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G. Djurašević P. Rovithis H. Rovithis-Livaniou E. Fragoulopoulou 《Astrophysics and Space Science》2005,296(1-4):311-314
BV light curves of the eclipsing binary UV Leo obtained at the Kryonerion Astronomical Station of the National Observatory of
Athens, Greece, are analyzed. The analysis is based on a Roche configuration with two spots on the secondary surface. The
elements of the two components of the system are calculated and the spot characteristics are given. 相似文献
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A photometric study of a contact binary system, GV Leo is presented. New observations were done using the B VR filter bands. We find that a revised orbital period is 0.26673171 d and the orbital period of this system is decreasing at a rate of dP/ dt = -4.95 × 10-7 d yr-1. The photometric solutions are fairly well fitted at a mass ratio of q = 0.1879, with a fillout factor of f = 17.74%. The results indicate that there exists mass transfer from the more massive component to the less massive one at a rate of relative mass exchange, 6zl/m = -1.09× 10-7 yr-1. It is possible that this weak- contact system, that shows a decreasing orbital period, may undergo contraction of the inner and outer critical Roche lobes and evolve into a deep-contact binary. 相似文献
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Y. Frémat P. Lampens H. Hensberge 《Monthly notices of the Royal Astronomical Society》2005,356(2):545-556
DG Leo is a spectroscopic triple system composed of three stars of late-A spectral type, one of which was suggested to be a δ Scuti star. Seven nights of observations at high spectral and high time-resolution at the Observatoire de Haute-Provence with the ELODIE spectrograph were used to obtain the component spectra by applying a Fourier transform spectral disentangling technique. Comparing these with synthetic spectra, the stellar fundamental parameters (effective temperature, surface gravity, projected rotation velocity and chemical composition) are derived. The inner binary consists of two Am components, at least one of which is not yet rotating synchronously at the orbital period though the orbit is a circular one. The distant third component is confirmed to be a δ Scuti star with normal chemical composition. 相似文献
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D. Manzoori 《Astronomische Nachrichten》2012,333(3):256-265
Solutions of the new standard V‐light curves for the EA type binary UV Leo are obtained using the PHOEBE code (0.31a version). Absolute parameters of the stellar components were then determined, enabling them to be positioned on the absolute magnitude‐color (l.e. MV vs. B – V) isochrones diagram, based on which the age of the system is estimated to be >4×109 yr. Also times of minima data (“O – C curve”) have been analyzed. Apart from an almost sinusoidal variation with a period of 29.63 yr, which modulates the orbital period, and was attributed to a third body orbiting around the system, other cyclic variation in the orbital period and also brightness, with time scales of 24.25 and 22.77 yr were found, respectively. We associate this with a magnetic activity cycle newly reported here for UV Leo (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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In this study, we present the unpublished flare data collected from 222 flares detected in the B band observations of five stars and the results derived by statistical analysis and modeling of these data. Six basic properties have been found with a statistical analysis method applied to all models and analyses for the flares detected in the B band observation of UV Ceti type stars. We have also compared the U and B bands with the analysis results. This comparison allowed us to evaluate the methods used in the analyses. The analyses provided the following results. (1) The flares were separated into two types, fast and slow flares. (2) The mean values of the equivalent durations of the slow and the fast flares differ by a factor of 16.2 ± 3.7. (3) Regardless of the total flare duration, the maximum flare energy can reach a different Plateau level for each star. (4) The Plateau values of EV Lac and EQ Peg are higher than the others. (5) The minimum values of the total flare duration increase toward the later spectral types. This value is called the Half-Life value in models. (6) Both the maximum flare rise times and the total flare duration obtained from the observed flares decrease toward the later spectral types. 相似文献
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D. P. Kjurkchieva D. V. Marchev 《Monthly notices of the Royal Astronomical Society》2007,381(2):663-668
High-resolution spectroscopic observations around the Hα line and BVRI photometry of the eclipsing short-period RS CVn star UV Leo are presented. The simultaneous light-curve solution and radial velocity-curve solution led to the following values of the global parameters of the binary: temperatures T 1 = 6000 ± 100 K and T 2 = 5970 ± 20 K ; masses M 1 = 0.976 ± 0.067 M⊙ and M 2 = 0.931 ± 0.052 M⊙ ; separation a = 3.716 ± 0.048 R⊙ ; orbital inclination ; radii R 1 = 1.115 ± 0.052 R⊙ and R 2 = 1.078 ± 0.051 R⊙ ; equatorial velocities V 1 = 98.8 ± 2.3 km s−1 and V 2 = 89.6 ± 2.7 km s−1 . These results lead to the conclusion that the two components of UV Leo are slightly oversized for their masses and lie within the main-sequence band on the mass–radius diagram, close to the isochrone 9 × 1010 yr. 相似文献