Light and colour curve observations and analysis of the short period eclipsing binary system UV Psc

In the present work we have presented and analysedB andV light curves and the (B-V)-colour curve of the short period (RS CVn type) binary system UV Psc, and derived absolute information from the available data.x ² minimization procedures were utilized to a large extent in fitting light and colour curves.The solutions show the binary to be at a distance of about 90 pc with two detached components which are close to the main sequence (G2 and K0). The inclination of the orbit is close to 90°Photometric irregularities present in the light curve are briefly considered in relation to current ideas on RS CVn systems, and the colour information indicates a locally hotter (rather than cooler) region is responsible for the irregularities.     

Brightness oscillations in models of young binary systems with low-mass secondary components

We consider a model for the cyclic brightness variations of a young star with a low-mass companion that accretes matter from the remnants of a protostellar cloud. At small inclinations of the binary orbit to the line of sight, the streams of matter and the density waves excited in the circumbinary disk can screen the primary component of the binary from the observer. To study these phenomena, we have computed grids of hydrodynamic models for binary systems by the SPH method based on which we have calculated the phase light curves for the different orientations of the orbit. The model parameters were varied within the following ranges: the component mass ratio q = 0.01–0.1 and the eccentricity e = 0–0.5. We adopted optical grain characteristics typical of circumstellar dust. Our computations have shown that the brightness oscillations with orbital phase can have a complex structure. The amplitudes and shapes of the light curves depend strongly on the inclination of the binary orbit and its orientation relative to the observer and on the accretion rate. The results of our computations are used to analyze the cyclic activity of UX Ori stars.     

A photometric study of a new short period eclipsing sdB binary NSVS 07826147

NSVS?07826147 and NSVS?04818255 were suspected as possible eclipsing sdB binary systems by Kelley and Shaw. In order to investigate the short period eclipsing sdB binaries, we have listed them as our observing targets and began to monitor it from March 2009. Till now, we have obtained four complete CCD light curves and 16 high precise times of light minimum of NSVS?07826147. All light curves show strong reflection and a very narrow eclipse, which implies that NSVS?07826147 should be a new short period eclipsing sdB binary. For the system NSVS?04818255, no eclipse character was found in the light curves according to our observations. However, we found that a star near NSVS?04818255 is a close binary system with a period of about 0.32498 days. Up to now, only seven short period eclipsing sdB binary systems have been found, including NSVS?07826147. With the new precise epochs obtained by us, the new period of this system is derived as 0.16177046(5) days, which can be used to predict the epochs of light minimum. Furthermore, the light curves of NSVS?07826147 are analyzed using the Wilson–Van Hamme code and the testing photometric solutions are presented and discussed.     

Light curve variations of the eclipsing binary V367 Cygni

The long-period eclipsing binary star V367 Cygni has been observed photoelectrically in two colours,B andV, in 1984, 1985, and 1986. These new light curves of the system have been discussed and compared for the light-variability with the earlier ones presented by Heiser (1962). Using some of the previously published photoelectric light curves and the present ones, several primary minima times have been derived to calculate the light elements. Any attempt to obtain a photometric solution of the binary is so complicated by the peculiar nature of the light curve caused by the presence of the circumstellar matter in the system. Despite this difficulty, however, some approaches are being carried out to solve the light curves which will be discussed shortly.     

A New Magnetically Active Binary System Discovered in Yunnan-Hong Kong Wide Field Survey

We present a newly discovered magnetically active binary system detected by Yunnan-Hong Kong wide field survey, with an orbital period of 0.60286 days. Two color photometry for the system was performed using the 1 m Cassegrain telescope of Yunnan Observatories with its CCD (Charge-Coupled Device) camera. In the observed light curves, there are clearly different light maxima existed in the out-of-eclipse regions. We made spectroscopic observations for the binary system using the 2.4 m telescope and YFOSC (Yunnan Faint Object Spectrograph and Camera) of Lijiang station of Yunnan Observatories, China. The radial velocity curve was derived for primary star of the binary system. The primary star exhibited strong chromospheric activity, which confirms that the distortion of the light curves results from the starspot activity on the primary star. Through analyzing the light curves and RV (Radial Velocity) curve mentioned above by means of the W-D (Wilson-Devinney) code, orbital parameters and starspot configuration of the binary system are obtained. Finally, we have discussed the properties of the binary system, and given the prospects on the future work.     

RV Piscium: a marginal contact binary system

The first complete charge-coupled device (CCD) light curves in B and V bands of the short-period binary system, RV Psc, are presented. It is found that the light curves of RV Psc are symmetric and belong to the EW type rather than the EA type as described in the 4th edition of the GCVS. Photometric solutions were derived by using the 2003 version of the Wilson–Devinney (W-D) method. It is shown that RV Psc is a marginal contact system (f=5.8%±6.6%) with a mass ratio of q=0.5978±0.0096. The temperature difference between both components is only 17 K. Analysis of the O-C curve suggests that the period of RV Psc shows a long-term continuous decrease at a rate of dP/dt=?5.89×10^?8 days/year. The long-time period decrease, the marginal-contact configuration, and the astrophysical parameters of the binary system, all suggest that it is a newly formed marginal contact binary from a case A mass transfer and will evolve into a normal overcontact binary.     

