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1.
An equation of state for cold matter at neutron star densities, >1014 gm/cm3, is evaluated. The gas is considered to be a degenerate mixture of neutrons, protons, leptons, hyperons and massive baryons. We derive the equilibrium equations including the effects of nuclear interactions among all the hadrons.  相似文献   

2.
Eigenvalues and normalized wave functions of an electron are derived in the field of a generalized dipole with chargesZ 1 andZ 2 (Z 1+Z 2 0) in the asymptotic region up to the third order (inr 2) where the distance,r 2, between the two charges is small. These asymptotic wave functions render it possible to calculate the asymptotic expansion for the coefficients of a coupled infinite system of second order differential equations arising from a perturbative (analytic) solution to the Schrödinger equation of helium-like ions if the nuclear charge is not less than 2.  相似文献   

3.
The relative abundances of cool neutral hydrogen, carbon monoxide and formaldehyde are studied using all the available observational data in the literature. The obtained mean valuesN H 1/ ,N H 1/N CO,N CO/ are approximately constant in the dark clouds of the solar neighbourhood and in the distant molecular clouds.The observed correlationsN CO,A v and ,A v show that formaldehyde can also be used as an indicator of molecular hydrogen. The ratioN H1/A v depends on densities and decays considerably in the ranges of visual absorptions in which the molecules become detectable (A v 2 mg); an average of /N H 110 is calculated for the dense dark clouds.Indications of systematic temperature gradiens T/A v are found for formaldehyde and neutral hydrogen inside the dark clouds, and qualitative comparisons are made with theoretical quantum mechanics calculations.The observed carbon monoxide and formaldehyde abundances, the free electron layer in the Galaxy, the distribution of neutral hydrogen in different states are only compatible if an ionization rate of 10–16 is accepted, provided presumably by 2 MeV protons of cosmic radiation.Three main states for neutral hydrogen and dust are identified from different kinds of observational data (21 cm line in emission, absorption in galactic radio sources and self-absorption in the hot gas background): (1) a homogeneous intercloud stratum of tenuous gas and dust with a galactic halfwidth of 350 pc and mean parametersn H=0.2 atom cm–3, spin temperatureT s 10000 K andn d 0.3 mg kpc–1; (2) cool gas and dust concentrated in spiral features with a galactic half-width of less than 100 pc, probably forming clouds with diffuse and indefinite limits, with mean parametersn H2 atom cm–3,T s <1100 K (probable average,T s =135 K) andn d 3 mg kpc–1; (3) dense gas and dust clouds with a mean diameter of 7 pc and mean parametersn H700 atom cm–3 (90% in a molecular state),T s 63 K andn d 1 mg pc–1 on which molecules as CO and H2CO are formed.The application of the Jeans criteria for gravitational instability shows that the dense clouds are gravitationally bound while the gas in the intermediate state (2) can be protected against collapse by the total internal energy in the medium increasing due to cosmic rays and the magnetic field in the Galaxy.The observed velocity halfwidths and galacticZ-halfwidths in states (1) and (2) are compatible with a total mass density in the galactic layer of 90M pc–2 (gas plus stars) according to the barometric equation.The relative abundancesN H 1/N CO, calculated from C12O and C13O data and comparisons with studies in the 21 cm emission line, show that the antenna temperatureT A + in the 2.6 mm line of C12O is a good indicator of the cool gas densities in the Galaxy. The possible application of this for studies in galactic structure is discussed and hypothetical distributions of carbon monoxide in the zones outside the galactic planeB=0° are presented.From a synthesis based on the results obtained, a cycle is postulated for the neutral hydrogen in the Galaxy: condensation and cooling of gas molecular formation gravitational collapse and star formation gas dissipation and heating by cosmic rays and UV radiation.  相似文献   

4.
The rotation of a compressible inviscid fluid disc of (1) slowly varying density or (2) nonuniform density (cold gas approximation) or (3) nonuniform density (hot, but tenuous) is considered. Perturbation methods for solving the basic equation for conservation of vorticity are used. It is found that steady state conditions are realized when vortex waves and differential rotation (jet streams) coexist; special solutions for these vortex waves are obtained. For one of these solutions, a given jet stream and its associated vortex (only one vortex per jet allowed) wave can exist only at certain discrete orbital distances, given by a geometric progressionA n wheren is an integer andA is a constant. This progression is a good representation for the distances of planets and satellites, with small orbital inclinations, from their respective parent bodies. Certain other solutions for the vortex wave yield streamlines that are logarithmic spirals. Some justifications are given for applying the model to the dynamics of hurricanes and spiral galaxies. Comparisons with observations are surprisingly favorable.The possible role of the jet streams and the steady state long vortex waves (a cooperative-vortex phenomenon) in the formation and evolution of the solar system is also discussed. Comparisons are made with the von Weizsäcker (1944 and Chandrasekhar, 1946) model of turbulent eddies in the solar nebula and with the particle (asteroidal) jet streams of Alfvén and Arrhenius (1970a, b).  相似文献   

