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GT Ursae Majoris AB - a Possible Quadruple System

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

Acta Astronomica

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2018

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Vol. 68, No. 2

141--158

EN

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.

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St 2-22 - Another Symbiotic Star with High-Velocity Bipolar Jets

Tomov T., Zamanov R., Gałan C., Pietrukowicz P.

Acta Astronomica

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2017

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Vol. 67, No. 3

225--242

EN

We report the detection of high-velocity components in the wings of Hα emission line in spectra of symbiotic binary star St 2-22 obtained in 2005. This finding encouraged us to start the present investigation in order to show that this poorly-studied object is a jet-producing system. We have used high-resolution optical and low-resolution near-infrared spectra, as well as available optical and infrared photometry, to evaluate some physical parameters of the St 2-22 components and characteristics of the jets. We confirm that St 2-22 is a S-type symbiotic star. Our results demonstrate that an unnoticed outburst, similar to those in classical symbiotic systems, occurred in the first half of 2005. During the outburst, collimated bipolar jets were ejected by the hot component of St 2-22 with an average velocity of about 1700 km/s.

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Searching for Flickering Variability in Several Symbiotic Stars and Related Objects: BX Mon, V471 Per, RS Oph, V627 Cas, CI Cam, V886 Her, Z And, T CrB, MWC 560, V407 Cyg

Gromadzki M., Mikołajewski M., Tomov T., Bellas-Velidis I., Dapergolas A., Gałan C.

Acta Astronomica

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2006

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Vol. 56, No. 1

97--125

EN

UBVRI photometric observations of 10 symbiotic stars and related objects obtained in the period 2002-2003 are presented. Analyzing differential light curves we found rapid light variations with timescales of tens of minutes and significant amplitudes in the well-known flickers MWC 560, RS Oph, V407 Cyg and T CrB. MWC 560 and V407 Cyg demonstrate quasi periodic oscillations (QPO) with similar amplitudes and timescales. Flickering and unusual flare in V627 Cas as well as some indications of flickering presence in BX Mon are detected. The existence of 29 min oscillations in Z And with an amplitude ≈0.02 mag in the U-band is confirmed. Only one symbiotic star, V471 Per, and both non symbiotic, CI Cam and V886 Her, seem to be constant on flickering timescales. Nevertheless, small night to night changes in the brightness of V886 Her were observed as well.

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HP Lyr - Possibly the Hottest RV Tau Type Object

Graczyk D., Mikołajewski M., Leedjärv L., Frąckowiak S. M., Osiwała J. P., Puss A., Tomov T.

Acta Astronomica

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2002

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Vol. 52, No. 3

293--304

EN

We report Johnson's UBVRI photometric and optical spectroscopic observations of a long period variable HP Lyr which up to now has been considered to be an eclipsing binary with a period of 140 days. Its spectral type changes continuously from A2-3 at maxima to A7-F2 at minima. We propose that the brightness changes are caused by pulsation of the star with two periods: P1=69.35 days, and P2=2×P1=138.7 days. These periods decreased by more than 1% between 1960 and 1980. The spectral luminosity class corresponds to an A type supergiant Iab. HP Lyr is also the optical counterpart of the infrared source IRAS 19199+3950. Relatively high galactic latitude (b=+11°.7) and high radial velocity (-113 km/s) indicate that HP Lyr is an evolved, most likely post-AGB star. All these features suggest that this star is an RV Tau type object.