Analysis of Extra-Solar Planetary Transits Using Tools from Eclipsing Binaries

Analytical formulae for the computation of the photometric elements of extra-solar planetary transits are presented. They were initially derived for the study of well-detached eclipsing binaries and are valid for any degree of limb darkening and type of transit as well as for eccentric orbits. The only assumption is that the projections of the star and the planet on the plane of the sky are well represented by circular discs. The procedure to get valid ranges for the involved parameters, as well as to make precise estimations of initial parameters, using the analytical nature of the equations is given together with some discussion on their practical application. Examples are shown for OGLE-TR-113, representative of a light curve obtained with ground-based telescopes, and HD 209458 with a precise light curve obtained with the Hubble Space Telescope.     

EROS-II Variable Stars: Eclipsing Binaries in the EROS Microlensing Surveys

More than 10 years of microlensing survey observations by the EROS Collaboration have monitored several million stars, amongst them several thousand eclipsing binary stars. In this poster we present some of the difficulties and rewards of the study of this immense database.Based on observations made at ESO by the EROS collaboration     

The accelerated Kepler problem

The accelerated Kepler problem (AKP) is obtained by adding a constant acceleration to the classical two-body Kepler problem. This setting models the dynamics of a jet-sustaining accretion disk and its content of forming planets as the disk loses linear momentum through the asymmetric jet-counterjet system it powers. The dynamics of the accelerated Kepler problem is analyzed using physical as well as parabolic coordinates. The latter naturally separate the problem’s Hamiltonian into two unidimensional Hamiltonians. In particular, we identify the origin of the secular resonance in the AKP and determine analytically the radius of stability boundary of initially circular orbits that are of particular interest to the problem of radial migration in binary systems as well as to the truncation of accretion disks through stellar jet acceleration.     

The Eclipsing Binary bx Andromedae and its Orbital Period Behaviour

The orbital period variations of the eclipsing binary BX And are examined analysing its (O–C) diagram 1) with the standard method, in which the minima times are fitted by the quadratic ephemeris combined with an assumed light-time effect, and 2) with the first continuous method. The results from the use of the two methods are, as was expected, different.     

Light-Time Effect in the Eclipsing Binaries GO Cyg, GW Cep, AR Aur and V505 Sgr

Orbital period changes of the eclipsing binaries GO Cyg and GW Cep are explained by the light-time effect for the first time. New minima of the eclipsing binary AR Aur improve the predicted light-time orbit. The light-time orbit with the quadratic ephemeris of the binary matches the new observations of V505 Sgr better than the linear one. As the light-time effect fits in corresponding O − C diagrams of all four systems have been reaching extreme values, the observations of minima times in forthcoming years are highly desirable.     

Influence of Interstellar and Atmospheric Extinction on Light Curves of Eclipsing Binaries

Interstellar and atmospheric extinctions redden the observational photometric data and they should be handled rigorously. This paper simulates the effect of reddening for the modest case of two main sequence T ₁ = 6500 K and T ₂ = 5500 K components of a detached eclipsing binary system. It is shown that simply subtracting a constant from measured magnitudes (the approach often used in the field of eclipsing binaries) to account for reddening should be avoided. Simplified treatment of the reddening introduces systematics that reaches ∼0.01 mag for the simulated case, but can be as high as ∼0.2 mag for, e.g., B8 V-K4 III systems. With rigorous treatment, it is possible to uniquely determine the colour excess value E(B−V) from multi-colour photometric light curves of eclipsing binaries.     

A Library of Eclipsing Binary Light-Curves: Fast Initial Parameters Estimation, and on the Uniqueness of the Inverse Problem

In order to improve the light curve solutions we suggest to use a new approach. A library of the Fourier-coefficients (up to 20th term) of (several millions of) light curves was constructed each of the light curves has different input parameters. A light curve solution is made in a very fast way: its discrete Fourier-transform yields not more than some simple number which are compared to the Fourier-coefficients in the library. A chi-squared test can help us to estimate very good initial parameters for the differential correction analysis. The library can also be used to study the uniqeness problem of the light curve solutions. Here we investigated the uniqueness of the spot solution of SV Cam.     

Ccd Photometry of Neglected Eclipsing Binaries – Kz Dra, Lr Cam and Im Vul

We present ephemerides and solutions of one Algol-type (KZ Dra) and two overcontact systems (LR Cam and IM Vul) based on V(RI)_C CCD observations obtained in the project Prosper (network of amateur observers).     

The WASP Project and SuperWASP Camera

The WASP project and infrastructure supporting the SuperWASP Facility are described. As the instrument, reduction pipeline and archive system are now fully operative we expect the system to have a major impact in the discovery of bright exo-planet candidates as well in more general variable star projects.     

The W UMa-type Stars Program: First Results, Current Status and Perspectives

We present the results of a statistical investigation of the period-color and period-bolometric magnitude relations using a carefully selected sample of 120 contact systems with known physical parameters.     

Extra-solar planets: Detection methods and results

Since 1995, more than 200 extra-solar planets have been discovered, demonstrating not only that planetary systems are common, but also that planets may come in a large variety of flavors. As the number of detections grows, statistical studies of the properties of exoplanets and their host stars can be conducted to unravel some of the key physical and chemical processes leading to the formation of planetary systems. In this paper we describe the major techniques used to search for extra-solar planets. In particular, we discuss in more detail the radial-velocity and the transit techniques, responsible for the discovery of the bulk of the known planets orbiting solar-type stars. We then present the main results from the planet surveys, describing the global properties of the newfound worlds.     