5.
As previously shown (Rabe, 1970), two classes of small periodic librations exist, in the plane, elliptic restricted problem, for an infinite sequence of easily specified oscillation frequenciesZ j . The present paper considers the dependence ofZ on the eccentricitye of the primary motion, in addition to its dependence on the mass parameter , and determines the resulting relations between ande, for any given periodic frequencyZ j . These relationships are obtained from the conditionD (Z j ,, e)=0, where the basic determinantD has been expanded up to terms of orderZ 20, 5, ande 4.Presented at the Conference on Celestial Mechanics, Oberwolfach, Germany, August 27–September 2, 1972.  相似文献   

6.
IntegratedUBV colours have been computed for synthetic clusters older than one billion years and for two chemical composition: (a)Y=0.30;Z=10–4 and (b)Y=0.30;Z=10–2, taking into account the contribution to the integrated light of Main Sequence, subgiant, red giant and horizontal branch stars. It has been found that integrated colours depend onZ and allow an estimate of the metal content, however not generally. Horizontal branch stars contribute to the integrated colours of clusters not significantly and the contribution of stars in more advanced phases (e.g., asymptotic branch stars) is almost negligible.Old clusters in LMC and SMC have been studied in terms of colour calibrations and this analysis has been supplemented, when possible, by photometric and spectroscopic data of individual stars. It was found that in the LMC clusters withZ=10–2 andt>5×109 yr are lacking, clusters with relatively blue colours are similar, both in age and chemical composition, to the halo galactic globular clusters. Moreover, there is a group of clusters with 1×109t5×109. In the SMC clusters withZ=10–2 andt>5×109 yr are lacking and clusters with 1×109t5×109 are rare. Clusters with relatively blue colours are interpreted with the following parameters:t=5×109 yr, 10–4Z10–3 andY=0.20.The implication of these results on the chemical history of the two galaxies is discussed.  相似文献   

7.
In the last four years we have carried out a number of studies on the radiative and collisional processes in theA 2 i state of CN. Many of these of interest to those studying planetary atmospheres, comets and solar spectra are summarized in this paper. Data for CNA 2 i fluorescence lifetimes and quenching rates, and collisional energy transfer between CNA 2 i andX 2+ are reported. Detailed comparisons and a discussion of the results may be found in several already published papers.  相似文献   

8.
A comparison between model atmosphere grids with and without metal blanketing has been performed in the low-temperature range (T eff=6000 K to 10000 K) and for different metal contents (logA=0, –1, –2;A=scaled solar abundance). ForA10–1 andT eff7000 K, the Johnson colour indicesU-B andB-V, together with the Strömgrenu-b, b-y and the bolometric correction (BC) are little affected by metal blanketing ( mag<0 . m 04). On the other hand, the trend of the physical quantities and them 1 andc 1 colour indices reflect the inadequateness of the models even withA=10–2 andT eff=9500 K, where hydrogen line blanketing is expected to dominate. This fact discourages once and for all the use of metal unblanketed atmospheres other than for comparison of colour indices or the calculation of bolometric corrections for Population II A-F spectral types.  相似文献   

9.
Modified similarity method has been used to study the propagation of spherical-variable energy blast waves through a self-gravitating gas. For an energy inputE =E 0t4/3, whereE is the energy released up to timet andE 0 is a functional constant, the similarity solutions correct up to third approximation have been obtained. It is found that the effects of self-gravitational forces are of third order. An increase in the parameterA 2 (characterising the gravitational field) increases the shock velocity.  相似文献   

10.
The minimum-propellant deterministic guidance law for bounded-thrust, constant jetexhaust velocity, spacecrafts is developed using the neighboring extremal theory. Minimization of the first-order variation in cost between a multi-burn nominal extremal and the perturbed trajectory eliminates all correction strategies except small changes in the nominal thrust-on, thrust-off times and small rotations of the thrust vector. Optimal values of these corrective controls for fixed values of initial state deviations, x 0, are found by minimizing the second variation in cost subject to the variational state and adjoint equations — an accessory minimum problem. The solution takes the linear feedback form u=A –1 22 A 21x 0, where the matricesA 22 andA 21 are functions only of transition matrices calculated along the nominal trajectory. The solution is applied to a three-burn Earth-Mars transfer.  相似文献   

