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1.
In this paper we present the observations of the eclipsing binary LX Per, which were obtained in 1983. There is a wave-like distortion at outside eclipses with an amplitude ranging from 0.03 to 0.08 mag. The wave-like distortion was removed with a new approach. Then, the light curves were analyzed by the methods of Wood and Nelson, Davis, and Etzel. The absolute parameters of the components were also calculated. The physical parameters of the components indicate that the cooler star has seperated or has been departing from the Main Sequence. 相似文献
2.
The influence of a bubble-like structure around a starburst within the H II regions on the shape of the ionizing spectrum and the generation of the observed emission lines was studied using multicomponent photoionization modeling. The distributions of density and other physical parameters in such bubble-like structures were determined by Weaver et al. in 1977. The first two components represent the region of the stellar wind from the central starburst region. The gas density and electron temperature distributions in these components were described by the solution of the system of equations of continuity and energy transfer with account for the heat conductivity. The third component represents a thin layer of gas with a high density that emerges due to the passage of a normal shock wave of the stellar wind. The fourth component represents a “typical” H II region. The ionizing radiation spectra were set from the calculated evolutionary models whose free parameters determine the physical conditions within the “bubble.” The influence of the stellar wind bubble on the shape of the ionizing radiation spectrum and the generation of fluxes in important emission lines was analyzed. 相似文献
3.
The method for the multicomponent photoionization modeling of the H II region radiation surrounding the starburst knot is presented. The internal structure of the H II region has been determined using the evolutionary model of the superwind bubble from the starburst center. Models of Chevalier and Clegg (1985) and Weaver et al. (1977) have been used to determine the radial distribution of the gas density, the velocity of gas layers, and the temperature in the region of the superwind free expansion and in the cavity, respectively. The chemical content of the internal components of the bubble has been set by the results of the modeling of the evolutionary population synthesis. External components of our models describe a high-density, thin layer of gas formed by the shock wave of stellar superwind from the surrounding gas and a typical H II region, respectively. Input model parameters have been taken from the precalculated evolutionary starburst models based on three types of evolutionary tracks. Evolutionary grids of multicomponent low-metallicity models are calculated. A comparative analysis of the results of their calculation with the observational data has been carried out. 相似文献
4.
We consider a method of reconstructing the structure delay of extended radio sources without constructing their radio images. The residuals derived after the adjustment of geodetic VLBI observations are used for this purpose. We show that the simplest model of a radio source consisting of two point components can be represented by four parameters (the angular separation of the components, the mutual orientation relative to the poleward direction, the flux-density ratio, and the spectral index difference) that are determined for each baseline of a multi-baseline VLBI network. The efficiency of this approach is demonstrated by estimating the coordinates of the radio source 0014+813 observed during the two-week CONT14 program organized by the International VLBI Service (IVS) in May 2014. Large systematic deviations have been detected in the residuals of the observations for the radio source 0014+813. The averaged characteristics of the radio structure of 0014+813 at a frequency of 8.4 GHz can be calculated from these deviations. Our modeling using four parameters has confirmed that the source consists of two components at an angular separation of ~0.5 mas in the north–south direction. Using the structure delay when adjusting the CONT14 observations leads to a correction of the average declination estimate for the radio source 0014+813 by 0.070 mas. 相似文献
5.
A. Caproni H. Monteiro Z. Abraham 《Monthly notices of the Royal Astronomical Society》2009,399(3):1415-1428
Evidence of jet precession in many galactic and extragalactic sources has been reported in the literature. Much of this evidence is based on studies of the kinematics of the jet knots, which depends on the correct identification of the components to determine their respective proper motions and position angles on the plane of the sky. Identification problems related to fitting procedures, as well as observations poorly sampled in time, may influence the follow-up of the components in time, which consequently might contribute to a misinterpretation of the data. In order to deal with these limitations, we introduce a very powerful statistical tool to analyse jet precession: the cross-entropy method for continuous multi-extremal optimization. Only based on the raw data of the jet components (right ascension and declination offsets from the core), the cross-entropy method searches for the precession model parameters that better represent the data. In this work we present a large number of tests to validate this technique, using synthetic precessing jets built from a given set of precession parameters. With the aim of recovering these parameters, we applied the cross-entropy method to our precession model, varying exhaustively the quantities associated with the method. Our results have shown that even in the most challenging tests, the cross-entropy method was able to find the correct parameters within a 1 per cent level. Even for a non-precessing jet, our optimization method could point out successfully the lack of precession. 相似文献
6.
