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1.
Estimates of the pulsation massesM Q and of massesM g=gR2/G (g is the surface gravity;R, the mean stellar radius; andG, the gravitational constant) of 89 Delta Scuti-variables have been obtained. An intercomparison of three kinds of masses —M e, Mg, andM Q — is performed; the evolutionary massesM e of the same variables were estimated in a previous paper (Tsvetkov, 1986). It is pointed out that within the limits of the accuracy of determination, the three kinds of masses agree for the majority of the stars under study. For several varaibles, however, there is a considerable discrepancy between the estimates of the pulsation massesM Q and the estimates of the massesM e andM g. Arguments are represented, which may alleviate or even remove this mass discrepancy for some of these stars. It is shown that the results from the comparison between the three kinds of masses of the considered Delta Scuti-stars are not very sensitive to the choice of the system of evolutionary tracks and the adopted chemical composition as well as to the evolutionary phases of the variables (core or shell hydrogen burning). The variations of the chemical composition in most of the stars under study are probably not very large.  相似文献   

2.
Double-lined spectra have been obtained at 2 Å/mm for the Mn star 112 Herculis AB. The components are shown to be a B6.5V star and A2V star. Hydrogen-line-blanketed models are used to calculate atmospheric abundances. The best models appear to beT e=13500 K, logg=4.0, T =2.5 km/sec for the primary; andT e=10000K, logg=4.2, T =6 km/sec for the secondary. Both stars appear to have the same abundances. Helium, carbon, magnesium, aluminum, silicon, calcium, vanadium, and nickel appear to be considerably underabundant; phosphorus, scandium, titanium, manganese, iron, gallium, and mercury considerably overabundant; and chromium, strontium, and zirconium normal in abundance.  相似文献   

3.
Two hyades giant stars, and Tau, have been studied from an analysis of strong line profiles. We get for Tau,T e =4750K and logg=2.7, and for Tau,T e =4700K and logg=2.8. Hydrogen-to-metal ratio for the two stars is nearly the same as that of solar value.  相似文献   

4.
Photospheric models were calculated for 90 stars with effective temperatures between 2500 K and 41600 K for five logg-values ranging from 1 to 5. Molecule formation was taken into account. In order to have an idea about possible instabilities in the different stellar layers some quantities, characteristic for convection and turbulence were calculated, such as the Rayleigh-, Reynolds-, Prandtl- and Péclet-numbers. It turned out that all the investigated stars contain unstable layers, including the hottest. Nevertheless, only stars with effective temperatures of 8300 K or less contain layers where the convective energy transport is important. For all stars the convective velocities were calculated and also the generated mechanical fluxes in the convection zones were tabulated.Under the hypothesis that this mechanical energy flux is responsible for the heating of the corona, coronal models were constructed for the Sun and for some stars with effective temperatures between 5000 K and 8320 K for logg-values of 4 or 5.For Main Sequence stars the largest fluxes are generated in F-stars; stars withT eff=7130 K and logg=4 possess also the hottest and most dense coronas with a computed temperature of 3.7·106 K and logN e =10.5.The solar corona computed in this way, on the basis of a photospheric mechanical flux of 0.14·108 erg cm–2 sec–1, has a temperature of 1.3·106 K and logN e =9.8. This density is apparently too high, but even when including in the computations all theoretical refinements proposed in the last few years by various authors it does not appear possible to obtain a solar coronal model with a smaller density.However, when taking into account the inhomogeneous structure of the chromosphere and by associating the calculated mechanical fluxes to the coarse mottles, and lower fluxes to the undisturbed regions we find a mean coronal temperature of 1.1·106 K and a mean logN e -values of 9. The computed velocity of the solar wind at a distance of 104 km above the photosphere has a value between 7 and 11 km sec–1. These latter values are in fair agreement with the observations.  相似文献   

5.
The algorithm for determining effective optical thickness of absorption line formation in a plane-parallel homogeneous planetary atmosphere is presented. The case of anisotropic scattering is considered. The results of numerical calculations of τ e (μ0) at the scattering angle γ = π for some values of the single scattering albedo λ and the parameter of the Heyney-Greenstein scattering indicatrix g are given. The refined equation for the function T m (−μ, μ0) is presented.  相似文献   