11.
R. W. Komm 《Solar physics》1995,156(1):17-28
I study the temporal variation of the solar rotation on time scales shorter than the 11-year cycle by analyzing the daily Mt. Wilson Doppler measurements from 1967 to 1992. The differential rotation is represented by the three coefficients,A, B, andC, of the following expansion: =A +B sin2() +C sin4(). TheA, B, andC time series show clearly the 11-year solar cycle and they also show high-frequency fluctuations. The Hurst analysis of these time series shows that a Gaussian random process such as observational noise can only account for fluctuations on time scales shorter than 20 days. For time scales from 20 days to 11 years, the variations of A give rise to a Hurst exponent ofH = 0.83, i.e., the variations ofA are persistent. The temporal variations ofB show the same behavior asC, which is different fromA. From one to 11 years, theB andC variations are dominated by the 11-year cycle, while for time lags shorter than about 250 days, theB andC fluctuations give rise to a Hurst exponent ofH = 0.66, which lies betweenH = 1/2, of a Gaussian random process, and the exponent of the persistent process shown byA. An analysis of the equivalent coefficients of the first three even Legendre polynomials, computed usingA, B, andC, provides additional information. For time scales between 100 and 1000 days, the ranges,R/S, of Legendre polynomial coefficients decrease with increasing order of the polynomials which suggests that the persistent process operates mainly on large spatial scales. The Hurst exponent ofH = 0.83 for variations inA is the same asH for monthly sunspot numbers with time scales between 6 months and 200 years and for14C radiocarbon data with time scales between 120 years and 3000 years, previously analyzed by other authors. The combined results imply that the underlying solar process shows the same persistent behavior for time scales as short as about 20 days up to time scales of a few thousand years.Operated by the Association of Universities for Research in Astronomy, Inc. under cooperative agreement with the National Science Foundation.  相似文献   

12.
Global input parameters for a Hauser-Feshbach calculation of astrophysical nuclear reaction rates are evaluated; wherever possible they are expressed as systematic functions of nucleon numbersN andZ rather than mass numberA. Average (n, ) cross-sections at 30 keV are calculated for all stable nuclei and nuclei with lifetimes 1 yr, taking into account the effects of width fluctuations. Agreement with experimental results is generally obtained to within 70%, but systematic discrepancies arise for even-even target nuclei between neutron shell closuresN=50 andN=82. A N curve for thes-process nuclei is in good agreement with theoretical predictions, except for a possible anomalous peak aroundA=180.  相似文献   

13.
The Franck-Condon (FC) factors (transition probabilities) andr-centroids have been evaluated by the reliable numerical integration procedure for the bands of the A6+ X 6+ system of astrophysical molecule CrH, using a suitable potential. The dissociation energyD 0 0 = 2.3 eV for the electronic ground state of CrH has been estimated by fitting the Hulburt-Hirschfelder function to the experimental potential energy curve, using the correlation coefficient.  相似文献   

14.
The solar spectrum of wavelength 350–800 nm has been measured for the four seasons. The intensity of the solar radiation in W m-2 nm-1 has been calculated and used to estimate the monochromatic optical depth of Bahrain's sky. It was found that the optical depth (i.e., extinction coefficient,k) is least in winter and highest in summer. Comparison of the hourly variation of the optical depth between Bahrain's atmosphere and that of Dhahran (Saudi Arabia) shows that the abundance of small size particles in the former is more than in the latter. This causes more extinction effect in Bahrain than in Dhahran, especially in the wavelengths 350–525 nm. The relation betweenk and for each season in Bahrain is in the formk =A n , whereA is a constant andn is a negative integer, is reported in this study.  相似文献   

15.
Vibrational transition probabilities: namely, Franck-Condon factors andr-centroids, have been evaluated using an approximate analytical method for theB-A system of MgO. Morse potential energy curves forB 1+ andA 1 states of MgO have been constructed by use of the latest spectroscopic data. The value ofr-centroids for the band have been found to decrease linearly with the corresponding wavelength. We show results for six new bands in the umbral spectrum of the Sun.  相似文献   

