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1.
In this paper a method is proposed for computing the equilibrium structures and various other observable physical parameters
of the primary components of stars in binary systems assuming that the primary is more massive than the secondary and is rotating
differentially about its axis. Kippenhahn and Thomas averaging approach (1970) is used in a manner earlier used by Mohan,
Saxena and Agarwal (1990) to incorporate the rotational and tidal effects in the equations of stellar structure. Explicit
expressions for the distortional terms appearing in the stellar structure equations have been obtained by assuming a general
law of differential rotation of the typeω2 = b
0+b
1
s
2+b
2
s
4, where ω is the angular velocity of rotation of a fluid element in the star at a distance s from the axis of rotation, and b
0, b
1, b
2 are suitably chosen numerical constants. The expressions incorporate the effects of differential rotation and tidal distortions
up to second order terms. The use of the proposed method has been illustrated by applying it to obtain the structures and
observable parameters of certain differentially rotating primary components of the binary stars assuming the primary components
to have polytropic structures.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
In this paper we propose a method for computing the equilibrium structure of differentially rotating polytropic models of the stars. A general law of differential rotation of the type 2=b
0+b
1
s
2+b
2
s
4, which can account for a reasonably large variety of possible differential rotations in the stars has been used. The distortional effects have been incorporated in the structure equations up to second order of smallness in distortion parametersb
0,b
1, andb
2 using Kippenhahn and Thomas' averaging approach in conjunction with Kopal's results on Roche equipotentials in manner similar to the one earlier used by Mohan and Saxena for computing the equilibrium structure of polytropes having solid body rotation. Numerical results have been obtained for various types of differentially rotating polytropic models of stars of polytropic indices 1.5, 3, and 4. Certain differentially rotating models of the Sun which are possible with such a type of law of differential rotation, have also been computed. 相似文献
3.
In the present paper we have considered the problem of determining the equilibrium structure of differentially rotating stars in which the angular velocity of rotation varies both along the axis of rotation and in directions perpendicular to it. For this purpose, a generalized law of differential rotation of the type
2 =b
0+b
1
s
2+b
2
s
4+b
3
z
2+b
4
z
4+b
5
z
2
s
2 (here is a nondimensional measure of the angular velocity of a fluid element distants from the axis of rotation andz from the plane through the centre of the star perpendicular to the axis of rotation, andb's are suitably chosen parameters) has been used. Whereas Kippenhahn and Thomas averaging approach has been used to incorporate the rotational effects in the stellar structure equations, Kopal's results on Roche equipotentials have been used to obtain the explicit form of the stellar structure equations, which incorporate the rotational effects up to second order of smallness in the distortion parameters. The method has been used to compute the equilibrium structure of certain differentially rotating polytropes. Certain differentially rotating polytropes. Certain differentially rotating models of the Sun have also been computed by using this approach. 相似文献
4.
L. V. Glazunova 《Astronomy Letters》2011,37(6):414-419
Based on two high-dispersion spectra of the close binary BW Boo, we have detected lines of the secondary component whose contribution
to the combined spectrum does not exceed 2%. We have determined the rotation velocities of the components and spectroscopic
orbital elements. Numerous lines of neutral and ionized iron have been used to determine the effective temperature and surface
gravity for the primary component. The photometric light curves for this binary have been solved for the first time. Its primary
component is an A2Vm star with a mass of 2 ± 0.1M
⊙ and a radius of 1.9 ± 0.4R
⊙. Its rotation velocity is 2 km s−1, which is a factor of 18 lower than the pseudo-synchronous velocity for this component. The G6 secondary component, a T Tau
star, has a rotation velocity of 17 km s−1, amass of 1.1M
⊙, and a radius of 1 R
⊙. The age of the binary has been estimated to be 107 yr. 相似文献
5.
In the present paper we have studied the eigenfrequencies of small adiabatic barotropic pseudo-radial and nonradial modes of oscillations of the white dwarf models of rotating stars in binary systems. In this work the methodology of Mohan and Saxena (in Astrophys. Space Sci. 113:155, 1985) has been used that utilizes the averaging technique of Kippenhahn and Thomas (in Proc. IAU Colloq., vol. 4, p. 20, 1970) and certain results on Roche equipotential as that given by Kopal (in Advances in Astronomy and Astrophysics, Academic Press, 1972). The objective of this study is to investigate the effects of rotation and/or tidal distortion on the periods of oscillations of rotationally and/or tidally distorted white dwarf models of stars assuming it to be the primary component of the binary system and rotating uniformly. The results of present study show that the eigenfrequencies (both radial and nonradial modes) of the rotationally distorted and rotationally and tidally distorted white dwarf model of stars in binary systems tend to decrease under the influence of rotational distortions and rotational and tidal distortions, respectively. However, results are contrary for tidally distorted white dwarf model of stars. 相似文献
6.
