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A spectroscopic study of the Algol-type binaries S Equulei and KO Aquilae: absolute parameters and mass transfer
We present and analyse high-resolution optical spectra of two Algolbinaries, namely S Equ and KO Aql, obtained with the echellespectrograph at Catania Astrophysical Observatory. New accurate radialvelocities (RVs) for the hotter primary components are obtained. Thanksto the cross-correlation procedure, we were able to measure, for thefirst time to our knowledge, RVs also for the cool secondary componentsof S Equ and KO Aql. By combining the parameters obtained from thesolution of the RV curves with those obtained from the light-curveanalysis, reliable absolute parameters of the systems have been derived.The rotational velocity of the hotter components of S Equ and KO Aql hasbeen measured and it is found that the gainers of both systems rotateabout 30 per cent faster than synchronously. This is likely due to masstransfer across the Lagrangian L1 point from the cooler tothe hotter component. The lower luminosity of the mass-gainingcomponents of these systems compared to normal main-sequence stars ofthe same mass can also be an effect of the mass transfer. The Hαprofiles were analysed with the `synthesis and subtraction' techniqueand reveal clear evidence of mass transfer and accretion structures. Inboth systems, especially before the primary eclipses and afterwards, weclearly observed extra absorption lines. From the integrated absorptionand the RV variations of these features, we found that the massaccretion is very dense around the impact region of the hottercomponents. A double-peaked emission in the spectra of S Equ was seenoutside the eclipses. One of these peaks is likely originated in aregion between the centre of mass and the cooler component, which isoccupied by the flowing matter. Furthermore, the Hα differencespectra of S Equ and KO Aql also display emission features, which shouldbe arising from the magnetic activity of the cooler components.Based on observations collected at the Catania Astrophysical Observatory(Italy).E-mail: fsoydugan@comu.edu.tr
| A large, complete, volume-limited sample of G-type dwarfs. I. Completion of Stroemgren UVBY photometry
Four-colour photometry of potential dwarf stars of types G0 to K2,selected from the Michigan Spectral Catalogues (Vol. 1-3), has beencarried out. The results are presented in a catalogue containing 4247uvby observations of 3900 stars, all south of δ = -26deg. Theoverall internal rms errors of one observation (transformed to thestandard system) of a program star in the interval 8.5 < V < 10.5are 0.0044, 0.0021, 0.0039, and 0.0059, respectively, in V, b-y, m_1_ ,and c_1_. The purpose of the catalogue, combined with earliercatalogues, is to allow selection of a large, complete, volume-limitedsample of G- and K-type dwarfs, investigate their metallicitydistribution, and compare it to predictions of various models ofgalactic chemical evolution. Future papers in this series will discussthese subjects.
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Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Karina |
| Sað Açýklýk: | 10h35m30.01s |
| Yükselim: | -74°36'01.0" |
| Görünürdeki Parlaklýk: | 8.743 |
| Uzaklýk: | 383.142 parsek |
| özdevim Sað Açýklýk: | -43.2 |
| özdevim Yükselim: | 4.1 |
| B-T magnitude: | 10.912 |
| V-T magnitude: | 8.923 |
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