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1.
New methods are applied to samples of classical cepheids in the galaxy, the Large Magellanic Cloud, and the Small Magellanic Cloud to determine the interstellar extinction law for the classical cepheids, R B:R V:R I:R J:R H:R K= 4.190:3.190:1.884:0.851:0.501:0.303, the color excesses for classical cepheids in the galaxy, E(B-V)=-0.382-0.168logP+0.766(V-I), and the color excesses for classical cepheids in the LMC and SMC, E(B-V)=-0.374-0.166logP+0.766(V-I). The dependence of the intrinsic color (B-V)0 on the metallicity of classical cepheids is discussed. The intrinsic color (V-I)0 is found to be absolutely independent of the metallicity of classical cepheids. A high precision formula is obtained for calculating the intrinsic colors of classical cepheids in the galaxy: (<B>-<V>)0=0.365(±0.011)+0.328(±0.012)logP.  相似文献   

2.
The electron collision excitation rates recently calculated for transitions in Si xiii by Keenan et al. (1987) are used to derive the electron temperature sensitive ratio G(=(f + i)/r and the density sensitive ratio R(=f/i), where i, f, and r are the intercombination (1s 2 1 S – 1s2p 3 P 1, 2) forbidden (1s 2 1 S – 1s2s 3 S), and resonance (1s 2 1 S – 1s2p 1 P), transitions respectively. Also estimated are the values of R in the low-density limit (R 0) as a function of electron temperature. The theoretical G ratio at the temperature of maximum emissivity for Si xiii, G(T m) = 0.70, is in much better agreement with the observed G for the 1985, May 5 flare determined by McKenzie et al. (G = 0.60 ± 0.07) than is the earlier calculation of Pradhan, who derived G(T m) = 0.85. The error in the observed R 0 ratio is so large that both our result and Pradhan's fall within the acceptable limits of uncertainty and hence one cannot estimate which of the two is the more accurate.  相似文献   

3.
We study the stability of motion in the 3-body Sitnikov problem, with the two equal mass primaries (m 1 = m 2 = 0.5) rotating in the x, y plane and vary the mass of the third particle, 0 ≤ m 3 < 10−3, placed initially on the z-axis. We begin by finding for the restricted problem (with m 3 = 0) an apparently infinite sequence of stability intervals on the z-axis, whose width grows and tends to a fixed non-zero value, as we move away from z = 0. We then estimate the extent of “islands” of bounded motion in x, y, z space about these intervals and show that it also increases as |z| grows. Turning to the so-called extended Sitnikov problem, where the third particle moves only along the z-axis, we find that, as m 3 increases, the domain of allowed motion grows significantly and chaotic regions in phase space appear through a series of saddle-node bifurcations. Finally, we concentrate on the general 3-body problem and demonstrate that, for very small masses, m 3 ≈ 10−6, the “islands” of bounded motion about the z-axis stability intervals are larger than the ones for m 3 = 0. Furthermore, as m 3 increases, it is the regions of bounded motion closest to z = 0 that disappear first, while the ones further away “disperse” at larger m 3 values, thus providing further evidence of an increasing stability of the motion away from the plane of the two primaries, as observed in the m 3 = 0 case.  相似文献   

4.
A rigorous theoretical investigation of nonlinear electron-acoustic (EA) waves in a plasma system (containing cold electrons, hot electrons obeying a Boltzmann distribution, and hot ions obeying a nonthermal distribution) is studied by the reductive perturbation method. The modified Gardner (MG) equation is derived and numerically solved. It has been found that the basic characteristics of the EA Gardner solitons (GSs), which are shown to exist for α around its critical value α c [where α is the nonthermal parameter, α c is the value of α corresponding to the vanishing of the nonlinear coefficient of the Korteweg-de Vries (K-dV) equation, e.g. α c ≃0.31 for μ=n h0/n i0=0.5, σ=T h /T i =10, n h0, n i0 are, respectively, hot electron and nonthermal ion number densities at equilibrium, T h (T i ) is the hot electron (ion) temperature], are different from those of the K-dV solitons, which do not exist for α around α c , and mixed K-dV solitons, which are valid around α∼α c , but do not have any corresponding double layers (DLs) solution. The parametric regimes for the existence of the DLs, which are found to be associated with positive potential, are obtained. The present investigations can be observed in various space plasma environments (viz. the geomagnetic tail, the auroral regions, the cusp of the terrestrial magnetosphere, etc.).  相似文献   

