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We report on a chemical-abundance analysis of two very metal-poor horizontal-branch stars in the Milky Way halo: CS 22186-005 ([Fe/H] = -2.70) and CS 30344-033 ([Fe/H] = -2.90). The analysis is based on high-resolution spectra obtained at ESO, with the spectrographs HARPS at the 3.6m telescope, and UVES at the VLT.We adopted one-dimensional, plane-parallel model atmospheres assuming local thermodynamic equilibrium. We derived elemental abundances for 13 elements for CS 22186-005 and 14 elements for CS 30344-033. This study is the first abundance analysis of CS 30344-033. CS 22186-005 has been analyzed previously, but we report here the first measurement of nickel (Ni; Z = 28) for this star, based on twenty-two Ni i lines ([Ni/Fe] = -0.21 ± 0.02); the measurement is significantly below the mean found for most metal-poor stars. Differences of up to 0.5 dex in [Ni/Fe] ratios were determined by different authors for the same type of stars in the literature, which means that it is not yet possible to conclude that there is a real intrinsic scatter in the [Ni/Fe] ratios. For the other elements for which we obtained estimates, the abundance patterns in these two stars match the Galactic trends defined by giant and turnoff stars well. This confirms the value of horizontal-branch stars as tracers of the chemical properties of stellar populations in the Galaxy. Our radial velocities measurements for CS 22186-005 differ from previously published measurements by more than the expected statistical errors. More measurements of the radial velocity of this star are encouraged to confirm or refute its radial velocity variability. [ABSTRACT FROM AUTHOR]

Abstract: Photoelectric BVR light curves of the recently discovered eclipsing binary V351 Peg were studied for the first time to derive the physical parameters of the system. The light curves were obtained at the TU¨BİTAK National Observatory (TUG) during three nights in August 2003. The solutions made by using Djurašević’s inverse-problem method describe the V351 Peg system as an overcontact configuration (fover∼21%) with a very small temperature difference between the components (ΔT=Th−Tc∼21 K). Having in mind large difference in their masses, this suggests a good thermal contact between the components, i.e. a significant energy transfer from the more massive primary onto the less massive secondary. The bright area on the less massive star, near the neck region of the common envelope, can be taken as a consequence of this energy exchange between the components. Roche model with this bright active region on the less massive star successfully fits the observations. The relatively small amplitude of light curves arises from partial eclipse caused by the low orbital inclination (i∼63°). The stellar temperatures (Th∼7580 K and Tc∼7560 K) and the estimated values of the gravity-darkening exponents (βh∼0.20 and βc∼0.18) indicate that there is a mixture of radiative and convective transport of energy. [Copyright &y& Elsevier]

Photoelectric UBV light curves of the recently discovered eclipsing binary V776 Cas were studied for the first time to derive the physical parameters of the system. The light curves were obtained at the TU¨BI˙TAK National Observatory (TUG) during 8–9 October 2002. Due to the proximity of the visual companion the light curves were contaminated by the third light effect which has a relatively small impact on the system parameters estimation. This effect dominantly changes only the degree of overcontact and orbit inclination. The solutions made by using Djurasˇevic's inverse-problem method describe the V776 Cas system as a high overcontact configuration (fover∼41% without, and 55% and 58% with two different values of the third light effect – L3=0.091 and L3=0.136) with a relatively small temperature differences between the components. Because of the large difference in masses of the components (q=mc/mh=0.13) these solutions suggest a significant mass and energy transfer from the hotter – more massive primary onto the cooler – less massive secondary through the connecting neck of the common envelope. The obtained orbital inclination (i∼53∘.9 without, and i∼55∘ and i∼56∘ with two different values of the third light effect – L3=0.091 and L3=0.136) explains the characteristic shape of the light curves with a relatively small amplitude which is due to partial eclipses of the components in both of the photometric minima. [Copyright &y& Elsevier]

A period study of the binary system TX Her based on the extensive series of minima times covering almost a century (95 years) indicates the periodic O–C variation for the system. This continuous oscillatory variation covers two maxima, about 16 800 orbital periods, by the present observational data. It can be attributed to the light-time effect due to a third body with a period of 51.47 ± 0.27 years in the system. The analysis yields a light-time semi-amplitude of 0.0143 ± 0.0003 days and an orbital eccentricity of 0.81 ± 0.02. Adopting the total mass of TX Her, the mass of the third body assumed in a co-planar orbit with the binary is M3=0.48±0.02M⊙ and the semi-major axis of its orbit is a3=18.32±0.21 AU. [Copyright &y& Elsevier]