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GT Ursae Majoris AB - a Possible Quadruple System

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

tom 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.

Curious Variables Experiment (CURVE). RZ LMi - the Most Active SU UMa Star

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Olech A. , Wiśniewski M. , Złoczewski K. , Cook L. M. , Mularczyk K. , Kędzierski P.

tom Vol. 58, No. 2

131--152

We report extensive photometry of the frequently outbursting dwarf nova RZ Leo Minoris. During two seasons of observations we detected 12 superoutbursts and 7 normal outbursts. The V magnitude of the star varied in range from 16.5 mag to 13.9 mag. The superoutbursts occur quite regularly flashing every 19.07(4) days and lasting slightly over 10 days. The average interval between two successive normal outbursts is 4.027(3) days. The mean superhump period observed during the superoutbursts is Psh=0.059396(4) days (85.530±0.006 min). The period of the superhumps was constant except for one superoutburst when it increased with a rate of P/Psh=7.6(1.9)×10-5. Our observations indicate that RZ LMi enters the stage of permanent superhumps, both in superoutbursts and quiescence. This may indicate that decoupling of thermal and tidal instabilities play important role in ER UMa systems. No periodic light variations which can be connected with orbital period of the binary were seen, thus the mass ratio and evolutionary status of RZ LMi are still unknown.