M. M. Zakirov 《Kinematics and Physics of Celestial Bodies》2008,24(1):25-35
We made up a list of eclipsing variables from The Sixth Catalog of Orbits of Visual Binary Stars and supplemented it with physical parameters and some orbital elements of triple stars. A histogram of the angles between the orbital planes of close and wide pairs was built. These angles were shown to be no greater than 20° in two-thirds of cases, and the difference between the angles was shown to increase with semimajor axis of visual orbit. The distribution of the ratios between long and short periods has local maxima in certain intervals. The dynamical sum of the masses of triple-system components turned out to be in good agreement with the sum of the masses of close binary components estimated by precise methods and the mass of the tertiary component determined from the mass-luminosity relation. Most of tertiary components were found to have masses half as large as the sums of the masses of close pair components. Our estimates suggest that the precession periods of the orbits of close binary systems range from several thousand to several tens of million years. 相似文献
7.
Three-color photoelectric UBV light curves of the close binary system V448 Cyg obtained at the Abastumani Astrophysical Observatory are analyzed using a new code by Djurasevi. A new value for the ratio of the masses of the components, which is the fundamental parameter for determining the absolute elements of the system, has recently been published. The parameters obtained in our analysis differ substantially from those published previously because the new mass ratio has been employed. The location of the components of V448 Cyg on a mass-logg plot shows that this system, similarly to XZ Cep and V382 Cyg, is in a phase subsequent to a rapid transfer of mass.Translated from Astrofizika, Vol. 48, No. 1, pp. 59–68 (February 2005). 相似文献
8.
CCD light curves of the Algol type eclipsing binaries DP Cep, AL Gem, FG Gem, UU Leo, CF Tau and AW Vul were analysed using the Wilson–Devinney code and new geometric and absolute parameters were derived. Due to cyclic apparent orbital period changes of the systems, probably caused by the Light-Time Effect, the contribution of a third light was taken into account in the light curve solution. All the reliable timings of minima found in the literature were used to study the period variations and search for the presence of a tertiary component in the systems. A comparison between the parameters of the third body derived from the light curve and orbital period analyses is also discussed. Moreover, the absolute parameters of the eclipsing binary components were also used to determine their current evolutionary state. 相似文献
9.
Zdenek Mikulá 《中国天文和天体物理学报》2010,10(6)
Seven charge-coupled device(CCD)photometric times of light minimum of the overcontact binary BS Cas which were obtained from 2007 August to November and one CCD light curve in the R band which was observed on 2007 September 24 and October 15,are presented.It is found that the light curve of BS Cas has characteristics like a typical EW-type light variation.The light curve obtained by us is symmetric and shows total eclipses,which is very useful for determining photometric parameters with high precision.Photometric solutions were derived by using the 2003 version of the Wilson-Devinney code.It shows that BS Cas is a W-subtype overcontact binary(f = 27.5% ± 0.4%)with a mass ratio of q = 2.7188 ± 0.0040.The temperature difference between the two components is 190 K.Analysis of the O-C curve suggests that the period of AE Phe shows a long-term continuous decrease at a rate of dP/dt=-2.45 × 10-7 dyr-1.The long-time period decrease can be explained by mass transfer from the primary to the secondary. 相似文献
10.
