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1.
When cosmic quantum mechanics is applied to a double galaxy, the result is mass limits in order for the two galaxies to form a quantum binary system. For a non-relativistic theory (based on the Schrödinger wave equation), the mass limits are: (m g)max 1012 M and (m g)min 1010 M . One possible consequence appears to be a Newtonian gravitational constant that varies with cosmic time, with its value larger in the cosmic past.  相似文献   

2.
On the basis of data on planetary nebula (PN) central star temperatures obtained by measurements in the ultraviolet (UV) range, the empirical calibration dependence between the number of Lyman photons emitted by a central starS and PN diameterD, is constructed. The temperatures of 118 PN central stars are estimated with this dependence. It is shown that the central star masses are distributed in a wide interval from 0.5 to 1.2M . About 60% of all stars have masses <0.6M , about 25% have masses >0.6M and the remainder have masses 0.6M . The averaged empirical tracks of evolution of low-mass (<0.6M ) and massive (>0.6M ) central stars differing considerably from each other are constructed. It is shown that the majority of central stars may possess hot chromospheres (T>2×105 K) which spread for several tens of radii of the central star. The PN originates as a result of ionization of the matter ejected by a red giant at the superwind stage. The cause for this ionization is the UV radiation of the PN central star.  相似文献   

3.
We have discussed, in general, the important physical parameters, likemaximum mass, radius, and the minimum rotation period of self-bound,causally consistent, and pulsationally stable neutron stars (Q-starmodels) by using a realistic stiff EOS (such that, the speed of sound,v P N, or nP=K(E-E a ) n, where K 1 and n =1/(1-2N);where P and E represent respectively, the pressure and theenergy-density, and E a is the value of E at the surface (r = a) of the configuration) within the two constraints imposed by: (i) The minimumrotation period, P rot, for the pulsar known to date corresponds to1.558 ms, and (ii) The maximum number density anywhere inside thestructure for the models described as Q-stars cannot exceed 1nucleon/fm3. By using the empirical formula given by Koranda,Stergioulas and Friedman (1997) (KSF-formula), and imposing constraint(i), we have obtained an upper bound of M max 7.76 M radius a 32.5 km, and the central energy-density around 2.17 ×1014 g cm-3 (for n =1.01). Constraint (ii) provides the minimumrotation period, P rot 0.489 ms for the maximum mass M max 2.4 M, and the central energy-density around 2.20 ×1015 g cm-3 (for n =1.01). The speed of sound at the centre ofthese models approaches 99% of the speed of light `c' (in thevacuum) and vanishes at the surface of the configuration together withpressure. If we relax the maximum Kepler frequency imposed by the fastestrotating pulsar known to date (constraint (i)), in view of certainobservational effects and theoretical evidences, and allow the present EOSto produce larger rotation rates than the 1.558 ms pulsar, the maximummass of the non-rotating model drops down to a value 7.2 M .The higher values of masses ( 7 M ) and radii (31-32 km) obtained in this study imply that these models may representthe massive compact objects like Cyg X-1, Cyg XR-1, LMC X-3, and otherswhich are known as black hole candidates (BHCs). This study also suggestthat the strongest contender for black hole at present might be recurrentnova V404 Cyg (mass estimate 8 -12 M ).  相似文献   

4.
The problem of the survival of a low-mass secondary orbiting a primary that becomes a planetary nebula is studied. The values of the mass of the primary are 1.0, 1.5, and 2.0M ; the values of the mass of the secondary 0.001M , 0.01M and 0.1M . The orbital decay and mass of the secondary due to accretion and gravitational drag in the common envelope are presented. The possible application of the results to V471 Tau, UU Sge, WZ Sge and the Sun-Jupiter system are discussed.  相似文献   

5.
In this paper I present a new evolution model of QSOs luminosity. The model is based on edges distribution of apparent magnitude-redshift of QSOs. After the quasars were formed, the luminosities were increasing until they attained their maximum value atz=2+a, where –0.1a0.6, then the luminosities were decreasing. If the QSOs originate from superconducting cosmic string of same initial massM i 1012 M , the formation epochs are different, most of the quasars start atz cutoff5.6. The most luminous QSOs start at later epochz cutoff5.15. The present sky survey echniques may give us the possibility to see the formation of QSOs at apparent magnitudem V 22.5 by chance of 0.3%.  相似文献   

