Jílové u Prahy, Czech Republic
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Zasche P.,Charles University | Svoboda P.,Private Observatory | Uhlar R.,Private Observatory
Astronomy and Astrophysics | Year: 2012

Context. A study of late-type low-mass eclipsing binaries provides us with important information about the most common stars in the Universe. Aims. We obtain the first light curves and perform period analyses of two neglected eclipsing binaries GK Boo and AE For to reveal their basic physical properties. Methods. We performed both a period analysis of the times of the minima and a BVR light curve analysis. Many new times of minima for both the systems were derived and collected from the data obtained by automatic and robotic telescopes. This allowed us to study the long-term period changes in these systems for the first time. From the light curve analysis, we derived the first rough estimates of the physical properties of these systems. Results. We find that the analyzed systems are somewhat similar to each other. Both contain low-mass components of similar types, both are close to the Sun, both have short orbital period, and both contain another low-mass companions on longer orbits of a few years. In the case of GK Boo, both components are probably of K3 spectral type, while the distant companion is probably a late M star. The light curve of GK Boo is asymmetric, which probably causes the shift in the secondary minima in the O-C diagram. System AE For comprises two K7 stars, and the third body is a possible brown dwarf with a minimal mass of only about 47 M Jup. Conclusions. We succeed in completing period and light curve analyses of both systems, although a more detailed spectroscopic analysis is needed to confirm the physical parameters of the components to a higher accuracy. © 2012 ESO.


Zasche P.,Charles University | Wolf M.,Charles University | Uhlar R.,Private Observatory | Kucakova H.,Charles University | Kucakova H.,VSB - Technical University of Ostrava
Astronomical Journal | Year: 2014

The minimum timings of eclipsing binaries V418 Aql, SU Boo, RV CVn, CR Cas, GV Cyg, V432 Per, and BD+42 2782 were collected and analyzed. Their long-term behavior was studied via period analysis, revealing a periodic term in eclipse times. We derived 576 new times of minimum. Hence, to describe the periodic variation, a third-body hypothesis was proposed and the resulting orbital periods are as follows: 70, 7.4, 53, 37, 27, 53, and 18 yr, respectively. For the system V432 Per an additional 9.5 yr variation was also found. The predicted minimum masses of these distant bodies were calculated and their detectability discussed. The light curves of SU Boo and RV CVn were analyzed using the PHOEBE program, resulting in physical parameters of the components. New variable stars in the field of V418 Aql were discovered. © 2014. The American Astronomical Society. All rights reserved..


Zasche P.,Charles University | Uhlar R.,Private Observatory
Monthly Notices of the Royal Astronomical Society | Year: 2013

More than three hundred years ago, Ole Rømer measured the speed of light purely by observing the periodic shift of the observed eclipse arrival times of Jupiter's moons arising from the varying Earth-Jupiter distance. The same method of measuring the periodic modulation of delays is still used in astrophysics. The ideal laboratories for this effect are eclipsing binaries. The unique system V994 Her consists of two eclipsing binaries orbiting each other. However, until now it was not certain whether these were gravitationally bound and what their orbital period was. We show that the system is in fact quintuple and the two eclipsing binaries are orbiting each other with a period of about 6.3 yr. This analysis was performed only through studying the periodic modulation of the two periods: during the periastron passage one binary has an apparently shorter period, while the other one is longer, exactly as required by theory. Additionally, it was found that both inner eclipsing pairs orbit with slightly eccentric orbits, undergoing slow apsidal motion with a period of the order of centuries. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.


Zasche P.,Charles University | Uhlar R.,Private Observatory
Astronomy and Astrophysics | Year: 2010

Aims. We present the detailed analysis of triple system KR Com with different observational techniques - photometry, interferometry, and period variation. Methods. The use of BVR photometry of the close-contact binary KR Com, which is the primary component of a triple system, helps us to better describe the properties of the components. The interferometric data obtained during the last 30 years sufficiently determine the visual orbit, but the use of minima timings of KR Com for the study of period variation together with the visual orbit is a novel approach in this system. Results. Basic physical parameters resulting from the light curve analysis agree well with the previous results from spectroscopy. The temperatures for the primary and secondary component resulted in 5549 and 6072 K, respectively, and the amount of the third light in all filters is about 1/3 of the total luminosity. The distant third component revolves around the common barycenter on 11 yr orbit with a very high eccentricity (0.934) and this movement is also detectable via the period variation, which is clearly visible in the O-C diagram of times of minima observations. The use of minima times for the combined analysis helps us to independently determine the distance to the system (64.02 ± 9.42 pc) and also to confirm the orientation of the orbit in space. Conclusions. New minima observations and also spectroscopy would be very profitable, especially during the next periastron passage in the year 2017. © 2010 ESO.


Wolf M.,Charles University | Zasche P.,Charles University | Kucakova H.,VSB - Technical University of Ostrava | Lehky M.,Astronomical Society Hradec Kralove | And 3 more authors.
Astronomy and Astrophysics | Year: 2013

Aims. As part of the long-term Ondřejov and Ostrava observational projects, we aim to measure the precise times of minimum light for eccentric eclipsing binaries, needed for accurate determination of apsidal motion. Over fifty new times of minimum light recorded with CCD photometers were obtained for five early-type and eccentric-orbit eclipsing binaries: V785 Cas (P = 2. d70, e = 0.09), V821 Cas (1.d77, 0.14), V796 Cyg (1. d48, 0.07), V398 Lac (5.d41, 0.23), and V871 Per (3. d02, 0.24). Methods. O-C diagrams of binaries were analysed using all reliable timings found in the literature, and new elements of apsidal motion were obtained. Results. We derived for the first time or improved the relatively short periods of apsidal motion of about 83, 140, 33, 440, and 70 years for V785 Cas, V821 Cas, V796 Cyg, V398 Lac, and V871 Per, respectively. The internal structure constants, log k2, for V821 Cas and V398 Lac are then found to be-2.70 and-2.35, under the assumption that the component stars rotate pseudosynchronously. The relativistic effects are weak, up to 7% of the total apsidal motion rate. © 2013 ESO.