A method for determining the velocity field parameters free from the distortions due to the systematic variations of stellar parallaxes over the celestial sphere is proposed. The method is based on the approximation of parallaxes as a function of coordinates on the sphere using spherical harmonics and can be applied in those cases where the solar motion cannot be eliminated from the stellar proper motions. Numerical experiments have shown that our method is able to obtain accurate coordinates of the solar apex and to calculate the kinematic parameters of the Ogorodnikov-Milne model to within three coefficients of the decomposition of parallaxes into first-order spherical harmonics. Examples of applying the method to the stellar proper motions of the Hipparcos catalogue, which admits checking the results using trigonometric parallaxes, are provided. Such a check has been found to yield a positive result only for nearby stars at heliocentric distances that do not exceed 400 pc and for which the parallaxes were determined with a relative error of at least 30%. An interesting feature of this method is the possibility to construct the shape of the figure which is formed by the deviations of the parallaxes from the sphere corresponding to the average parallaxes of the stars under consideration. It should be specially emphasized that all of this is done in the complete absence of information about the stellar parallaxes. The “solar terms” of the stellar proper motions that are formed by the products of the parallaxes by the solar motion components relative to the centroid of stars are the main source of information about the parallaxes here. 相似文献
11.
The dark energy model with barotropic equation of state, which interacts with dark matter by gravitation and by other force, which causes the energy-momentum exchange between them, is considered. Both components are described in approximation of ideal fluid, which are parameterized by density, equation of state and effective sound speed parameters. The three types of interactions between dark components are considered: interaction independent from their densities, interaction proportional to energy density of dark energy, and interaction proportional to energy density of dark matter. The equations that describe the expansion dynamics of homogeneous and isotropic Universe and evolution of densities of both components for different values of interaction parameter are obtained on the bases of the general covariant conservation equations and Einstein’s ones. For three kinds of interactions, the existing of the range of values of parameters of dark energy for which the densities of dark components are negative was shown. The conditions of positivity of energy density of dark energy and dark matter were written for which the constraints on the value of parameter of interaction were derived. The dynamics of expansion of the Universe with these interactions of dark energy and dark matter is analyzed. 相似文献
12.
13.
利用12万组大气阻力资料，对DTM－1994模式进行改造，获得了一个新的大气模式，该模式的特点是：1．利用2阶周日峰效应，代替了原来模式中的复杂的周日效应表达式，减少了模式参数（少于50个），并使模式参数均具有明确的物理意义，2．分清了模式的主要参数和次要参数，在主要参数中，又分清了利用了阻力资料可以改进的参数和可能改不好的参数．3．与MSIS－1990和DTM－1994模式相比，其互差可以被接受，说明使用卫星阻力资料可以进行大气模式动态改正，不仅能测定大气总密度，并且能测定大气的分密度，4．与卫星轨道相比较，改进有显优于MSIS－1990模式，在120km轨道附近，改进模式密度比MSIS－1990模式大10％，同时我们在卫星陨落期预报中发现，MSIS－1990模式密度比实际大气密度小9％，这说明改进模式的密度与实际大气的密度基本接近。 相似文献
14.
W. A. Rahoma F. A. Abd El-Salam M. K. Ahmed 《Journal of Astrophysics and Astronomy》2009,30(3-4):187-205
The present work is concerned with the two-body problem with varying mass in case of isotropic mass loss from both components of the binary systems. The law of mass variation used gives rise to a perturbed Keplerian problem depending on two small parameters. The problem is treated analytically in the Hamiltonian frame-work and the equations of motion are integrated using the Lie series developed and applied, separately by Delva (1984) and Hanslmeier (1984). A second order theory of the two bodies eject mass is constructed, returning the terms of the rate of change of mass up to second order in the small parameters of the problem. 相似文献
15.
New CCD light curves of the recently detected eclipsing variable GSC 4589‐2999 were obtained and analysed using the Wilson‐Deninney code. Spectroscopic observations of the system allowed the spectral classification of the components and the determination of their radial velocities. The physical properties and absolute parameters of the components and an updated ephemeris of the system are given (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
16.
Using multicomponent photoionization simulation, we investigated the impact of bubble-like structures around starbursts inside the low-metallicity H II regions on the ionization spectrum shape and emission line forming. Radial distribution of density values and other physical parameters of bubble-like structures were taken from Weaver et al. (Weaver et al., 1977, p. 377). The first and second inner components of such models describe the free expansion zone of superwind from the central starburst region and rarefied hot gas of the cavern thermalized by inverse shock wave, respectively. The gas density and electron temperature distributions into these components are obtained from the solution of the system of equations of continuity and energy transfer, including heat conductivity. The third component is a thin shell of high density gas formed from the gas surrounding a bubble and made by direct shock wind wave. The gas density in this component was obtained from isobaric condition at contact discontinuity between the second and third components. Input spectra of the ionizing radiation were obtained from the starburst evolutional models. The evolution grid of the multicomponent low-metallicity photoionization models with free parameters determining physical conditions inside the bubble-like structure was calculated. The impact of bubble-like structure on the change of ionization spectrum shape and the formation of fluxes of important emission lines in low-metallicity case was analyzed in detail. 相似文献
17.
