首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 578 毫秒
1.
By considering the relativistic expression for isothermal NS cores,T·e /2 = constant, we have shown that some of the standard equations of state, when applied to NS cores, correspond to constancy of some adiabatic exponents. It has been shown that the equation of state,P=KE, corresponds to 1 = to 2 = 3 1 +K and the equation of state, dP/dE=K, corresponds to 3 1 +K. The conditions under which different equations of state represent isothermal cores have been obtained: For isothermal NS, the local temperatureT, can be expressed in terms of pressureP, energy densityE, and rest mass density . For example: (a)P =KE :T = constant × (E/); (b)P=KE :T = constant × (P/); (c) dP/dE =K :T K ; (d) = 2 :T = constant × (P/E); and (e) = 3 :T = constant × (P/)1/2. Equation of state corresponding to = 2 is obtained as:P=E/ln(K/E) and the equation corresponding to = 3 comes out as:E=P ln(K/P). Core-envelope models can be developed for these two cases. When core equation corresponding to = 2 or = 3 is used in the core, we can ensure the continuity of dP/dE at the core-envelope boundary, along with the continuity ofP, E, , and . The parameters of isothermal NS cores corresponding to the cases = 2 and = 3, have been obtained. The maximum mass of these NS cores comes out to be 2.7 .  相似文献   

2.
Two spherically symmetric time-dependent Green's functions of the equation of transport for cosmic rays in the interplanetary region are derived by transform techniques. The solar wind velocity is assumed radial and of constant speedV. In the first model the radial diffusion coefficient =0 r (0 constant), and in the second solution =0= constant. The solutions are for monoenergetic, impulsive release of particles from a fixed heliocentric radius. Integration of the solutions over timet, fromt=0 tot=, gives the steady-state Green's functions obtained previously.  相似文献   

3.
The periodogram analysis of theV observations of the Scuti star HR 1225 has been carried out. Two frequencies of 6.415 cd (P 0=0 . d 1558) and 8.418 cd (P 1=0 . d 1188) have been determined. The period ratio ofP 1/P 0=0.762 indicates radial pulsation. The absolute magnitude, effective temperature and mass of the star are derived to be 1 . m 05, 7600 K and 1.9M , respectively.  相似文献   

4.
All knownV data from the literature for the Scuti star HR 1170 have been reanalysed by using single-frequency Fourier and multiple-frequency least squares analysis. The calculated periods areP 1=0 . d 09942 andP 2=0 . d 08392. The second frequency has not been found before and gives better residuals and almost constant amplitudes for the individual data sets. The period ratio andQ values indicate that this star is not pulsating in pure radial modes.  相似文献   

5.
A small particle moves in the vicinity of two masses, forming a close binary, in orbit about a distant mass. Unique, uniformly valid solutions of this four-body problem are found for motion near both equilateral triangle points of the binary system in terms of a small parameter , where the primaries move in accordance with a uniformly-valid three-body solution. Accuracy is maintained within a constant errorO(8), and the solutions are uniformly valid as tends to zero for time intervalsO(–3). Orbital position errors nearL 4 andL 5 of the Earth-Moon system are found to be less than 5% when numerically-generated periodic solutions are used as a standard of comparison.  相似文献   

6.
In this paper, we present VRc photometric observations of four dwarf cepheids: YZ Boo (P = 0 . d 104, V = 0 . m 5), AD CMi (P = 0 . d 123, V = 0 . m 5), XX Cyg (P = 0 . d 135, V = 0 . m 5), EH Lib (P = 0 . d 088, V = 0 . m 7). The light curves were obtained at West Mountain Observatory, Provo, Utah on 14 nights from 1983 through 1986 and contain 589 data points in each of theV andR bands in the Cousin photometric system. A detailed study of these stars, based on the present light curves, will be published separately.  相似文献   

7.
Exact corotations are equilibrium points in the phase space of the asteroidal elliptic restricted problem of three bodies averaged over the synodic period, at a mean-motions resonance. If the resonant critical angle is =(p+q) jup –p–q, exact corotations are double resonant motions defined by the conditionsd/dt=0 andd(– jup )/dt=0. The first condition is characteristic of the periods resonance(p + q) : p and the second one is a secular resonance equivalent to that usually known as thev 5-resonance. This paper presents the symmetric solutions =0 (mod ), = jup (mod ). Corotations have a coherence property which is unique in non-collisional Celestial Mechanics: An elementary calculation shows that, in the neighbourhood of these solutions, the motions cluster aroundp independent longitude values and are, in each cluster, as close together as and are close to the equilibrium values.  相似文献   