5.
The stellar equilibrium equations for given surface pressureP * and temperatureT *, and in the absence of convection, are translated into a nonlinear integral equation, in which the radiusR of the star enters as an eigenvalue. We show that under broad mathematical assumptions on the constitutive equations (equation of state, opacity and energy generation) a global existence and uniqueness property can be formulated. If a valueP M is selected, which restricts the allowed pressure and temperature range |P(r)–P *|+E|T(r)–T *P M (E, arbitrary constant of dimensions of a pressure over temperature), thenat least one solutionP(r),T(r) exists in the pressure-temperature range chosen, for anyR<R E . This solution isunique forR<R c .R E andR c are expressed in terms of the constitutive equations, and of the pressure-temperature range adopted. A physical argument in favour of the stability of this solution is presented.  相似文献   

6.
Three wavelet functions: the Morlet wavelet, the Paul wavelet, and the DOG wavelet have been respectively performed on both the monthly Wolf sunspot numbers (Rz) from January 1749 to May 2004 and the monthly group sunspot numbers (Rg) from June 1795 to December 1995 to study the evolution of the Gleissberg and Schwabe periods of solar activity. The main results obtained are (1) the two most obvious periods in both the Rz and Rg are the Schwabe and Gleissberg periods. The Schwabe period oscillated during the second half of the eighteenth century and was steady from the 1850s onward. No obvious drifting trend of the Schwabe period exists. (2) The Gleissberg period obviously drifts to longer periods the whole consideration time, and the drifting speed of the Gleissberg period is larger for Rz than for Rg. (3) Although the Schwabe-period values for Rz and Rg are about 10.7 years, the value for Rz seems slightly larger than that for Rg. The Schwabe period of Rz is highly significant after the 1820s, and the Schwabe period of Rg is highly significant over almost the whole consideration time except for about 20 years around the 1800s. The evolution of the Schwabe period for both Rz and Rg in time is similar to each other. (4) The Gleissberg period in Rz and Rg is highly significant during the whole consideration time, but this result is unreliable at the two ends of each of the time series of the data. The evolution of the Gleissberg period in Rz is similar to that in Rg.  相似文献   

7.
We present new laboratory data on the multiplets 2s 2 1 S -2s2p 3 P, 2s 22p 2 P - 2s2p 2 4 P, and 2s 22p 2 3 P - 2s2p 3 5 S in nitrogen, oxygen and fluorine, and discuss theZ-dependence of their wave-numbers. These multiplets are very faint in laboratory light sources, but can become prominent in astrophysical sources of low density. Our results confirm the solar identifications of the nitrogen and oxygen multiplets made by Burtonet al. Predicted positions of the corresponding multiplets in neon are given.  相似文献   

8.
We analyze here the behavior of the magnitudes of the F1 and E peaks of the electron density profiles measured by the Radio Science Subsystem of the Mars Global Surveyor spacecraft, as a function of solar zenith angle χ and solar flux. For each of the 658 days of data in the six occultation seasons in the northern hemisphere, we choose one profile to analyze, which is that for which the F1 peak is the median value. We assume that the variations of the measured peak densities can be represented as Aa(cosχ) and as Bb(F10.7), where F10.7 is the usual solar flux proxy, appropriately shifted to the orbital position of Mars. To minimize the effect of solar activity, we divide the data into 6 F10.7 bins, fit the data in each bin, and derive the values of the exponent a and the coefficient AF10.7 for each bin. The median values that we derive for the exponent a is 0.46 for the F1 peak, and 0.395 for the E peak. To minimize the effect of SZA, we divide the data into eight SZA bins, and derive the exponent b and the coefficient Bχ for each SZA bin. We argue that the last three SZA bins should be excluded because the fits were poor, due partly to the small number of data points in each of these bins. If we do so, the median values of b that we derive are 0.27 and 0.40 for the F1 and E peaks, respectively. Finally we derive a 3-parameter fit to all the data, which expresses the variability of the peak densities as a function of a′(cosχ) and b′(F10.7) simultaneously. The fitted values of the exponents a′ and b′ for the F1 peak are 0.45 and 0.26, respectively; for the E peak, the values are 0.39 and 0.46, respectively. We compare our results to Chapman theory, and to those of other investigators.  相似文献   

9.
The modified theories of gravity, especially the f(R) gravity, have attracted much attention in the last decade. In this context, we study the exact vacuum solutions of Bianchi type I, III and Kantowski-Sachs spacetimes in the metric version of f(R) gravity. The field equations are solved by taking expansion scalar θ proportional to shear scalar σ which gives A=B n , where A and B are the metric coefficients. The physical behavior of the solutions has been discussed using some physical quantities. Also, the function of the Ricci scalar is evaluated in each case.  相似文献   

10.
Turova  I.P.  Grigoryeva  S.A. 《Solar physics》2000,197(1):43-56
The ratios I(K 1)/I(H 1) and I(K 3)/I(H 3) were calculated from four semi-empirical models of sunspot umbra. We determined the dependencies of both ratios of such parameters as temperature gradient and atmospheric opacity. A certain influence on the expected ratios I(K 1)/I(H 1) and I(K 3)/I(H 3) can also come from the FIP effect provided it exists in the chromosphere above sunspot umbra. Theoretical and observed values of I(K 1)/I(H 1) and I(K 3)/I(H 3) are compared. It is shown that for one of the sunspots we observed, the values obtained for the ratio I(K 1)/I(H 1) cannot be explained in terms of existing umbra models.  相似文献   