In this paper we present a method for computint the equilibrium structures of rotationally distorted stars as well as rotationally and tidally distorted primary components of the stars in binary systems. The method is based on the averaging technique of Kippenhahn and Thomas (1970) and utilizes the concepts of Roche equipotentials (Kopal, 1972). The method takes into account terms up to second-order of smallness in the rotational and tidal distortion parameters. The use of the method in obtaining the equilibrium structures of certain rotationally and (or) tidally distorted models of Main-Sequence stars is also illustrated. 相似文献
7.
The mass loss to be expected from the corona of a rotating F2-star is calculated. The rotation is supposed to be rigid up to a certain distances, as if it were maintained by a strong magnetic field. Dependent on the values of the rotational velocity the mass loss can increase to 26–40% forv
rot up to 200 km s–1. 相似文献
8.
An estimate for the anisotropy of the turbulent viscositys is given in a convective layer heated from below and rotating around a vertical axis. In the case of two-dimensional convection,
there is a stationary regime withs⊇2 regardless of the rotation. In the case of three-dimensional convection in a slowly rotating layer (with the Taylor number
equal to 1600), nonstationary turbulent regimes take place withs⊇1.6 forR=2.5×104 (R is the Rayleigh number) ands⊇1.2 forR=104.
The parameters plays an, important role in the theory of differential rotation of the convective solar or stellar envelopes. So far, it
has been evaluated empirically or semi-empirically. Some prospects in the development of the theory of differential rotation
are discussed here in terms of the moment theory of hydrodynamic fields. The relation between this strict approach and an
anisotropic viscosity approximation is considered. 相似文献
9.
Analysis of the available observational data for the α-Persei cluster members shows that rotation effects on the intermediate-band
indices c1 and (u-b) are considerable. In c1, rotation produces a reddening of 0.040 magnitudes per 100 km s-1 In (u-b) the effect for B stars is found to be 0.06 magnitudes per 100 km s-1 ofV sin i.
The binaries and peculiar stars are found to behave differently in the colour excess (due to rotation) versusV sin i diagrams. These empirical effects can be utilised to recalibrate these colour indices and also to separate members
that are either chemically peculiar or in binary systems. 相似文献
10.
The models of non-rotating and rotating 2.31M
\ stars of Population I composition have been calculated, starting at the threshold of stability. A 2.31M
\ star was chosen to compare the results with the observational parameters of the primary component of the well-known detached binary YZ Cassiopeiae. The effects of rotation on the internal structure during the evolution of the star were studied by constructing sequences of axisymmetric rotating models under the assumption that angular momentum was conserved according to a predetermined angular velocity distribution depending on the structure of the star.The first section of this paper deals with effects of rotation on the evolutionary behaviours of the 2.31M
\ star through the pre-Main-Sequence evolution as well as the zero-age Main Sequence.In the second section of this paper, the evolutionary studies have been extended up to near-hydrogen exhaustion phase in order to obtain a theoretical model corresponding to the given mass and radius of the primary component of YZ Cassiopeiae. The theoretical models were found to be in a good agreement with observational parameters. The computed rotating models of the primary of YZ Cassiopeiae indicates that its evolutionary age is 6.01×108 years; and the central hydrogen content 0.183 — which means that about 75% of its original value was depleted. 相似文献
11.
Jacques Laskar 《Celestial Mechanics and Dynamical Astronomy》2005,91(3-4):351-356
Recently, Breiter et al. [Celest. Mech. Dyn. Astron., 2004, 88, 153–161] reported the computation of Hansen coefficients X
k
γ ,m
for non-integer values of γ. In fact, the Hansen coefficients are closely related to the Laplace b
s
(m), and generalized Laplace coefficients b
s,r
(m) [Laskar and Robutel, 1995, Celest. Mech. Dyn. Astron., 62, 193–217] that do not require s,r to be integers. In particular, the coefficients X
0
γ ,m
have very simple expressions in terms of the usual Laplace coefficients b
γ +2
(m), and all their properties derive easily from the known properties of the Laplace coefficients. 相似文献
12.
