions allowed us to derive the basic physical properties of this astrophysically important binary. It was found that the observed light variation of consists of a strong ellipticity effect and a small contribution from grazing eclipses. A comparison of masses and radii of with theoretical evolutionary tracks indicates that both binary components are very close to the zero-age main sequence. A comparison of disentangled line profiles of the He I 6678 line with synthetic, rotationally broadened line profiles indicates that the rotation of both stars is synchronized with the orbital revolution as expected. This finding increases the credibility of our solutions. We find E(B-V)=0\fm39. The distance to the cluster NGC 7160 was found to be about 760 (± 100) pc which agrees well with other available estimates