6.
We have studied the thermonuclear runaways which develop on white dwarfs of 1.205M and 1.358M accreting hydrogen rich material at 10–10 M yr–1. It is found that ignition of this material occurs at densities in excess of about 104 gm cm–3 and that the critical accumulated mass required to initiate the runaway is 0.7(1.5)×10–4 M for a 1.358(1.205)M white dwarf.  相似文献   

7.
It is suggested that the minimum mass of a star at the time of its formation is approximately 0.01M . Making use of this fact and the stellar mass functionF(M) M –, it is found that the hidden mass (or the missing mass) in the solar neighborhood may be explained by the presence of a large number of invisible stars of very low mass (0.01M M<0.07M ).  相似文献   

8.
Steven T. Suess 《Solar physics》1982,75(1-2):145-159
Polar coronal plumes are modeled using concentrations of magnetic flux at 1.01R , and assuming the field is current-free, or a potential field. Identifying the density enhancement of plumes with magnetic flux concentration produces good agreement between 1.01R and 1.10R , for model conditions of a large background magnetic field and a plume separation of 50 000 to 70 000 km at the base. Beyond 1.10R , both plumes and the potential field diverge very nearly as r 2.Also Department of Astrogeophysics, University of Colorado, Boulder, Colo. 80309, U.S.A. Presently visiting Stanford University Institute for Plasma Research, Via Crespi, Stanford, Calif. 94303, U.S.A.  相似文献   

9.
The stationary two-dimensional magnetohydrodynamic solution for the accretion of the matter without pressure into a gravitating centre of a black hole is obtained. It is assumed that the magnetic field far from the collapsed star is homogeneous and its influence on the flow is negligible. Around the star, at the plane perpendicular to the direction of the magnetic field, the dense quasistationary disc is formed, the structure of which in a large extent is determined by dissipation processes. The structure is calculated for (a) a laminar disc with the Coulomb mechanism of dissipation; and (b) a turbulent disc.The estimations of the parameters of the shock which result from the infall of the matter onto the disc are given. In the last section the numerical estimation and approximate character of the radiation spectrum of the disc and the shock are obtained for two cases of 10M and 105 M . The luminosity of collapsed objects withM=10M appears to be about solar, thus its observation is possibly only at the distances less than 300–1000 pc. The collapsed objects in the Galaxy withM=105 M could constitute very bright sources in spectral regions from optical up to X-ray. The spectra of a laminar and a turbulent disc for 10M black hole are very different. The laminar disc radiates primarily in the ultraviolet. The turbulent disc radiates a large part of its flux in the infrared. Therefore, one cannot exclude the possibility that some of the galactic infrared star-like sources are individual black holes in the accretion state.  相似文献   

10.
The contribution to the galactic abundance of He and heavy elements by stellar nucleosynthesis is calculated as a function of time, keeping account of present knowledge about stellar and galactic evolution. A model is used which distinguishes the phase of the contracting halo from the subsequent history of the disc. Various uncertainties involved both in stellar and in galactic evolutionary theory are discussed. The amount of4He produced by stars of different masses and ejected in interstellar medium is fairly well known from stellar theory, while we have assumed its primordial abundance as a free parameter, ranging from 0 up to 0.4. We find that stellar activity provides a significant contribution to the cosmic4He, though not sufficient to explain the observed abundance. The best agreement with observational data (Y 0.26 andY now0.28) is obtained starting with a primordial abundanceY =(0.20–0.23), which is consisten with the Big-Bang theory predictions and with recent observational estimates. The contribution to the abundance of heavy elements depends on the last stellar stages and on the final explosion mechanism, which are only now beginning to be understood. Nevertheless, in the framework of present theories, we individuate a stellar evolutionary scheme reproducing the observedZ abundances for Populationi and Populationii stars, with the correctly estimated Y/Z value. In this scheme, only stars belonging to two narrow mass ranges (10m/m 15 andm/m 80) are allowed to eject metal-enriched matter, possibly with the solar (C+O)/(Si+Fe) ratio.  相似文献   

