Hidden mass in the solar neighborhood

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 ).     

On Low-Mass, Strange Quark Stars with a Crust

Low-mass strange stars with a crust are investigated within the framework of the bag model. The crust, which consists of degenerate electrons and atomic nuclei, has a limiting boundary density _cr , which is determined by the mass of the crust, and it cannot exceed the value _drip = 4.3·10¹¹ g/cm³, corresponding to the density at which neutrons drip from nuclei. For different values of _cr in the low-mass range (M 0.1 M) we calculate several series of configurations: we find the dependence of the stellar mass M on the central density _c for _cr = const, with 10⁹ g/cm³ _{cr drip} , and for each series we determine the parameters of the configuration for which the condition dM/d _c > 0 is violated. When the boundary density of the crust decreases to 10⁹ g/cm³, the minimum mass of a strange star decreases to M _min 10^-3 M, while the radius reaches 600 km.     

Structure of close binaries

Internal models have been obtained for uniformly rotating synchronous close binary systems using a modified double approximation scheme. We have considered primaries of 10M , 5M , and 2M with mass ratios of 0.0 to 1.0 in steps of 0.1, and some results are given for a 1M primary with a mass ratio of 1.0. A maximum luminosity reduction of 2.3% was found for a 10M primary with a mass ratio of 1.0 and 7.7% for a mass ratio of 0.0. The corresponding values for 5M are 2.0% and 7.0%, and for 2M they are 1.6% and 5.3%, respectively. These values were not found to be sensitive to small changes in composition. The maximum equatorial velocity varies from 399 km s^–1 for 2M to 567 km s^–1 for 10M when the mass ratio is zero, but these velocities decrease by 200–300 km s^–1 if the mass ratio is unity. The effect of gravity darkening on the apparent position of the primary in the theoretical H-R diagram was investigated. It was determined that an unresolved close binary of unit mass ratio can lie up to 0.9 magnitudes (depending on inclination) above the main sequence, whereas if the effects of distortion are ignored this number is at most 0.75 magnitudes. There seems to be some observational support for the larger value. Two models of the secondaries are given and their dimensions are compared with their critical Roche lobes.     

The product of the globular cluster collapse

In this paper we calculate the number of close binaries formed during the evolution process of a globular cluster core. The globular cluster core is assumed to contain a massive black hole at its center. We show that the central black hole can drive binaries formation in the core and the rate of binaries formation depends on the mass of the black hole at its center. When the massM of the black hole is between 10² M and 3×10³ M , there will be a few binaries formed. When the mass of the black hole is 4×10³ M M6×10³ M , the number of binary star formation will suddenly increase with a jump to the maximum value 58. When the mass of the black hole is 7×10³ M M9×10³ M , the number of binary star will immediately decrease. Whether cluster X-ray is produced mainly by the central black hole or by binaries in the core depends on the mass of the central black hole. Therefore, two cases arise: namely, black hole accretion domination and binaries radiation domination. We do think that we cannot exclude the possibility of the existence of a central black hole even when binary radiation characteristics have been observed in globular cluster X-ray sources.     

Supernova models with slow energy pumping and galactic supernova remnants

The study of supernova (SN) models with slow energy pumping is continued. At maximum luminosity the main characteristics of a SN are shown to be independent of the initial structure of the model (Table I, Figure 1). However, they depend on the massM _e of the envelope, and on the intensity of energy pumpingL , with an increase ofM _e leading qualitatively to the same changes in the SN parameters as a decrease inL (Table I, Figures 2 and 3). A simple relationship connecting the important SN parameters is obtained (Equation (6)). From the inflection of the color indexB-V curve, the possibility of deriving the characteristic time of energy pumping with intensityL 10⁴⁴ erg s^–1 is pointed out. The comparison of the extragalactic type I SN observations with the results of calculations leads to the estimate ofM _e 0.3–0.7M.An investigation of the galactic type I SN remnants is carried out (Table III). The estimate ofM _e 0.2–0.3M is obtained for the remnants of supernovae SN 1006, SN 1572, and SN 1604. It completely fits the results for the extragalactic type I SNs. The total initial mass of SN 1604 presupernova was shown to be at least about 7M .It was established that the Crab nebula resulted from the outburst of a peculiar SN. The unique properties of such SNs, including SN 1054, are due to the low intensity of energy pumping (L 10⁴² erg s^–1). The mass of the envelope of the Crab nebula is evaluated to beM _e 0.7M . SN 1054 was shown to have m _max ^v =–4 _m ^. 0 at maximum luminosity.     