J.L. Dunlap 《Icarus》1976,28(1):69-78
Ten lightcurves and UBV photometry of 433 Eros were obtained between August 1972 and May 1975. The absolute magnitude of the lightcurve maximum is 10.75 and the phase coefficient is 0.025 mag/deg. There may be a small difference in B-V color between the northern and southern hemispheres. The pole of the axis of rotation is directed toward λ0 = 16°, β0 = 12°, ecliptic longitude and latitude, respectively, and the rotation is direct with a sidereal period of 0.d219599 or 5h16m13s4 ± 0.s2. The dimensions derived from the polarimetric albedo and the lightcurve amplitudes are 12km × 12km × 31km for a smooth cylinder with hemispherical ends. 相似文献
13.
The superfine structure of the active region in Orion KL has been investigated in the H2O maser line at two epochs, December 23, 1998, and April 24, 1999, with an angular resolution as high as 0.01 mas. A bright central source, a bipolar outflow ejector with two nozzles spaced 0.008 mas apart, has been identified. The impact of the ejected flows causes precession of the rotation axis and gives rise to a jet structure in the shape of diverging helixes of opposite signs. The longitudinal velocities of the flows differ by 0.12 km s?1. The flow emission at the exit from the nozzles is linearly polarized and oriented at an angle of 22° relative to the rotation axis or parallel to the flow velocities. Their brightness temperature exceeds T b > 1018 K. The width of the emission line profiles is 0.43 km s?1, their relative shift is ±0.06 km s?1, and the orientations of the polarization planes differ by 45°, which determines the extraordinary rotation of the polarization plane, 25°/km s?1. 相似文献
14.
In this paper a method is proposed for computing the eigenfrequencies of small adiabatic barotropic modes of oscillations of rotationally and tidally-distorted stars. The method utilizes Kippenhahn and Thomas approach and concepts of Roche equipotentials to incorporate up to second-order the effects of rotation and tidal distortion terms on the eigenfrequencies. The proposed method has also been used to compute the eigenfrequencies of certain barotropic modes of oscillation of some rotationally and tidally distorted models of 10M
, and 2.5M
Main-Sequence stars. 相似文献
15.
M. Blaha 《Solar physics》1971,17(1):99-116
Equilibrium population of Fexiv levels in coronal conditions was calculated including configurations 3s
23p, 3s3p
2, 3s
23d, 3p
3, 3s3p3d, 3s
24s, 3s
24p, 3s
24d, 3s
24f. Relative populations of selected levels are given in Table VII. Figure 1 shows the dependence of relative intensities of
the strongest lines on electron density. Certain line ratios can be used for the determination of N
e
.E.g., at T=2 × 106
K and with a dilution factor 0.4, the intensity ratio of λ211.3 and λ219.0 changes by a factor of 65 if N
e
increases from 107 to 1011 (Table VIII). Cascades from the 3s3p3d and 3p
3 configurations are important in the population of some levels of 3s3p
2 (Table VI). A possibility of identification of additional lines in the solar spectrum is indicated.
NAS-NRC Resident Research Associate. 相似文献
16.
Tu-Hwan Kim 《Astrophysics and Space Science》1980,68(2):355-384
TheUBV photoelectric light curve of IW Per as an ellipsoidal variable was obtained and a number of spectrograms were taken with dispersion of 10 Å mm–1. New spectroscopic orbital elements are determined for this single-line spectroscopic binary to beK
1=99.3 km s–1, =0.2 km s–1,a sini=1.80R
andf(m)=0.093m
. From analysis of the light curve, the geometric ellipticity coefficient of the distorted components is determined to beZ=0.037.Applying the second-order theory of light variation due to distorted components (Kopal and Kitamura, 1968), the orbital inclination and fractional radius of the primary component can be deduced simultaneously to bei=63° andr
1=0.294. By takingm
1=2.0m
for the mass of the primary component with spectral type A5Vm, the mass of the secondary can be also deduced to bem
2=1.08m
, which would correspond to a G0-type if it is a Main-Sequence star. These elements indicate that the system is a non-eclipsing detached close binary.From intensity measurements of the lines Caii-K, Srii 4215 and Scii 4320 on twenty-eight good spectrograms taken at various phases, those intensities and the intensity ratio Sc/Sr are found to vary systematically with phase. From these variations the distribution of the local metallicity on the surface of the Am primary component is discussed in connection with the distribution of the local surface temperature. 相似文献
17.