8.
We prove existence and multiplicity of T-periodic solutions (for any given T) for the N-body problem in m (any m 2) where one of the bodies has mass equal to 1 and the others have masses 2,..., N , small. We find solutions such that the body of mass 1 moves close to x = 0 while the body of mass i moves close to one of the circular solutions of the two body problem of period T/k i, where ki is any odd number. No relation has to be satisfied by k 2,...,k N.  相似文献   

9.
Relativistic stellar structures can be obtained both analytically and by computation, but all these models do not stand the tests of physical reality. It is shown that for a physically reasonable solution d/dr -r and d(e v /dr r near the centre, d(P/)/dr<-0 and (dP/d)>-(P/). If we change the variabler tox=Cr 2, whereC is a constant, the field equations are reduced to a form which is easier to solve. A new set of exact solutions is obtained by consideringe v (1-x) n . Also, a method has been given to obtain generalized solution.It is shown that the solution discussed by Durgapal and Rawat (1980) is the only exact solution which in its most generalized form for a given density distribution stands all the tests of physical reality and for which both (P/) and (dP/d) decrase with increasing value ofr.Neutron star model is proposed by assuming >-2×1014g cm–3. Two specific cases are considered, viz.,P<-1/3 and dP/d<-1, respectively. The structures are found to be bound and stable under radial perturbations. The models have been studied for slow rotation and the mass of the Crab pulsar has been estimated for different mechanisms.  相似文献   

10.
A quasi-steady 1-D hydrodynamic model, with mass addition, has been used to study the various modes of interaction of the solar wind with a medium-bright, H2O-dominated comet (such as P/Halley) approaching the Sun.At large heliocentric distances (d 5 AU) the solar wind penetrates unimpeded on to the surface. As the comet moves further in, mass loading of the solar wind by heavy ions from the fledgling cometary atmosphere causes it to slow down, thereby causing a significant enhancement of the interplanetary field. Still further in at d 3.14 AU, as the mass loading reaches a critical value, a collision-less standing shock is formed in the solar wind upstream of the nucleus. As d decreases further, the distance of this shock from the nucleus increases. The cometary atmosphere becomes dense enough to stand off the solar wind ahead of the nuclear surface and form a well defined tangential discontinuity surface (or ionopause) only when d reaches the value 2.65 AU. When d 2.65 AU an inner shock could, in principle, also form within the cometary ionosphere, although its existence would depend on the detailed thermodynamics of the cometary ionosphere. Resolution of this question is beyond the scope of the present analysis.The conclusions of the present study would be qualitatively valid for other comets having sizes, surface optical properties and chemical compositions, different from those adopted here. The helio-centric distances at which the various transitions take place from the one mode of solar wind interaction to another, would, of course, be different, with all these distances being smaller for less active comets.  相似文献   

11.
Sommaire Les lois du mouvement dans une variété riemannienneV 4 peuvent être déduites d'un principe de moindre action. Nous établissons dans cet article l'équivalence des relations ds=0 et dL=-L k dk, où ds 2=L 2 est une métrique riemannienne et d k /dt une fonction homogène de degré 1 des variables dx i/dt qui définit un espace de Weyl. Ce théorème permet de ramener une théorie de jaugen à un principe de moindre action. Il peut être utilisé dans la théorie de la double métrique de Dirac, obtenue en choissant la théorie des grands nombres comme condition de jauge. Une fibration de l'espace physiqueV 3 basée sur le théorème de Huyghens permet de déduire les propriétés dynamiques des particules des propriétés des photons dansV 3, et constitue en ce sens une unification des propriétés dynamiques des particules.
The laws of motion in a RiemannianV 4 manifold can be deduced from the principle of least action. We state in this work the equivalence between the equations ds=0 and dL=-L k dk, where ds 2 =L 2 is the Riemannian metric and d k /dt the homogeneous functions of first degree of the dx i/dt which define a Weylian space. This theorem can then reduce a gauge theory to a principle of least action. It can be used in the double metric theory of Dirac, obtained by means of the Large Number Hypothesis as a gauging condition. A fibration of the physical spaceV 3 based on Huyghens' theorem allows the deduction of the dynamical properties of particles by means of the properties of photons inV 3, and constitutes in this way an unification of the dynamical properties of particles.
  相似文献   