11.
The Main-Sequence positions as well as the evolutionary behavior of Population III stars up to an evolution age of 2×1010 yr, taking this time as the age of the Universe, have been investigated in the mass range 0.2 and 0.8M . While Population III stars with masses greater than 0.3M develop a radiative core during the approach to the Main Sequence, stars with masses smaller than 0.3M reach the Main Sequence as a wholly convective stars. Population III stars with masses greater than 0.5M show a brightening of at most 2.2 in bolometric magnitude when the evolution is terminated as compared to the value which corresponds to zero-age Main Sequence. The positions of stars with masses smaller than 0.5M remain almost the same in the H-R diagram.If Population III stars have formed over a range of redshifts, 6相似文献   

12.
The evolution of a binary system with components of 10M and 8M is computed through a case B of mass exchange. It is found that after the end of core helium burning, a second stage of mass transfer from the primary occurs. Carbon ignition is prohibited by the large neutrino losses in the degenerated core. The primary remnant, a 1.12M star, ends as a white dwarf. A comparison with the 10M single evolution is made.This research is supported by the National Foundation of Collective Fundamental Research of Belgium (F.K.F.O.) under No. 10303.  相似文献   

13.
A three-component fluid model of the Universe during the recombination era is analysed for = c ( c is the critical density). In addition to the well-known instability of the Jeans mode at 109 M , we find two more unstable modes at 1012 M .  相似文献   

14.
It has been recently established that there exists a maximal red shiftz max for a homogeneous star of given massM. The relationshipz max(M) is obtained for neutron stars in the mass range 0.71M/M 12.06.  相似文献   

15.
Main results of computations of evolution for massive close binaries (10M +9.4M , 16M +15M , 32M +30M , 64M +60M ) up to oxygen exhaustion in the core are described. Mass exchange starting in core hydrogen, shell hydrogen and core helium burning stages was studied. Computations were performed assuming both the Ledoux and Schwarzschild stability criteria for semiconvection. The influence of UFI-neutrino emission on evolution of close binaries was investigated. The results obtained allow to outline the following evolutionary chain: two detached Main-Sequence stars — mass exchange — Wolf-Rayet star or blue supergiant plus main sequence star — explosion of the initially more massive star appearing as a supernova event — collapsed or neutron star plus Main-Sequence star, that may be observed as a runaway star — mass exchange leading to X-rays emission — collapsed or neutron star plus WR-star or blue supergiant — second explosion of supernova that preferentially disrupts the system and gives birth to two single high spatial velocity pulsars.Numerical estimates concerning the number and properties of WR-stars, pulsars and X-ray sources are presented. The results are in favour of the existence of UFI-neutrino and of the Ledoux criterion for describing semiconvection. Properties of several well-known X-ray sources and the binary pulsar are discussed on base of evolutionary chain of close binaries.  相似文献   