6.
Calculations of the acoustic energy generation for helium-rich composition show that the maximum acoustic energy generation is located around 12000 K at logg=4 and 15000 K at logg=6. The author's suggestion in his last paper that a helium star Sgr may have a corona seems to be justified. X-ray from a corona around a helium star is strongest when the physical parameters of the star are logg6 andT e15000 K. But the total energy flux is too small to account for the observed X-ray sources.Presented at the Trieste Colloquium on Mass Loss from Stars, September 12–16, 1968.  相似文献   

7.
Physical parameters and radial pulsation modes are determined for three Delta Scuti stars in the Praesepe cluster: HD 73345, HD 73712, and HD 73746. Their agest and evolutionary massesM eare interpolated in the track systems of Iben (1967) and Paczyski (1970). By combining these age estimates with our previous results for nine other Delta Scuti-stars in the Praesepe cluster (Tsvetkov, 1989), the following weighted mean age estimates of this cluster are obtained: (14.2 ± 1.3) × 108 yr (Iben) and (5.4 ± 0.4) × 108 yr (Paczyski). Age and evolutionary mass estimates of the twelve cluster variables are also obtained in the modern track system of Maeder and Meynet (1988), in which the weighted mean cluster age is (15.3 ± 1.0) × 108 yr.Pulsation massesM Qcalculated from the fitting formulae of Faulkner (1977) and Fitch (1981) as well as massesM g=gR 2 / G were evaluated for the twelve cluster variables by Tsvetkov (1990) or in the present paper. In most cases there is a satisfactory agreement between our estimates of massesM e,M g, andM Q.Due to a large disagreement between the long period and low luminosity of the star HD 73746, its radial pulsation mode and pulsation massM Qcannot be evaluated.  相似文献   

8.
We present NeV/MgV and SiVII/MgVII theoretical line intensity ratios as a function of electron densityN e and temperatureT e . These are shown in the form of ratio-ratio diagrams, which should in principle allow bothN e andT e to be deduced for the emitting region of the solar plasma. We apply these diagnostics in the solar atmosphere, and discuss the available observations made from space. In most cases, however, we deduceN e andT e from the computed absolute line intensities in a spherically symmetric model atmosphere of the Sun. Possible future applications of this investigation to spectral data from the Coronal Diagnostic Spectrometer (CDS) on the Solar and Heliospheric Observatory (SOHO) are briefly discussed.  相似文献   

9.
Expansions of the functions (r/a)cos jv and (r/a)m sin jv of the elliptic motion are extended to highly eccentric orbits, 0.6627 ... <e<1. The new expansions are developed in powers of (e–e*), wheree* is a fixed value of the eccentricity. The coefficients of these expansions are expressed in terms of the derivatives of Hansen's coefficients with respect to the eccentricity. The new expansions are convergent for values of the eccentricity such that |e–e*|<(e*), where the radius of convergence (e*) is the same of the extended solution of Kepler's equation. The new expansions are intrinsically related to Lagrange's series.  相似文献   

10.
Foster  V. J.  Keenan  F. P.  Reid  R. H. G.  Doyle  J. G.  Zhang  H. L.  Pradhan  A. K.  Widing  K. G. 《Solar physics》1997,170(2):217-225
Recent calculations of Mgviii electron and proton impact excitations rates are used to derive theoretical electron temperature (T e)- and density (N e)-sensitive emission line ratios involving transitions in the 315–782 Å wavelength range. Some of these ratios are presented in the form of ratio–ratio diagrams, which should in principle allow both N e and T e to be deduced. These results are compared with solar observational data from Skylab, but agreement between theory and observation is very poor, probably due to blending.  相似文献   

11.
In this paper the ionization stage and the relationship connecting electronic pressure, gaseous pressure and temperature are studied in a H-deficient, extreme-He mixture which, also, has an overabundance of C (HdC mixture). For comparison purposes a similar analysis is made for a solar mixture and for a metal-deficient one. In our study we take account of the formation of negative ions and of molecules; the selected physical conditions roughly suit those in stellar atmospheres. The relation log (P g /P e) vs. log P eis examined and their properties are interpreted. It is also shown that for those temperatures and pressures in which the main source of opacity is the Thomsons cattering, the HdC mixture is less opaque than the solar one (or the pop. II one). For low temperatures, the low abundance of C will strongly limit the formation of C- in the HdC mixture, thus preventing it from reaching the absorbing importance of H- in the solar one. C in the HdC mixture mimics the behavior of H in the solar one: either as an electron donor, as a maker of molecules or as a source of opacity. The similarity is qualitative only. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

