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2 2018

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Spectroscopy of the Eclipsing Binary BD-00°2862. Possible Multiplicity

Dimitrov W., Żywucka N, Polińska M., Kamiński K., Kamińska M. K.

Acta Astronomica

2018

Vol. 68, No. 3

269--284

We present the first spectroscopic analysis of the eclipsing binary BD-00°2862. The All Sky Automated Survey light curves yield orbital period of the system of 2.15 d. The shape of the light curve reveals that the components are almost spherical and the binary is detached. The eclipses depths show significant difference of the components' temperature. We acquired spectra with 0.5-m telescope equipped with an echellé spectrograph. The spectra are dominated by the lines of the more luminous component, which is about five times more luminous than its close companion. Obtained radial velocities together with the light curves enabled us to obtain a model of the system using the Wilson-Devinney method. The mass ratio of the stars is 0.67 and the size of the semi-major axis is 8.6 R⊙. The masses of the eclipsing components are M1=1.08±0.03 M⊙ and M2=0.72±0.02 M⊙. The stars are not evolved and the radii are close to the main sequence values: R1=1.21±0.01 R⊙ and R2=0.71±0.01 R⊙. The evolutionary tracks show that the system is probably on the pre main sequence stage. The photometric parallax yields distance of 131 pc, which is comparable with the one obtained by Gaia mission - 130 pc. We carried out a spectrum analysis for the main component obtaining its temperature of 5600±400 K and the metallicity - [M/H]=-0.30±0.20. The star has a visual companion separated by about 12". The companion has proper motion comparable to the one of the main star. Additionally, its distance based on the trigonometric parallax is equal within errors with the distance of component A. Therefore, the companion is probably a part of the system. Its spectral type is M3 and the estimated mass - about 0.3M⊙.

GT Ursae Majoris AB - a Possible Quadruple System

Dimitrov W., Tomov T., Kamiński K., Polińska M., Iliev I., Kamińska M. K.

Acta Astronomica

2018

Vol. 68, No. 2

141--158

We present the first spectroscopic study of an eclipsing system GT UMa. Our spectra show that the main visual component A is a triple-lined star, which consists of a close eclipsing pair and a farther third component. Radial velocity measurements show evidence of reflex motion. We used Hipparcos and our own R-band light curves for the analysis. These results enabled us to calculate absolute parameters of the eclipsing binary system: 1.37 M⊙ and 1.31 M⊙ and corresponding radii 2.11 R⊙ and 1.63 R⊙. Both eclipsing components are evolved. The orbital period of the eclipsing subsystem is 1.2 d and the semi-major axis - 6.5 R⊙. The wide orbit has low radial velocity amplitude and its parameters are difficult to determine. We obtained a preliminary solution which must be confirmed with future observations. The preliminary period of the wide orbit is 394 d and the lower limit for the semi-major axis - 174 R⊙ (0.81 a.u.). We estimated the mass of the third body to about 1.1 M⊙. Additionally, we investigated the visual companion B. We obtained spectra of this star and measured the radial velocity which is very close to the one of the component A. The proper motions and the parallax are also similar. These are strong arguments that component B is gravitationally bound with the main triple system A.