12.
Fluctuations in the angle-of-arrival of a luminous wavefront are investigated by placing a narrow slit over the image of the solar limb, and observing the entrance pupil through this diaphragm. Measurement of the standard deviation AA of these fluctuations, in a direction perpendicular to the solar limb, provides sufficient information to estimate an absolute parameter characterizing the seeing, i.e. Fried's parameter r 0 or the equivalent parameter L C N 2(h) dh which gives the integral, over an atmosphere thickness L which depends on the spatial and angular filterings performed by the slit, of the structure constant C N 2 characterizing fluctuations in the air's refractive index. Simultaneous estimations of AA 2 and L C N 2 (h) dh permit a linear relationship to be established between these two quantities. The result is interpreted theoretically by integration of the two-dimensional power spectrum for the angle-of-arrival fluctuations. The influence of filtering effects is discussed.Such a calibration can be performed for a given telescope and slit, enabling the system to be used as a seeing monitor.  相似文献   

13.
In a simple approximation, the evolution of a stellar system can be described in terms of the solutions to a diffusion equation for motion in a harmonic potential. This paper presents a discussion and characterization of the normal modes for this equation. These solutions are of particular interest in that they provide a simple example of the interplay between dynamical and relaxation phenomena. For the case of a large system, in which the relaxation timet r is much greater than the dynamical timet d,there exists a well-defined sense in which the effects of relaxation may be viewed as a perturbation of motion in the fixed field: the dynamical effects give rise to a purely oscillatory behavior, whereas collisions among stars provide a dissipative mechanism that drives the system towards the unique isothermal equilibrium. Alternatively, the presence of the fixed potential serves to alter the e-folding time for the various modes. In the limit thatt r t d , all characteristic relaxation times are essentially doubled. This suggests a danger in the use of velocity space equations to model the effects of evaporation.  相似文献   

14.
The scope of the present paper is to provide analytic solutions to the problem of the attitude evolution of a symmetric gyrostat about a fixed point in a central Newtonian force field when the potential function isV (2).We assume that the center of mass and the gyrostatic moment are on the axis of symmetry and that the initial conditions are the following: (t 0)=0, (t 0)=0, (t 0)=(t 0)=0, 1(t 0)=0, 2(t 0)=0 and 3(t 0)= 3 0 .The problem is integrated when the third component of the total angular momentum is different from zero (B 1 0). There now appear equilibrium solutions that did not exist in the caseB 1=0, which can be determined in function of the value ofl 3 r (the third component of the gyrostatic momentum).The possible types of solutions (elliptic, trigonometric, stationary) depend upon the nature of the roots of the functiong(u). The solutions for Euler angles are given in terms of functions of the timet. If we cancel the third component of the gyrostatic momentum (l 3 r =0), the obtained solutions are valid for rigid bodies.  相似文献   

15.
To improve the scaling parameter controlling the impact crater formation in the strength regime, we conducted impact experiments on sintered snow targets with the dynamic strength continuously changed from 20 to 200 kPa, and the largest crater size formed on small icy satellites was considered by using the revised scaling parameter. Ice and snow projectiles were impacted on a snow surface with 36% porosity at an impact velocity from 31 m s−1 to 150 m s−1. The snow target was sintered at the temperature from −5 °C to −18 °C, and the snow dynamic strength was changed with the sintering duration at each temperature. We found that the mass ejected from the crater normalized by the projectile mass, πV, was related to the ratio of the dynamic strength to the impact pressure, , as follows: , where the impact pressure was indicated by P = ρtC0tvi/2 with the target density of ρt, when the impact velocity, vi, was much smaller than the bulk sound velocity C0t (typically 1.8 km s−1 in our targets). The ratio of the largest crater diameter to the diameter of the target body, dmax/D, was estimated by calculating the crater diameter at the impact condition for catastrophic disruption and then compared to the observed dmax/D of jovian and saturnian small satellites, in order to discuss the formation condition of these large dmax/D in the strength regime.  相似文献   