Ultraviolet photometry from the orbiting astronomical observatory XXII. Ultraviolet light variation ofβ Lyrae

Six-color ultraviolet light curves of the complex eclipsing binary system Lyr were obtained with the OAO-2 Wisconsin Experiment Package. The filters had a typical width at half maximum of 150 to 200 Å and centered at 1430, 1550, 1910, 2460, 2980 and 3320 Å. The most striking characteristics of the ultraviolet light curves are that the secondary minimum deepens at shorter wavelengths. This indicates that we arenot observing the eclipse effect of two stars having roughly a Planckian distribution of energy. In combination with the high resolution far ultraviolet spectra of Lyr recently obtained withCopernicus (OAO-3) Princeton Telescope Spectrometer, it is concluded that the far ultraviolet light curves are dominated by emission from the high temperature gas surrounding the binary system. The ultraviolet observations with OAO-2 andCopernicus are consistent with a model in which the enigmatic secondary component involves a gravitationally collapsed object, i.e., a black hole; however, alternative models are also admissible.     

Further evidence for the binary nature of HR 3084

New photometric and spectroscopic observations yield further evidence for the binary nature of the early-type star HR 3084. Shape and small amplitude of the visual and IR light curves indicate that the light variations are essentially due to ellipsoidal effects rather than to Cep variability.Based on observations collected at the European Southern Observatory, La Silla, Chile.     

Photometric analysis of recently discovered eclipsing binary GSC 00008-00901

Photometric analysis of BVR _C light curves of newly discovered eclipsing binary GSC 0008-00901 is presented. The orbital period is improved to 0.28948(11) days. Photometric parameters are determined as well. The analysis yielded to conclusion that system is an over-contact binary of W UMa type with components not in thermal contact. The light curves from 2005 show the presence of a spot on the surface of one of the components, while light curves from 2006 are not affected by maculation.     

Effects of gravitational microlensing of binary and multiple stars

The observation of microlensing events towards the Large Magellanic Cloud and Galactic Bulge discovers a new population of our Galaxy which is that of dark bodies with masses of the order of 0.1M . Astronomy has now a unique ability: one can use the microlensing as a space telescope with extremely high angular resolution. Here we discuss the opportunity of the application of this ability to observation of close binaries. Stars in a binary system move around their barycenter and as a result the apparent motion is modulated by binary motion. The light curve of this microlensing event becomes nonsymmetrical. If a binary has two stars with different spectral types, one can expect significant variation of color during microlensing effect. Accurate light curves for some typical binaries have been calculated and are presented here. The total fraction of binaries in our Galaxy is around 50%. Therefore one can expect half of the microlensing events to have nonsymmetrical and wavelength depending light curves which would indicate that background star is binary. Our opinion is that the absence of these light curves are due to some selection effect. This leads to an underestimation of the density of the dark body population in our Galaxy by a factor of about two.     

New photoelectric observations of VW Cephei

The aim of the present paper is to present the newB andV light curves of the eclipsing binary VW Cep, obtained with the 48-in. reflector of the National Observatory of Athens, Greece.In the introduction general information for the system is given. In Section 2 some observational and reductional details are given and the obtained light curves are represented. Section 3 deals with the period of the system which was found to continue its shortening. Finally, in Section 4, a general discussion concerning our light curves is given.     

Some specific features of light curves of (39) Laetitia, (87) Sylvia, (90) Antiopa,and 2006 VV2 asteroids

The results of photometric observations of (87) Sylvia, 2006 VV2, (90) Antiopa, and (39) Laetitia asteroids in 2006–2008 are presented. The specific features of light curves are considered for each object. In particular, for asteroid (87) Sylvia, possible mutual phenomena in this triple system are identified. Asteroid 2006 VV2 manifests a strong dependence of the light curve on the filter color, which testifies to the presence of inhomogeneities on its surface. The previously unknown brightness variation period with a duration of about three days was obtained for this asteroid. For binary asteroid (90) Antiopa, the strong dependence of its brightness on the phase angle was noticed; this may testify to the very flattened shape of its components. Considerable time variations of the shape of the light curve for asteroid (39) Laetitia may testify either to its complex shape or to its binary character.     

云南-香港宽视场巡天新发现的一个磁活动双星系统

云南-香港宽视场巡天新发现了一个磁活动双星系统,其轨道周期为0.60286 d.利用云南天文台1 m光学望远镜附加CCD (Charge-Coupled Device)相机,观测得到了这个双星系统的V、Rc双色光变曲线,结果表明该系统食外存在明显的测光畸变.借助云南天文台丽江2.4 m望远镜附加云南暗弱天体光谱成像仪(Yunnan Faint Object Spectrograph and Camera, YFOSC)对该双星系统的分光观测,测定了该双星系统主星的视向速度曲线并发现该系统的主星表面存在着强烈的色球活动,从而证明系统的光变曲线畸变源自主星的黑子活动.使用W-D (Wilson-Devinney)程序分析上述观测得到的光变曲线和视向速度曲线,得到了该双星系统的轨道参数以及黑子参数.最后,对该系统的特性进行了讨论并对未来的工作进行了展望.     