16.
The stars in the Main Sequence are seen as a hierarchy of objects with different massesM and effective dynamical radiiR eff=R/ given by the stellar radii and the coefficients for the inner structure of the stars.As seen in a previous work (Paper I), during the lifetime in the Main SequenceR eff(t) remains a near invariant when compared to the variation in the time ofR(t) and (t).With such an effectiveR eff one obtains the amounts of actionA c(M), the effective densities eff(M)=(M)3(M), the densities of action and of energy (or mean presures in the stellar interior)a c(M),e c(M), and the potential energiesE p(M).The amounts of action areA cM k withk1.87 for the M stars,k5/3 for the KGF stars, andk1.83 for the A and earlier stars, representing very simples conditions for the other dynamical parameters. For instancek5/3 means a near invariant effective density eff for the KGF stars, while for such stars the mean densities and coefficients present the strongest variations with masses (M)M –1.81, (M)M0.6.The cases for the M stars (e c(M)M –1) and for the A and earlier stars (betweena c(M)=constant and eff(M)M –1) and also discussed. These conditions for the earlier stars also represent reasonable mean values for the whole stellar hierarchy in the range of masses 0.2M M25M .With all this, one can build dynamical HR diagrams withA c(M), Ep(M), eff M –p , etc., whose characteristics are analogous to these in the photometrical HR diagram. A comparison is made betweenA c(M) from the models here and the HR diagram with the best known stars of luminosity classes IV, V, and white dwarfs.The comparison of the potential energiesE p(M)M –p according to the stellar models used here and the observed frequency function (MM –q (number of stars in a given interval of masses) from different authors suggests the possibility that the productE p(M)(M) is a constant, but this must be confirmed with further studies of the function (M) and its fine structure.There are analogies between the formulation used here for the stellar hierarchy and other physical processes, for instance, in modified forms of the Kolmogorov law of turbulence and in the formulation used for the hierarchy of molecular clouds in gravitational equilibrium. Besides, the function of actionA c(M) for the stars has analogous properties to the relations of angular momenta and massesJ(M) for different types of objects. The cosmological implications of all this are discussed.  相似文献   

17.
It has been shown that the mass of neutron stars obtained from equations of state based on nuclear theory depend upon the number of baryons assembled in it but not on the type of interactions considered. On examining the behaviour of different equations of state based on nuclear theories, a simple polytropic equation of state,P = (K/N)(p –p s)N is proposed. The results obtained forN=1.75 cover the entire range of neutron star masses obtained from the equations of state based on nuclear theories and give a maximum mass of 2.8M . Depending upon various mechanisms for energy output the mass of Crab pulsar is estimated to range from 0.32M to 1.5M . The relation connecting the coordinate mass,M, and the rest mass,M 0, may be written asM/M 0.93 (M 0/M)0.9.  相似文献   

18.
Relativistic, isentropic, homogeneous models are constructed by a method that automatically detects instabilities, and evolutionary tracks of central conditions are shown on a (T, ) diagram. Models heavier than 20M become unstable because of pair creation. Iron photodisintegration causes instability in the mass range between 1.5M and 20M . General relativistic effects bring about the onset of instability in models of 1.2–1.5M when the central density is about 1010 g/cm3. Lighter models become white dwarfs. It is pointed out that general relativistic instability will prevent the formation of neutron stars through hydrostatic evolution and may be relevant in setting off low-mass supernovae.  相似文献   

19.
The relation between molecular clouds, star clusters, and the stellar component of the galactic disk is investigated. According to Elmegreen (1985) bound stellar systems, e.g., open star clusters, can be formed from molecular cloud of mass 104 M . A close encounter with a giant molecular cloud or massive black hole disrupts such stellar systems and forms superclusters. This explains why some open star clusters are so mass-deficient. Unbound stellar systems, e.g., expanding OB associations, are formed from molecular clouds of mass 105 M . When disruptive O-type stars appear the star formation is halted and the cloud is destroyed. An example of the relict of GMC disruption in the solar vicinity is Gould's belt. The velocity dispersion-versus-age relation is also investigated and explained as a consequence of gravitational scattering of stars on GMC, or massive black holes, or as due to recurrent transient spirals.Paper presented at a Workshop on The Role of Dust in Dense Regions of Interstellar Matter, held at Georgenthal, G.D.R., in March 1986.  相似文献   

20.
The theoretical evolution of a first-generation star of 3M after the core helium-exhaustion phase has been investigated. The star displays the character of a double shell burning model. Shell hydrogenburning produces energy mostly by the p-p chain reaction. CN-cycle reaction is only operating in the inner edge regions where sufficient amount of carbon is formed by the 3-reactions. Hence, the shell burning time of the star is longer than that of normal stars, thus lengthening the total evolutionary lifetime of the first-generation stars.Prior to carbon-burning phase, the mass of the complete hydrogen-exhausted region is 1.14M and that of complete helium-exhausted region is 0.83M . A carbon-oxygen core of about 0.87M has developed within the star in which the ratio of carbon to oxygen is about 0.85, but decreases down to a value of 0.50 near the boundary of the core.  相似文献   

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