16.
With the available data in planets, stars and galaxies, it is studied the functions of angular momentaJ(M) and amounts of actionA c(M) (associated to the non rotational terms in the kinetic energy). The results indicate that independently of how are these functionsJ(M),A c(M) their ratioA c/J remains a near invariant. It is independent also from the type of angular momenta: intrinsic spins of the bodies or the total angular (orbital) momenta of the bodies forming a system; for instance, the Solar System and the planets.The relationA c(M) for the Solar System are analogous to these in the FGK stars of the main sequence, and the relationJ(M) (also for the Solar System) is analogous to the lower possible limit for binary stars.The different types of binary stars from the short period, detached systems to contactary systems, gives a range of functionsJ(M),A c(M) that are the same that one can expect in stars with planetary systems. According to the detection limits given for planetary companions by Campbell, Walker and Yang (1988) (masses of less than 9 Jupiter masses and orbital periods of less than 50 years) we calculate the limits forJ(M) andA c(M) This gives a lower limitA c/J 1 associated to stars with planetary systems as 61 Cygni and to short period detached binaries. The upper limitA c/J 16 correspond to planetary systems as the ours and probably to cataclysmic binaries. There are reasons to suspect that systems as the ours and in range 4 A c/J 16 (with a lower limit analogous to contactary binaries as Algols and W Ursa Majoris) must be the most common type of planetary systems. The analogies with the functionsJ(M)A c(M) for galaxies suggest cosmogonical conditions in the stellar formation.Independently of this, one can have boundary conditions for the Jacobi problem when applied to a collapsing cloud. Namely, from the initial stage (a molecular cloud) to the final stage (a formed stellar system: binary or planetary) the angular momenta and amounts of action decayed to 10~4 the initial values, but in such a form thatA c(t)/J(t) remains a near invariant.  相似文献   

17.
A nuclear reaction network of 903 different, strong and electromagnetic reactions, linking 107 chemical constituents is used to study the elements synthesized in the neutron rich material, ejected in supernova explosions. A large number of three body reactions virtually eliminates the usual bottle neck at theA=5 mass gap.For initially high temperatures and densities,T=1010K and =7×108 gm/cm3, with expansion time scales of 10–3–10–2 sec, three differentn top ratios,n/p=4,n/p=3/2, andn/p1, are considered for the ejected matter. In all three cases, the material synthesized is preponderantly heavy. For then/p=4 model, the conditions at the charged particle freeze-out are ideal for the r-process. The onset of this rapid neutron capture phase is explicitly shown with a sequence of time lapse abundance plots.  相似文献   

18.
A non-linear Schrödinger equation which characterizes the non-linear electrostatic waves in collisionless turbulent plasma is derived. Detailed analysis of this equation for the non-linear Langmuir waves is presented to show how the ion dynamics affects the envelope behaviour of these waves. Necessary condition for the existence of Langmuir envelope solitons is found to bek 2 D 2 (m/M);k being the characteristic wave number, D the electron Debye length andm andM the electron and the proton mass.Paper dedicated to Professor Hannes Alfvén on the occasion of his 70th birthday, 30 May, 1978.  相似文献   

19.
Rapid proton capture is supposed to be responsible for the synthesis of a number of proton-rich nuclei. This process of hydrogen burning is considered here for mass elements, the atomic numbers of which range fromZ=10 toZ=20. The possible site for this process is assumed to be the outer envelope of the supernova at a proton number density (n p )ranging fromn p =1022 cm–3 ton p =1028 cm–3 at temperatures in the range ofT=2–3×109 K.The capture path is determined by considering that a dynamical equilibrium between (p, ) and (,p) reactions exists between the reacting nuclei. In this situation, the abundances of elements become proportional to the lifetime of + decaying nuclei at the waiting points.It is suggested that these rapid proton-capture reactions are responsible for the production of a number of nuclei in the rangeA40 during supernova outbursts.  相似文献   

20.
The effect of a prevalent magnetic field on static and uniformly rotating self-gravitating cylinders of infinite length is examined. The magnetic field is assumed to consist ofH andH z components, which are taken to be functions of the radial coordinate alone. A variety of magnetic-field configurations are shown to be admissible solutions of equations of motion, from which some feasible cases are presented. A particular magnetic-field configuration having bothH andH z components is studied in detail. The configuration is such that the assumption of a polytropic equation of state reduces the equation governing the density function to a non-homogeneous cylindrical analogue of the Lane-Emden equation for spherical polytropes. The homogeneous case is also studied and shows interesting magnetic-field patterns.  相似文献   

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