12.
New expansions of elliptic motion based on considering the eccentricitye as the modulusk of elliptic functions and introducing the new anomalyw (a sort of elliptic anomaly) defined byw=u/2K–/2,g=amu–/2 (g being the eccentric anomaly) are compared with the classic (e, M), (e, v) and (e, g) expansions in multiples of mean, true and eccentric anomalies, respectively. These (q,w) expansions turn out to be in general more compact than the classical ones. The coefficients of the (e,v) and (e,g) expansions are expressed as the hypergeometric series, which may be reduced to the hypergeometric polynomials. The coefficients of the (q,w) expansions may be presented in closed (rational function) form with respect toq, k, k=(1–k 2)1/2,K andE, q being the Jacobi nome relatedk whileK andE are the complete elliptic integrals of the first and second kind respectively. Recurrence relations to compute these coefficients have been derived.on leave from Institute of Applied Astronomy, St.-Petersburg 197042, Russia  相似文献   

13.
The production of magnetic monopoles-antimonopoles pairs is expected in the interactions of highly energetic particles in the outer gaps of a pulsar. We estimate upper limit for production of monopoles withm g 104 GeV c –2 ine + e – interactions of the order ee 10–32 cm–2.  相似文献   

14.
The spectrum of the peculiar Bp star HD 36916 has been studied on plates with dispersion 9.7 A/mm and compared with those of Aur, B3V andi And, B8V. A comparison of the observed contours of H, H and of the Balmer discontinuity D with those computed by Mihalas gives the following results: HD 36916: e=0.347, logg=3.8;i And: e=0.383, logg=3.2; Aur: e=0.302, logg=3.6. HD 36916 presents the characteristics of the Si-4200 stars: strong deficiency in helium and probably also in oxygen and nitrogen, strong excess of silicon and strontium; 3984 Hgii is present. Moreover this star also has characteristics which are not common to Si-4200 stars but rather to Mn stars: excess by a factor of ten of the elements of the iron group and an excess larger, probably of the order of 100, for manganese. The star is a member of the Sword subgroup of the Orion association.  相似文献   

15.
Some classic expansions of the elliptic motion — cosmE and sinmE — in powers of the eccentricity are extended to highly eccentric orbits, 0.6627...<e<1. The new expansions are developed in powers of (e–e*), wheree* is a fixed value of the eccentricity. The coefficients are given in terms of the derivatives of Bessel functions with respect to the eccentricity. The expansions have the same radius of convergence (e*) of the extended solution of Kepler's equation, previously derived by the author. Some other simple expansions — (a/r), (r/a), (r/a) sinv, ..., — derived straightforward from the expansions ofE, cosE and sinE are also presented.  相似文献   

16.
The classic Lagrange's expansion of the solutionE(e, M) of Kepler's equation in powers of eccentricity is extended to highly eccentric orbits, 0.6627 ... <e<1. The solutionE(e, M) is developed in powers of (e–e*), wheree* is a fixed value of the eccentricity. The coefficients of the expansion are given in terms of the derivatives of the Bessel functionsJ n (ne). The expansion is convergent for values of the eccentricity such that |e–e*|<(e*), where the radius of convergence (e*) is a positive real number, which is calculated numerically.  相似文献   

17.
Abstract— We describe results of 32 N‐body planetary accretion simulations that investigate the dependence of terrestrial‐planet formation on nebula surface density profile σ and evolution of the eccentricities of Jupiter and Saturn ej,s. Two surface density profiles are examined: a decaying profile with σ ∝ 1/a, where a is orbital semi‐major axis, and a peaked profile in which σ increases for a < 2 AU and decreases for a > 2 AU. The peaked profiles are generated by models of coagulation in an initially hot nebula. Models with initial ej,s = 0.05 (the current value) and 0.1 are considered. Simulations using the decaying profile with ej,s = 0.1 produce systems most like the observed planets in terms of mass‐weighted mean a and the absence of a planet in the asteroid belt. Simulations with doubled σ produce planets roughly twice as massive as the nominal case. Most initial embryos are removed in each simulation via ejection from the solar system or collision with the Sun. The asteroid belt is almost entirely cleared on a timescale of 10–100 Ma that depends sensitively on ej,s. Most initial mass with a < 2 AU survives, with the degree of mass loss increasing with a. Mass loss from the terrestrial region occurs on a timescale that is long compared to the mass loss time for the asteroid belt. Substantial radial mixing of material occurs in all simulations, but is greater in simulations with initital ej,s = 0.05. The degree of mixing is equivalent to a feeding zone of half width 1.5 and 0.9 AU for an Earth mass planet at 1 AU for the cases ej,s = 0.05 and 0.1, respectively. In simulations with ej,s = 0.05, roughly one‐third and 5–10% of the mass contained in final terrestrial planets originated in the region a > 2.5 AU for the decaying and peaked profiles, respectively. In the case ej,s = 0.1, the median mass accreted from a > 2.5 AU is zero for both profiles.  相似文献   