激变双星的角动量损失机制和演化

本文详细研究了激变双星系统的演化，发现磁制动机制导致的角动量损失要求星风的量级为１０￣（－１１）－１０￣（－１２）Ｍ＿⊙ｙｒ￣－１，这比太阳风强１０￣２－１０￣３倍，表明磁星风机制失效，作者认为驱动双星系统演化的角动量损失是由来自致密星的吸积盘外边缘物质溢出的惯性离心力所致。     

The Rise of New Planets: Super-Earths and Sub-Neptunes

With the ceaseless progress of detecting technology, over 3500 exo-planets have been discovered. It is interesting but unexpected that the majority of the detected exoplanets are unlike any planets in our solar system. They have a size and mass between the Earth and the Neptune, and thus they are called as Super-Earths or Sub-Neptunes. In this article, I introduce these newly rising planets and review our current knowledge of their physical properties, orbital properties, and origins. Finally, I discuss the promising and exciting prospects.     

The First Photometric Analyses Of Four New Discovered Ew-Type Eclipsing Binaries: GSC 1848-1264, GSC 0804-0118, GSC 0619-0232 And GSC 2936-0478

Photometric solutions of four new discovered W UMa-type binaries were carried out for the first time by using the 2003 version of the W-D program. It is discovered that all of the four systems are over-contact binaries. Two binaries, GSC 0804-0118 and GSC 2936-0478, are of A-subtype, while two other binaries, GSC 1848-1264 and GSC 0619-0232, are of W-subtype. From our solutions, the fundamental orbital and physical parameters were determined. For GSC 0619-0232 and GSC 2936-0478, the asymmetries of the light curves (i.e., the O'Connell effect) were explained by the presence of dark spots on the more massive components. Our photometric results reveal that GSC 0619-0232 is an important and interesting system. It is a W-type over-contact binary with a low mass ratio of q = 0.100 and a high over-contact degree of f = 93.4%, which suggests that GSC 0619-0232 may be evolved into a single rapid-rotating star.     

The First Photometric Analysis of Two Low Mass Ratio Totally Eclipsing Contact Binaries:TIC 393943031 and TIC 89428764

Photometric analysis of the contact binaries TIC 393943031 and TIC 89428764 was carried out using Transiting Exoplanet Survey Satellite and SuperWASP data for t...     

Bm Cas: A Long-Period Eclipsing Binary with A Supergiant and a Common Envelope

New results of UBVR photometry of the long-period eclipsing binary BM Cas obtained at Tallinn Observatory between 1979 and 1996 are discussed.     

Modelling The Irradiated Upper Atmospheres Of Unevolved Companions In Precataclysmic Binaries (Pcb): Evidences On Thermal Instability

We report on our results of modelling the physical processes in the uppermost layers of strongly irradiated atmospheres of low mass unevolved companions in Precataclysmic Binaries (PCBs). Reprocessing of Lyman continuum L _c radiation from the hot subdwarf (sdw) primary is studied in detail. We solve explicitly a set of equations of hydrostatic, ionization and thermal equilibrium to calculate the intensity of the reprocessed emergent radiation in recombinations for an optically thin plasma. We consider contributions from free-free and bound-free transitions. Diffuse radiation is taken into account, but the effects of self-absorption of the re-emitted radiation are neglected. For a purely hydrogenic atmosphere and typical values of incident fluxes, densities, gas pressures for the irradiated upper atmospheric layers, we find that the L _c radiation will be absorbed and re-emitted in recombinations within a column of effective thickness (10⁶–10⁸) cm of HII, depending on the electron density, the effective temperature of the sdw and the separation between the components. One of the non-trivial results of our model computations lies in the overheating of the uppermost layers of the irradiated atmosphere: the equilibrium temperature of the gas turns out to be considerably higher than the blackbody temperature following from the diluted incoming radiation of sdw. Energy balance considerations reveal that roughly 25–50% of the L _c flux is expended on the ionization of H and is re-emitted subsequently in recombinations. The remaining portion of the L _c flux is spent on readjustment of the uppermost layers of the irradiated atmosphere. One of the consequences is the onset of thermal instability in these layers.     

Rr CrB and Algol – The First and Last Star in Zdeněk Kopal’s Life with Binaries

Several important turning points appeared in the personal life and scientific career of Zdeněk Kopal, every time, when he entered a new field of research. Four particular periods of his life will be commented in the present paper: the studies in Prague and early observations in the variable star programme of the Czech Astronomical Society; the first lectures on close binaries at Harvard; the intermezzo of lunar research; and the last period after 1989, when Zdeněk Kopal returned several times to Prague University.     

Analysis of optical and IR light curves of the WR binary V444 Cygni: are clumps still present?

The results of analysis of new broad band U, J, K, photometric observations of WN5+O6 binary V444 Cyg are presented. Comparison to the old optical data of Cherepashchuk et al. (1984) and IR data of Hartmann (1978) shows that the optical light curve is stable over more than 10 years, while the new infrared light curves are significantly different from the Hartmann's ones. The difference between old and new infrared light curves poses a problem for clumpy structure of WR wind proposed by Cherepashchuk et al. as well as for standard smooth flow wind theory.