11.
Combining the kinematical definitions of the two dimensionless parameters, the deceleration q(x) and the Hubble t 0 H(x), we get a differential equation (where x=t/t 0 is the age of the universe relative to its present value t 0). First integration gives the function H(x). The present values of the Hubble parameter H(1) [approximately t 0 H(1)≈1], and the deceleration parameter [approximately q(1)≈−0.5], determine the function H(x). A second integration gives the cosmological scale factor a(x). Differentiation of a(x) gives the speed of expansion of the universe. The evolution of the universe that results from our approach is: an initial extremely fast exponential expansion (inflation), followed by an almost linear expansion (first decelerated, and later accelerated). For the future, at approximately t≈3t 0 there is a final exponential expansion, a second inflation that produces a disaggregation of the universe to infinity. We find the necessary and sufficient conditions for this disaggregation to occur. The precise value of the final age is given only with one parameter: the present value of the deceleration parameter [q(1)≈−0.5]. This emerging picture of the history of the universe represents an important challenge, an opportunity for the immediate research on the Universe. These conclusions have been elaborated without the use of any particular cosmological model of the universe.  相似文献   

12.
We augment our scenario for the formation of astronomical objects from macroscopic superstrings by the assumption that the central matter keeps its identity in the fragmentation. From the condition that the angular momentum per mass squared of this matter should be less than the Kerr limit G/c, we obtain upper limits for the ratio of the mass of central black holes M(BH) to the mass M of the host object. This limit is M(BH)/M ≈ 0.001, and, expressed in observed quantities, approximately M(BH)/M ≈ σ2/(v · c) where σ is the r.m.s. velocity, v the rotational velocity and c the velocity of light. The valuesM(BH) agree with the observed behaviour both in order of magnitude and in the variation with velocity dispersion. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

13.
The cornerstones of Boltzmann-Gibbs and nonextensive statistical mechanics respectively are the entropies S BG ≡ −k ∑ i = 1 W p i ln p i and S q ≡ k (1−∑ i = 1 W p i q )/(q−1) (q∊ℜ S 1 = S BG ). Through them we revisit the concept of additivity, and illustrate the (not always clearly perceived) fact that (thermodynamical) extensivity has a well defined sense only if we specify the composition law that is being assumed for the subsystems (say A and B). If the composition law is not explicitly indicated, it is tacitly assumed that A and B are statistically independent. In this case, it immediately follows that S BG (A+B) = S BG (A)+S BG (B), hence extensive, whereas S q (A+B)/k = [S q (A)/k]+[S q (B)/k]+(1−q)[S q (A)/k][S q (B)/k], hence nonextensive for q ≠ 1. In the present paper we illustrate the remarkable changes that occur when A and B are specially correlated. Indeed, we show that, in such case, S q (A+B) = S q (A)+S q (B) for the appropriate value of q (hence extensive), whereas S BG (A+B) ≠ S BG (A)+S BG (B) (hence nonextensive). We believe that these facts substantially improve the understanding of the mathematical need and physical origin of nonextensive statistical mechanics, and its interpretation in terms of effective occupation of the W a priori available microstates of the full phase space. In particular, we can appreciate the origin of the following important fact. In order to have entropic extensivity (i.e., lim N→∞ S(N)/N < ∞, where N≡ numberof elements of the system), we must use (i) S BG , if the number W eff of effectively occupied microstates increases with N like W {{eff}}∼ W ∼ μ N (μ ≥ 1); (ii) S q with q = 1−1/ρ, if W {{eff}}∼ N^ρ < W (ρ ≥ 0). We had previously conjectured the existence of these two markedly different classes. The contribution of the present paper is to illustrate, for the first time as far as we can tell, the derivation of these facts directly from the set of probabilities of the W microstates.  相似文献   

14.
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   

15.
The Bianchi type-V cosmological model with variable modified Chaplygin gas having the equation of state p=Aρ−B/ρ α , where 0≤α≤1, A is a positive constant and B is a positive function of the average scale factor a(t) of the universe [i.e. B=B(a)] has been studied. While studying its role in accelerated phase of the universe, it is observed that the equation of state of the variable modified Chaplygin gas interpolates from radiation dominated era to quintessence dominated era. The statefinder diagnostic pair {r,s} is adopted to characterize different phases of the universe.  相似文献   