The effect of rotation and a general magnetic field on the luminosity, radius, and effective temperature of the upper Main-Sequence stars has been investigated using a perturbation analysis. The magnetic field profile prevailing inside the star is assumed to have both poloidal and toroidal components. The case of constant as well as differential rotation is admitted. Model calculations indicate that these stellar parameters modify considerably as a result of coupling between rotation and the magnetic field. 相似文献
18.
D. Manzoori 《Astronomische Nachrichten》2016,337(6):652-661
New standardized V ‐band light curves (LCs) for the eclipsing binary SV Cam have been modeled using the PHOEBE program (v. 0.31a). Absolute parameters of the stellar components were then determined, enabling them to be positioned on the mass‐radius diagram. Analysis of eclipse minima timing data (O – C diagrams) indicated two cyclic periods of 48.0 and 23.3 yr. These cyclic variations of the orbital period are interpreted in terms of motion of a third body around the system and magnetic activity cycle modulating the orbital period of SV Cam via the Applegate (1992) mechanism. The use of the Applegate model for SV Cam has been checked by examining the long term brightness variation and calculating some important parameters of this system. The results of these calculations favor the modulation of the orbital period by the Applegate mechanism. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
19.
《New Astronomy》2016
Stellar rotation depends on different parameters such as age, mass, initial chemical composition, initial angular momentum, and environment characteristics. The range of values of these parameters causes the dispersion in the rotation period distributions observed in young stellar clusters/associations. We focus our investigation on the effects of different circumstellar environments on stellar rotation. More specifically, we consider the effects of a perturber stellar companion on the accretion-disc lifetime at early evolution stages.We are searching in stellar Associations for visual triple systems where all stellar parameters are similar, with the only exceptions of the unknown initial rotation period, and of the circum-stellar environment, in the sense that one of the two about equal-mass components has a close-by third ‘perturber’ component.In the present study we analyze the 35-Myr old visual triple system TYC 9300-0891-1AB + TYC 9300-0529-1 in the young Octans stellar association consisting of three equal-mass K0V components. We collected from the literature all information that allowed us to infer that the three components are actually physically bound forming a triple system and are members of the Octans Association. We collected broad-band photometric timeseries in two observation seasons. We discovered that all the components are variable, magnetically active, and from periodogram analysis we found the unresolved components TYC 9300-0891-1AB to have a rotation period P = 1.383 d and TYC9300-0529-1 a rotation period P = 1.634 d.TYC 9300-0891-1A, TYC 9300-0891-1B, and TYC 9300-0529-1 have same masses, ages, and initial chemical compositions. The relatively small 16% rotation period difference measured by us indicates that all components had similar initial rotation periods and disc lifetimes, and the separation of 157 AU between the component A and the ‘perturber’ component B (or vice-versa) has been sufficiently large to prevent any significant perturbation/shortening of the accretion-disc lifetime. 相似文献
20.
针对当前利用大地水准面模型求解垂线偏差精度不高、稳健性差的问题,设计了一种严密的垂线偏差抗差最小二乘解法.首先,基于大地水准面与垂线偏差的关系,采用EGM2008 (Earth Gravity Model 2008)重力场模型计算参数初始解;然后,引入中位数抗差法,并选用Huber权函数计算等价权,迭代计算出稳健的垂线偏差最小二乘解;最后,结合两个实测算例对设计方法进行验证.试验结果表明,该方法计算的垂线偏差分量与约定真值最大偏差在0.5′′左右,相较于对比方法精度更高;同时,该方法能有效抵抗粗差值的影响,具有较强的稳健性. 相似文献