M. Srinivasa Rao 《Monthly notices of the Royal Astronomical Society》2005,357(3):983-993
A general expression for the gravity darkening of the tidally and non-uniformly rotating Roche components of close binary systems is used to calculate the uniform rotational effects on line profiles in an expanding atmosphere. We consider a non-local thermodynamic equilibrium (non-LTE) two-level atom approximation in an extended atmosphere, and use Von Zeipel's theorem for the incident radiation at the maximum optical depth (τ=τmax ) in the atmosphere. These calculations are performed with uniform rotational velocities of 1, 4 and 8 mtu (mean thermal units). It is found that rotation dilutes the radiation field which is similar to the expansion velocity.
We also study rotational aspects, which make the outer layers of the star distorted. The equation of line transfer is solved in the comoving frame of the expanding atmosphere of the primary using complete redistribution in the line. We use a linear law for the velocity of expansion such that the density varies as r−3 , where r is the radius of the star, satisfying the law of conservation of mass. It is found that rotation broadens the line profile, and P-Cygni-type line profiles are obtained. 相似文献
We also study rotational aspects, which make the outer layers of the star distorted. The equation of line transfer is solved in the comoving frame of the expanding atmosphere of the primary using complete redistribution in the line. We use a linear law for the velocity of expansion such that the density varies as r
18.
V. V. Bobylev 《Astronomy Letters》2006,32(12):816-826
We have redetermined the kinematic parameters of the Gould Belt using currently available data on the motion of nearby young (log t < 7.91) open clusters, OB associations, and moving stellar groups. Our modeling shows that the residual velocities reach their maximum values of ?4 km s?1 for rotation (in the direction of Galactic rotation) and +4 km s?1 for expansion at a distance from the kinematic center of ≈300 pc. We have taken the following parameters of the Gould Belt center: R 0 = 150 pc and l 0 = 128°. The whole structure is shown to move relative to the local standard of rest at a velocity of 10.7 ± 0.7 km s?1 in the direction l = 274° ± 4° and b = ?1° ± 3°. Using the derived rotation velocity, we have estimated the virial mass of the Gould Belt to be 1.5 × 106 M ⊙. 相似文献
19.
We have studied a sample containing ~6000 OB stars with proper motions and trigonometric parallaxes from the Gaia DR2 catalogue. The following parameters of the angular velocity of Galactic rotation have been found: Ω0 = 29.70 ± 0.11 km s-1 kpc-1, Ω'0 = -4.035 ± 0.031 km s-1 kpc-2, and Ω 0 = 0.620 ± 0.014 km s-1 kpc-3. The circular rotation velocity of the solar neighborhood around the Galactic center is V0 = 238 ± 5 km s-1 for the adopted Galactocentric distance of the Sun R0 = 8.0 ± 0.15 kpc. The amplitudes of the tangential and radial velocity perturbations produced by the spiral density wave are fθ = 4.4 ± 1.4 kms-1 and fR = 5.1 ± 1.2 kms-1, respectively; the perturbation wavelengths are λθ = 1.9 ± 0.5 kpc and λR = 2.1 ± 0.5 kpc for the adopted four-armed spiral pattern. The Sun's phase in the spiral density wave is χ⊙ = -178° ± 12°.
相似文献20.
We present the results of our infrared observations of WR 140 (=V1687 Cyg) in 2001–2010. Analysis of the observations has
shown that the J brightness at maximum increased near the periastron by about 0
m
.3; the M brightness increased by ∼2
m
in less than 50 days. The minimum J brightness and the minimum L and M brightnesses were observed 550–600 and 1300–1400 days after the maximum, respectively. The JHKLM brightness minimum was observed in the range of orbital phases 0.7–0.9. The parameters of the primary O5 component of the
binary have been estimated to be the following: R(O5) ≈ 24.7R
⊙, L(O5) ≈ 8 × 105
L
⊙, and M
bol(O5) ≈ −10
m
. At the infrared brightness minimum, T
g ∼ 820–880 K, R
g ≈ 2.6 × 105
R
⊙, the optical depth of the shell at 3.5 μm is ∼5.3 × 10−6, and its mass is ≈1.4 × 10−8
M
⊙. At the maximum, the corresponding parameters are ∼1300 K, 8.6 × 104
R
⊙, ∼2 × 10−4, and ∼6 × 10−8
M
⊙; the mean rate of dust inflow (condensation) into the dust structure is ∼3.3 × 10−8
M
⊙ yr−1. The mean escape velocity of the shell from the heating source is ∼103 km s−1 and the mean dispersal rate of the shell is ∼1.1 × 10−8
M
⊙ yr−1. 相似文献