A photometric study of the contact binary AZ Virginis

New light curves and photometric solutions of the contact binary AZ Vir are presented in this paper. The light curves appear to exhibit a typical O'Connell effect, with Maximum I being 0.021 mag (V) and 0.023 mag (B) brighter than Maximum II, respectively. From the observations, six times of minimum light were determined and from the present times of minimum light and those collected from the references, the light elements of the system were improved. The light curves were analyzed by means of the Wilson‐Devinney program. The results suggest that AZ Vir is a W‐subtype contact binary with a mass ratio of q = 0.623(2). The asymmetry of the light curves is explained by star spot models. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Theory of the light curves of eclipsing systems with oscillating components: I

The aim of the present investigation will be to develop a theory of the light changes of the eclipsing systems in which one (or both) components oscillate(s) freely-radially or non-radially-in period(s) which may (though need not) be synchronized with that of their orbit. The light curves exhibited by systems with oscillating components will, in general, beasymmetric; and these oscillations may, in fact, be the cause of asymmetries observed in many eclipsing systems with evolved components (for which such oscillations-far from being anomalous-should be the rule rather than exception). The present paper will be concerned with an investigation of photometric phenomena arising from oscillations of theeclipsing components of close binary systems-cutting off (partly or wholly) the star (spherical or distorted) which undergoes eclipse.In Section 2, which follows a brief introductory survey aiming to place the entire subject in its historical perspective, a theory will be given of the light curves of close binary systems, in the frequency-domain, which are affected byradial oscillations of the eclipsed or eclipsing star; while Sections 3 and 4 will be devoted to a similar treatment ofnon-radial oscillation of the secondary (eclipsing) component distorted by equilibrium tides, or axial rotation with constant angular velocity. As will be shown, a frequency-domain approach will enable us to describe all these phenomena in algebraic terms; with auxiliary results required to this end relegated to three Appendices to the main text (in order not to render the latter too discursive and impede the main line of the argument).A similar treatment of photometric phenomena which may arise in such systems from oscillations of their components which undergo eclipse is being postponed for a subsequent communication.     

B and V photometry and analysis of the eclipsing binary RZ Cas

Photoelectric light curves of the eclipsing binary RZ Cas are presented forB andV filters. The light curves are analysed for light and geometrical elements, starting with a previously suggested preliminary method. The approximate results thus obtained are then optimised through the Wilson-Devinney computer programs.     

γ-rays from binary system with energetic pulsar and Be star with aspherical wind: PSR B1259−63/SS2883

At least one massive binary system containing an energetic pulsar, PSR B1259−63/SS2883, has been recently detected in the TeV γ-rays by the HESS telescopes. These γ-rays are likely produced by particles accelerated in the vicinity of the pulsar and/or at the pulsar wind shock, in comptonization of soft radiation from the massive star. However, the process of γ-ray production in such systems can be quite complicated due to the anisotropy of the radiation field, complex structure of the pulsar wind termination shock and possible absorption of produced γ-rays which might initiate leptonic cascades. In this paper, we consider in detail all these effects. We calculate the γ-ray light curves and spectra for different geometries of the binary system PSR B1259−63/SS2883 and compare them with the TeV γ-ray observations. We conclude that the leptonic inverse-Compton model, which takes into account the complex structure of the pulsar wind shock due to the aspherical wind of the massive star, can explain the details of the observed γ-ray light curve.     

Three-colours photoelectric observations of W UMA-system BB Pegasi

The paper givesUBV photoelectric light curves of the eclipsing binary BB Peg obtained in one of the nights in August 1982 and four nights of November 1984. A comparison has been made with previous light curves of this binary system. Two salient points arise from the light curves, (i) the depth of the primary eclipse could be variable, (ii) the period of the system has probably been increased.     

Estimation of Light Time Effects for Close Binaries in Triple Systems

We discuss implementation of light time effects in a general binary star program that solves for third body orbit parameters and binary star parameters together. The program combines radial velocities and light curves within a coherent analysis and can use data that are very unevenly distributed over time. By analyzing whole curves, the program has access to more information than only from eclipse timings. Results for λ Tau and VV Ori are shown.     

Evidence for pole switching in the magnetic cataclysmic variable BY Camelopardalis

An analysis of X-ray and optical light curves of the magnetic cataclysmic variable (MCV) BY Cam is presented. This system is one of three MCVs in which the spin period of the white dwarf and the binary orbital period differ by ∼1 per cent. As such these 'BY Cam' stars are important objects with which to probe the field structure of the magnetic white dwarf and ultimately the nature of synchronization of AM Her binaries. We confirm asynchronous rotation of the magnetic white dwarf with respect to the binary. We find evidence that the accretion stream accretes directly on to the white dwarf as in AM Her systems, but further, the stream impacts on to different magnetic poles over the course of the beat period. We present evidence that the optical and hard X-ray light curves modulate in phase, but together they are out of phase with the soft X-ray light curve. We confirm the spin down of the white dwarf which is expected to lead to the synchronization of the spin and orbital periods of BY Cam.