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1.
Quantities characterizing light curves of contact binaries of W UMa-type are introduced. For 2700 cases, theoretical light curves of contact binaries are computed by the light curve synthesis method, and characteristic quantities for these light curves are tabulated. An example of application of the table to the light curve analysis of contact binaries is shown, and the errors inherent in the solution are also discussed.  相似文献   

2.
The solution of light curves of eclipsing binaries provides the simplest way of measuring the basic physical parameters of stars. The development of computers and numerical methods enables us to perform an analysis of large amount of photometric data by comparing it to more and more sophisticated physical models which are also suitable for stellar systems with different peculiarities. Nevertheless, some parameters of stellar systems are poorly determined by light curves alone, and simultaneous fitting together with other data is preferable. The progress of instrumentation not only improves the precision and resolution of data, but also overcomes the classical gaps between stellar systems observable as visual, photometric and spectroscopic binaries. This opens new problems in the development of techniques of data analysis, which can be treated as a generalization of light curve modeling. Some of these directions are outlined here. In particular, the disentangling of spectra with line-profile variability due to proximity effects is discussed.  相似文献   

3.
Light curves have been calculated for the model of a binary system consisting of two spherical components, imbedded in a common spherically-symmetric, isotropically-scattering envelope with radially-varying opacity. The periodically-varying screening of stellar radiation by the envelope gives rise to regular light changes, which are similar to stellar eclipses during a superior conjunction of the components and in maxima resemble the light changes due to the reflection effect for Algol-type binaries, whereas for systems with nearly equal luminosities of the components they match light variations, caused by the gravitational distortions of stellar figures.It is shown that the light changes in AO Cas can be interpreted in terms of our model and we propose to call binaries of that type gas-eclipsed variables. The observed light curves RY Gem, RS CVn, VW Cep are compared with the model curves. It is indicated that the light curve of the Algol-type system RY Gem can be interpreted in the framework of the adopted model, provided that stellar eclipses are accompanied by the screening effect of the envelope.Asymmetry, local fluctuations, different widths of minima, and some other peculiarities of the observed light curves are discussed within the context of our model. It can be regarded as a certain optical counterpart of the Roche model, since the isophotes of the envelope resemble the Roche equipotentials in their behaviour.  相似文献   

4.
The space experiment CoRoT will provide continuous monitoring and high accuracy light curves of about sixty thousand stars. Selected binary systems will be observed in the Additional Program frame as targets of long and continuous pointed observations. Moreover, thousands of new binaries will certainly be detected and hundreds of them will have extremely accurate light curves. This will allow studies of fine effects on the light curves, monitoring of stellar activity and, in combination with ground-based observations, will provide exquisite determination of stellar parameters. Among the new discoveries of interesting systems of special value will be those of low mass binaries.  相似文献   

5.
We present photometric analysis of 8 short-period eclipsing binaries discovered and observed at Astronomical Observatory at Kolonica Saddle between 2007 and 2010 with different instruments. We determined their orbital periods and performed photometric analysis of their light curves. We found that 3 systems are detached binaries, 4 systems are over-contact binaries of W UMa type and one system is semi-detached with the secondary component filling its Roche lobe. Light curves of 2 systems exhibit asymmetries, explained by spot(s) on the surface of the components.  相似文献   

6.
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.  相似文献   

7.
We present a new catalogue of variable stars compiled from the data taken for the University of New South Wales Extrasolar Planet Search. From 2004 October to 2007 May, 25 target fields were each observed for one to four months, resulting in ∼87 000 high-precision light curves with 1600–4400 data points. We have extracted a total of 850 variable light curves, 659 of which do not have a counterpart in the General Catalogue of Variable Stars, the New Suspected Variables catalogue or the All Sky Automated Survey southern variable star catalogue. The catalogue is detailed here, and includes 142 Algol-type eclipsing binaries, 23 β Lyrae-type eclipsing binaries, 218 contact eclipsing binaries, 53 RR Lyrae stars, 26 Cepheid stars, 13 rotationally variable active stars, 153 uncategorized pulsating stars with periods <10 d, including δ Scuti stars, and 222 long period variables with variability on time-scales of >10 d. As a general application of variable stars discovered by extrasolar planet transit search projects, we discuss several astrophysical problems which could benefit from carefully selected samples of bright variables. These include (i) the quest for contact binaries with the smallest mass ratio, which could be used to test theories of binary mergers; (ii) detached eclipsing binaries with pre-main-sequence components, which are important test objects for calibrating stellar evolutionary models and (iii) RR Lyrae-type pulsating stars exhibiting the Blazhko effect, which is one of the last great mysteries of pulsating star research.  相似文献   