16.
Liouville's theorem for radiation, of which the generalized étendue is a consequence, implies 2 d2 d2 A = constant along the ray path, where is the refractive index and d2 and d2 A are the ranges, respectively, of solid angle and of area that define a ray (actually a bundle of rays). Implications of this concept on the propagation of radio waves from the actual to the apparent source in the solar corona (i.e., the scatter image of the true source) are discussed. The implications for sources of fundamental plasma radiation include: (1)The observed solid angle (defining the directivity) and apparent area A of the source are compatible with Liouville's theorem only if the apparent source (the scatter image of the true source) corresponds to the envelope of subsources with a small filling factor f. (2) The brightness temperature T Bof the actual source is greater than that of the apparent source by f -1. (3) For sources of fundamental plasma radiation the factor f is very small ( 10-2). (4) A long-standing discrepancy between the observed low value of T B at meter/decameter wavelengths for the quiet Sun and the known coronal temperature may be resolved by noting that the implied coronal temperature is given by T B f and that the factor f must be significantly less than unity.A brief discussion is included of the relation between Liouville's theorem, the generalized étendue, Milne's laws, occupation numbers, extension in phase, and suppression of emission by a medium with refractive index unequal to unity.  相似文献   

17.
Observational data of the solar diameter in Italy during 1876–1937 and in Greenwich during 1851–1937 were analyzed. The Whittaker operator with different smoothing coefficients was used. The average data sets for the analysis of the possible oscillations of the solar diameter during 1876–1937 were obtained. Average values of the solar radius R(t) and absolute values of its time derivative ¦dR(t)/dt¦ were compared with the Wolf number, W(t), and with the integral A(t) = 0 t W(t)dt + constant. A good correlation r(R, W) = ¦dR(t)/dt¦, W(t) and r(R, A) = R(t), A(t) was found. It was shown that the frequency spectra of R(t) and A(t) are similar. It was found that during odd 11-yr cycles, the solar diameter decreases, whereas during even cycles it increases. A hysteresis-like behavior in the variation of R(t) during the 22-yr solar magnetic cycle was demonstrated.  相似文献   

18.
G. H. Fisher 《Solar physics》1982,113(1-2):307-311
We explore the dynamics of chromospheric condensations driven by evaporation during the impulsive phase of solar flares. Specifically, we find that the maximum chromospheric downflow speed obeys the approximate relation d = 0.4 (F/ ch )1/3, where F is that part of the flare energy flux driving chromospheric evaporation, and ch is the mass density in the preflare chromosphere just below the preflare transition region. This implies that chromospheric downflows as measured by H asymmetries may be a powerful probe of flare energetics.  相似文献   

19.
The increasing central concentration of the Sun with age modifies the acoustic eigenfrequencies. In particular, the frequency separation d l =3(2l+3)–1v n,l –v n–1,l+2 for modes with l + 1/2 n decreases as nuclear reactions augment the molecular-weight gradient in the energy-generating core. If, for example, the Sun were older than is generally believed, one might therefore expect d l to be smaller than current theoretical predictions. On the other hand, to ensure that the luminosity is consistent with observations, the presumed initial hydrogen abundance would need to be enhanced, thereby reducing the resultant molecular-weight gradient. Thus there is some degree of cancellation of the two major factors that determine d l .Various authors have either reported directly on the sensitivity of d l , or have provided the information from which it can be calculated. We have added our own computations. There is broad agreement amongst the results: d l diminishes with the presumed age of the Sun at the rate of about 1 Hz per Gy for l = 0; the magnitude of the rate appears to decline with increasing l.  相似文献   

20.
We have studied the behavior of the inner motions of OH, H2CO, and CO molecular clouds. This study shows the existence of two main components of these clouds: the narrow one, associated to dense small clouds and a wide one representing the large diffuse clouds seen in neutral hydrogen, the large clouds are the vortex and intermediate state between turbulent and hydrodynamic motions in the Galaxy.For the dense clouds with sizesd<10 pc we have found a relationship d 0.38 consistent with the Kolmogorov law of turbulence; the densities and sizes of these clouds behave asnd –1. This last relation for these molecular clouds is compared with theHII one. Also, we discuss the effects of the inner magnetic field in these clouds.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号