18.
Hansen’s coefficients in the theory of elliptic motion with eccentricity e are studied as functions of the parameter η = (1 − e 2)1/2. Their analytic behavior in the complex η plane is described and some symmetry relations are derived. In particular, for every Hansen coefficient, multiplication by suitable powers of e and η results in an entire analytic function of η. Consequently, Hansen’s coefficients can be in principle computed by means of rapidly convergent series in powers of η. A representation of Hansen’s coefficients in terms of two entire functions of e 2 follows.   相似文献   

19.
Evolutionary masses corresponding to various evolutionary phases of Population I pulsating stars (89 Delta Scuti variables and 155 classical cepheids) are interpolated in the systems of tracks of Iben (1967) and Paczyski (1970). The evolutionary masses are larger in the latter system than in the former one. The uncertainty of the evolutionary mass of a star is estimated, when various evolutionary phases are possible for this star (a smaller evolutionary mass corresponds to a later phase). Semi-empirical period-evolutionary mass-colour (P-M e -C) and period-evolutionary mass (P-M e ) relations are derived for various modes, groups of stars, colour indices (and effective temperature), and evolutionary phases. For Delta Scuti stars, the uncertainty of evolutionary masses calculated from theP-M e relations for different modes, is estimated. The improvement of the evolutionary mass accuracy is estimated, when aP-M e -C relation is used instead of the correspondingP-M e relation. The theoretical and semi-empirical period ratios of radial pulsations derived from theP-M e relations for Delta Scuti stars, are compared. There is a relatively good agreement between theP-M e relations for the two types of Population I pulsating stars, but a gap exists between them. The evolutionary masses of these stars are closer in the two systems of tracks and are derived with a relatively higher accuracy in comparison with their ages.  相似文献   

20.
The hydrodynamics that develops during the infall of the core of a massive star at the end of its hydrostatic evolutionary epoch can have a profound effect on its subsequent dynamical history. In this paper the important processes governing the infall hydrodynamics are explored both semi-analytically and numerically with the aim of explaining the results of large-scale numerical calculations. We focus in particular on the factors responsible for reducing the mass of the inner core. These factors are found to be mainly associated with general relativistic effects and with the production, equilibration, and transport ofv e 's. Semi-leptonicv e emission and absorption are responsible for virtually all of thev e production. They dominate the energy transfer rate between matter andv e 's, but, with the rates being skewed to high energy, they are an importantv e -matter equilibrator only for the high-energy tail of thev e distribution. Neutrinoelectron scattering (NES) plays the dominant role inv e -matter equilibration with the important result that the equilibration is nearly complete by trapping. A careful examination of conditions where the onset of neutrino trapping is occurring indicates that the trapping density is a function of the enclosed mass, increasing with decreasing distance from the core center, and increasing with the extent of thev e -matter equilibration. Though not the dominant contributor to thev e -matter energy transfer rate, NES dominates the matter entropy production rate with another important result that the electron capture rate on free protons is significantly increased before trapping. The result of all of this is a greatly reduced inner core mass by the time of core turn-around. For numerical calculations employing the LLPR equation of state (or something similar), and for precollapse models having iron cores as small as 1.35M (the smallest used by the author), this reduction of the inner core mass leads to the generation of a weak shock which fails to eject mass in a promptffashion. The effect of the small inner core mass on the subsequent dynamical history of the core is unknown.Supported in part by National Science Foundation Grant AST-8408432.  相似文献   

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