8.
Synthesis methods for light and radial velocity curves allow one to find the physical parameters of the components of binary systems of different types. We describe the basics of a new light curve synthesis algorithm for binaries that contain stars with extended expanding atmospheres. The algorithm can be used to study, e.g., light curves of binaries that contain Wolf-Rayet stars.  相似文献   

9.
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.  相似文献   

10.
This paper is devoted to the effects of dark starspots on observed light curves and line profiles. A new formulation of the starspot model with multiple spots and arbitrary spot shapes is derived which allows for a numerical solution of light and colour curves and distorted line profiles simultaneously. The effects of differential rotation and the existence of a penumbra have also been considered. A parameter study demonstrates the influences of different spot parameters on the theoretical light curves and rotation profiles. The computer code is applicable for single stars as well as for eclipsing close binaries allowing for ellipticity effect and reflection effect.  相似文献   

11.
In a previous paper, we have presented photometric studies of four recently discovered contact binaries (Djurašević, et al., 2016; hereafter Paper I) that were observed by the 1.88 m telescope of the Kottamia Astronomical Observatory (KAO) in Egypt. In this paper we continue studying two more recently discovered, by some of us, contact binaries UCAC4 479-113658 and UCAC4 479-113711, and analyze their light curves to determine orbital and physical parameters using the modeling program of G. Djurašević as in Paper I. The analysis shows that the two systems are W UMa contact binaries of late type main-sequence stars with a bright spot on the secondary less massive cool star of the first system; and spot on each component of the later system. We also conclude that both systems are most likely to be of the A-type class.  相似文献   

12.
Since about ten years coordinated programs of photoelectric observations of asteroids are carried out to derive rotation rates and light curves. Quite a number of those asteroids exhibit features in their light curves, with similar characteristics as variable stars and especially eclipsing binaries. This would allow also an interpretation that there might be an evidence for the binary nature of some asteroids, based on observational hints. A few examples are given and a list of indications for the possible binary nature of asteroids, based on their light curve features, is presented.Paper presented at the Lembang-Bamberg IAU Colloquium No. 80 on Double Stars: Physical Properties and Generic Relations, held at Bandung, Indonesia, 3–7 June, 1983.  相似文献   

13.
We have developed a stellar wind model for OB supergiants to investigate the effects of accretion from a clumpy wind on the luminosity and variability properties of high-mass X-ray binaries. Assuming that the clumps are confined by ram pressure of the ambient gas and exploring different distributions for their mass and radii, we computed the expected X-ray light curves in the framework of the Bondi–Hoyle accretion theory, modified to take into account the presence of clumps. The resulting variability properties are found to depend not only on the assumed orbital parameters but also on the wind characteristics. We have then applied this model to reproduce the X-ray light curves of three representative high-mass X-ray binaries: two persistent supergiant systems (Vela X−1 and 4U 1700−377) and the supergiant fast X-ray transient IGR J11215−5952. The model can reproduce the observed light curves well, but requiring in all cases an overall mass loss from the supergiant about a factor of 3–10 smaller than the values inferred from ultraviolet lines studies that assume a homogeneous wind.  相似文献   

14.
All methods existing today for computation of the elements of eclipsing binaries require photometric observations to cover the complete revolution of binaries, outside as well as within the eclipses. The maximum light and the depth of the eclipses are to be determined prior to any analysis, and the light curves are to be expressed in terms of the total light at quadratures. A method has been introduced in the present paper to enable us to obtain the elements of eclipsing binaries by an analysis of, not the whole, but a part of their eclipse light curves. In the new method no empirical knowledge of the maximum light or depth of eclipes is needed, and no normalization is necessary. The method can be used in any models (ellipsoidal, Roche, etc.). However, the larger the phase coverage of the light changes considered for the computation of the elements, the better the determinacy (or smaller the errors) is obtained.  相似文献   