Wolf M.,Charles University | Kotkova L.,Czech Republic Astronomical Institute | Kocian R.,VSB - Technical University of Ostrava | Dreven R.,Private Observatory | Hanzl D.,Private Observatory
Astronomical Journal | Year: 2010

WW Camelopardalis is a relatively bright eclipsing binary system with a slightly eccentric orbit. A dozen of its new eclipse times were measured as part of our long-term observational project of eccentric eclipsing binaries. Based on a new solution of the current O - C diagram, we found for the first time an apsidal motion in good agreement with theory. Its period is about 370 ± 50 years. The determined internal structure constant is close to the theoretically expected value. The relativistic effect is significant, being about 13% of the total apsidal motion rate. © 2010. The American Astronomical Society.


Zasche P.,Charles University | Svoboda P.,Private Observatory | Slechta M.,Czech Republic Astronomical Institute
Monthly Notices of the Royal Astronomical Society | Year: 2012

The main aim of this paper is the first detailed analysis of multiple system V2083 Cyg, to reveal its basic physical properties. The system was studied using the methods of light-curve and radial-velocity curve analysis, together with interferometric data from the visual pair obtained during the last century. It was found that the close subsystem contains two very similar stars of spectral type A7-8. Moreover, a third body is orbiting around this pair with a period of about 177yr. Due to the discrepancy in the total mass derived with the two methods, the possibility arises that the third body is perhaps also a binary, or some object with lower luminosity but higher mass than a normal main-sequence star. Another explanation is that the Hipparcos value of parallax is incorrect and the system is much closer to the Sun. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.


Broz M.,Charles University | Mayer P.,Charles University | Pribulla T.,Universitats Sternwarte | Pribulla T.,Slovak Academy of Sciences | And 3 more authors.
Astronomical Journal | Year: 2010

The multiple system V505 Sagittarii is composed of at least three stars: a compact eclipsing pair and a distant component, whose orbit is measured directly using speckle interferometry. In order to explain the observed orbit of the third body in V505 Sagittarii and also other observable quantities, namely the minima timings of the eclipsing binary and three different radial velocities (RVs) detected in the spectrum, we thoroughly test a fourth-body hypothesis - a perturbation by a dim, yet-unobserved object. We use an N-body numerical integrator to simulate future and past orbital evolution of three or four components in this system. We construct a suitable χ2 metric from all available speckle-interferometry, minima-timings, and RV data and we scan a part of a parameter space to get at least some of the possible solutions. In principle, we are able to explain all observable quantities by the presence of a fourth body, but the resulting likelihood of this hypothesis is very low. We also discuss other theoretical explanations of the minima-timing variations. Further observations of the minima timings during the next decade or high-resolution spectroscopic data can significantly constrain the model. © 2010. The American Astronomical Society. All rights reserved.


Zasche P.,Charles University | Uhlar R.,Private Observatory
Astronomy and Astrophysics | Year: 2016

Aims. We present a new updated study of the unique quintuple system of two eclipsing binaries, V994 Her. Methods. Based on new obtained photometric observations, we analysed the period variations of the two eclipsing pairs of V994 Her. Results. We found that the orbital period of the two eclipsing binaries around a common barycenter is about 2.9 yrs instead of the original period, which was reported as 6.3 yrs. Moreover, the system now seems to be close to coplanar (i ∼ 84°), and we also revised the individual masses of all four eclipsing components. The two eclipsing pairs show slow apsidal motion with periods of about 116 and 111 yrs, respectively. Pairs A and B are distant by about 17 mas on the sky, which is encouraging for observers because an interferometric detection may be possible in the next years. Conclusions. All of these results are based on the photometric observations of V994 Her and its detailed analysis of the period changes of the two eclipsing binaries. © ESO, 2016.


Zasche P.,Charles University | Uhlar R.,Private Observatory | Svoboda P.,Private Observatory
Acta Astronomica | Year: 2014

The systems V819 Her, V2388 Oph, and V1031 Ori are triples comprised of an eclipsing binary orbiting with a distant visual component on a longer orbit. A detailed analysis of these interesting systems, combining the two observational techniques: interferometry and apparent period variation, was performed. The interferometric data for these three systems obtained during the last century determine the visual orbits of the distant components in the systems. The combined analysis of the positional measurements together with the analysis of apparent period changes of the eclipsing binary (using the minima timings) can be used to study these systems in a combined approach, resulting in a set of parameters otherwise unobtainable without the radial velocities. The main advantage of the technique presented here is the fact that one needs no spectroscopic monitoring of the visual orbits, which have rather long periods: 5.5 yr for V819 Her, 9.0 yr for V2388 Oph, and 31.3 yr for V1031 Ori, respectively. The eccentricities of the outer orbits are 0.69, 0.33, and 0.92, respectively. Moreover, the use of minima timings of the eclipsing pairs helps us to derive the orientation of the orbit in space with no ambiguity around the celestial plane. And finally, the combined analysis yielded also an independent determination of the distance of V819 Her (68.7±1.8 pc), and V2388 Oph (70.6 ±8.9 pc). We also present a list of similar systems, which would be suitable for a combined analysis like this one.

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