16.
An effective Microcanonical Thermodynamics of self gravitating systems(SGS) is proposed, analyzing the well known obstacles thought to prevent the formulation of a rigorous Statistical Mechanics (SM), as those due to the formal unboundedness of available phase space and to the unscreened, long range, nature of the interaction. The latter feature entails the well known inequivalence of statistical ensembles, puts clearly into question the meaning, for these systems, of the Thermodynamic Limit, and rules out the use of canonical and grand-canonical ensembles. As to the first obstacle, we argue nevertheless that a hierarchy of timescales exist such that, at any finite time, the volume of the effectively available region of phase space is indeed finite, and that the dynamics satisfies a strong chaos criterion, leading to a fast, increasingly uniform, spreading of orbits over an effectively invariant subset of the constant (N,V,E) surface; thus leading to the definition of a secularly evolving, generalized microcanonical ensemble, which allows to define an (almost extensive) effective entropy and to derive self-consistent definitions for other thermodynamic variables, giving thus an orthode for SGS. Moreover, a Second Law-like criterion allows to single out the hierarchy of secular equilibria describing, for any finite time, the macroscopic behaviour of SGS. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

17.
Observations of the rapid photometric variability of SS 433 in the BVR bands, obtained on Mt. Maidanak during 12 nights in 1989-90, are presented. The behavior of the U - B, B - V, and V - R color indices is analyzed on the basis of multicolor photoelectric observations. It is found that, both for rapid variability during a night and for variability on the scale of the orbital period, color-brightness relations exist for U-(U - B) and B-(B - V), analogous to the well-known V-(V - R) relation, with a characteristic property: the color indices decrease with increasing brightness. It is shown that the object's reddening upon a brightness decrease is not due only to eclipses. The behavior of the color characteristics can be explained by the interaction of the relativistic jets with the atmosphere around the accretion disk.  相似文献   

18.
High-resolution Fourier Transform Spectrometer sunspot umbral spectra of the National Solar Observatory/National Optical Astronomy Observatory at Kitt Peak were used to detect rotational lines from 19 electronic transition bands of the molecules LaO, ScO and VO, in the wavenumber range of 11 775 to 20 600 cm−1. The presence of lines from the following transitions is confirmed: A 2 Π r1/2 – X 2 Σ +(0, 0; 0, 1), A 2 Π r3/2 – X 2 Σ +(1, 0), B 2 Σ + – X 2 Σ +(0, 0; 0, 1; 1, 0) and C 2 Π r1/2 – A′2Δ r3/2(0, 0; 1, 1) of LaO; A 2 Π r3/2 – X 2 Σ +(0, 0), A 2 Π r1/2 – X 2 Σ +(0, 0) and B 2 Σ + – X 2 Σ +(0, 0) of ScO; and C 4 Σ − – X 4 Σ −(0, 1; 1, 0; 0, 2) and (2, 0) of VO. However, the presence of A 2 Π r3/2 – X 2 Σ +(0, 0) and C 2 Π r3/2 – A′2Δ r5/2(0, 0; 1, 1) of LaO and C 4 Σ − – X 4 Σ −(0, 0) of VO are found to be doubtful because the lines are very weak, and detections are difficult owing to heavy blending by strong rotational lines of other molecules. Equivalent widths are measured for well-resolved lines and, thereby, the effective rotational temperatures are estimated for the systems for which the presence is confirmed.  相似文献   

19.
In this initial study, we propose a new distance function D V involving heliocentric vectorial orbital elements. The function measures differences between: the orbital energies, the angular momentums vectors and the Laplace vectors. In comparison with the widely used D SH criterion of Southworth and Hawkins, D D criterion of Drummond and their hybrid D H by Jopek, the new function contains one invariant with respect to the principal secular perturbation: the orbital energy. The new function proved to be useful in the classification amongst the IAU2003 meteoroids which we searched for streams by D V function and also using D SH and D N -function given by Valsecchi et al. For major streams, the results agree very well. For minor, and near-ecliptical streams the results sometimes differ markedly.  相似文献   

20.
When μ is smaller than Routh’s critical value μ 1 = 0.03852 . . . , two planar Lyapunov families around triangular libration points exist, with the names of long and short period families. There are periodic families which we call bridges connecting these two Lyapunov families. With μ increasing from 0 to 1, how these bridges evolve was studied. The interval (0,1) was divided into six subintervals (0, μ 5), (μ 5, μ 4), (μ 4, μ 3), (μ 3, μ 2), (μ 2, μ 1), (μ 1, 1), and in each subinterval the families B(pL, qS) were studied, along with the families B(qS, qS′). Especially in the interval (μ 2, μ 1), the conclusion that the bridges B(qS, qS′) do not exist was obtained. Connections between the short period family and the bridges B(kS, (k + 1)S) were also studied. With these studies, the structure of the web of periodic families around triangular libration points was enriched.  相似文献   

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