15.
A lot of data in time domain were obtained by the Kepler mission, including many contact binaries. Long-term observation lets us obtain more information about the short time scale variation in their light curves or in their orbital periods. Unfortunately, the exposure time is too long (most of them are 30 minutes). Hence, many variations in light curves are smoothed. To avoid this problem, we analyzed some Kepler contact systems with both long-cadence mode and short-cadence mode data. Using the latest version of the Wilson-Devinney code, we obtained the physical parameters of a batch of contact binaries and find out four targets(KIC 5123176, KIC 5296877, KIC 8496820, KIC 9776718) have low mass ratios (q  <  0.25) and one target (KIC 7950962) has a mass ratio very close to unit.  相似文献   

16.
An unusual timing and spectral state of a black hole microquasar XTE J1550-564 observed with RXTE is analyzed. Millisecond variabilities are found, which are significantly shorter than the minimum possible time scale in the light curves of black hole binaries, as suggested by Sunyaev & Revnivtsev (2000). The X-ray spectral fitting result indicates that there is an unusual soft component in the spectrum, which may be responsible for the millisecond variabilities. The millisecond variabilities as well as the unusual soft spectral component should be produced from some small, but independent active regions in the accretion disk.  相似文献   

17.
Four eclipsing binaries, which show apparent changes of period, have been studied with respect to a possible presence of the light–time effect. With a least squares method we calculated new light elements of these systems, the mass function of the predicted third body, and its minimum mass. We discuss the probability of the presence of such bodies in terms of mass function, changes in radial velocity and third light in solution of light curves.  相似文献   

18.
The EW-type eclipsing binaries are strongly interacting systems known to have often both component stars filling their crucial Roche lobes and having a common envelope. We present new BVRI light curves of the eclipsing binaries ZTF J214226.88+435,827.1 (ZTF21+43) and KAO-EGYPT J214216.38+440,015.1 (KAO21+44) based on CCD observations acquired with the 1.88-m Kottamia Astronomical Observatory (KAO) at Newtonian and Cassegrain telescope focus. The modeling results show that these two systems are to be W UMa contact binaries belonging to EW subtypes. All the light curves show the inverse O'Connell effect. We computed new ephemeris for each system using our times of minima and that available in the literature. Using our new times of minima and epochs for both systems from all available observations, the orbital period changes of these structures are studied for our systems. Using the PHOEBE package, a preliminary determination of the two systems' photometric orbital and physical parameters has been present. The positions of the systems were also depicted on the Hertzsprung-Russell (H-R), M-L, and Teff-L diagrams to test their evolutionary status.  相似文献   

19.
CO Lacertae is one of the very few known binaries with both a short period of apsidal motion and good M, L, R data. Our newU, B, V light curves provide two times of minima and a check on Semeniuk's value forP aps. This is the first published example of an eclipsing binary analysed in terms of a physical model (as opposed to a model based on spherical or ellipsoidal star figures) which allows for eccentric orbit effects. The light curves show some peculiarities — particularly a large, probably intrinsic, scatter.  相似文献   

20.
Photometric observations are presented in V and I bands of six eclipsing binaries at the lower limit of the orbital periods for W UMa stars. Three of them are newly discovered eclipsing systems. The light curve solutions reveal that all shortperiod targets are contact or overcontact binaries and six new binaries are added to the family of short-period systems with estimated parameters. Four binaries have components that are equal in size and a mass ratio near 1. The phase variability shown by the V-I colors of all targets may be explained by lower temperatures on their back surfaces than those on their side surfaces. Five systems exhibit the O'Connell effect that can be modeled by cool spots on the side surfaces of their primary components.The light curves of V1067 Her in 2011 and 2012 are fitted by diametrically opposite spots. Applying the criteria for subdivision of W UMa stars to our targets leads to ambiguous results.  相似文献   

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