The photometric solution of cc com by use of the

The contact binary system CC Com (=12^h09^m33^s.8, =+22°4339, (1950);V _max=11.31, (B-V)_max=1.24) is a W UMa-type system with the shortest known period. The photometric solution of CC Com is presented using the Wilson and Devinney method. The results show that the CC Com belongs to the late-type eclipsing binary with the spectral type K5V and K6V, low temperatureT ₁=4300 K,T ₂=4265 K, the mass ratioq=0.5873±0.0021, and the inclinationi=87°.719±1°.44. The best regions of the gravity darkening exponents , the bolomotric albedov, and the limb-darkening coefficients are tested. It is found that 0.1250.065, 0.1v0.5, =0.5 are better regions for CC Com. The third body ofl ₃ is not found to be significant. The results are combined with the spectroscopic results of Rucinski to provide an estimate of the absolute parameters.     

A Molecular Ring in the Liner Ngc 5218

High resolution OVRO CO 1–0 observations of the inner 30 in the LINER galaxy NGC 5218 reveal the presence of a double centrally peaked molecular concentration with extensions out to a radius of 12. The molecular mass detected is 2.4 × 10⁹ M and the gas surface density is high, 3000 M pc square in the inner 500 pc. The SFR is 2–3 M yr^–1 and the SFE is 13, which are low or moderate values for that gas surface density. We interpret the inner feature as a rotating molecular ring with a radius of 200 pc. We furthermore suggest that the LINER activity in NGC 5218 is not caused by an aging starburst, but by a buried AGN.     

The maximum mass of a neutron star

We consider the possibility that gravitational energy may play a local as well as global role in the behavior of matter in strong gravitational fields. A particular idealized equation, suggested as representing uniform energy density in general relativity, is examined, and its stability with respect to oscillatory and convective perturbations shown to be consistent with general relativistic hydrodynamics, subject to a new physical effect predicted for the behavior of fluids moving in strong fields. We calculate from this idealized equation the mass of a non-rotating neutron star, obtaining a maximum surface redshift ofz=2.48 and a maximum core mass of 9.79 ₁₄ ^–1/2 M. This compares withz=2.00 and 11.4 ₁₄ ^–1/2 M for a Schwarzschild star (=const.) and 6.8 ₁₄ ^–1/2 M for a causal star (dP/d1).     

Numerical simulations of pulsationally unstable accretion disks around supermassive black holes

The innermost region of slim accretion disks with standard viscosity is unstable against axisymmetric radial inertial acoustic perturbations under certain conditions. Numerical simulations are performed in order to demonstrate behaviors of such unstable disks. It is shown that oscillations with the period of 10^–3 (M _BH/M ) s can be excited near the inner edge of the disks, whereM _BH is the mass of the central object. This kind of unstable disks is a possible origin of the periodic X-ray time variabilities with period of 10⁴s observed in a Seyfert galaxy NGC 6814.     

High velocity neutron stars and γ-ray bursts

The observations of the BATSE instrument on the Compton Gamma-Ray Observatory show that the spatial distribution of -ray burst sources is isotropic but radially non-uniform. As is well known, the spectral features, the time histories and the X-ray tails present in some -ray bursts suggest that they may arise from galactic neutron stars. But, low velocity neutron stars born in the Galactic disk would concentrate toward the galactic plane and center, and could not fit the BATSE results. However, the high velocity neutron stars with velocity 1000 km s^–1 may escape from the Galactic gravitational field and form a nearly isotropic distribution. Here we calculate the three statistical values of V/V _max, sin² b and cos as functions of the intensitiesC _max/C _min and find that they could be fitted by the distribution of high velocity neutron stars under the assumption that the high velocity neutron stars should turn on as -ray burst sources only after some time (perhaps after they have ceased to be radio pulsars). Our calculation shows that the statistical value of cos is more sensitive than sin² b to the angular distribution of high velocity neutron stars, i.e. the deviation of cos from 0 is more readily detected than the deviation of sin² b from 1/3, so we expect that with the increasing sensitivity of instrument and the more exact value of cos , it is possible to determine whether this high velocity neutron star model is correct. Some results are discussed in the text.     

Observations and analysis of CF Tuc

RecentUBV photometry of the RS CVn binary CF Tuc is discussed and analysed. If we combine the results with previously published spectroscopy we find radii of 1.63R for the hotter (6000 K) and 3.11R for the cooler (4500 K) component; both stars having a mass of about 1.3M . The distance to the system is put at 86±15 pc.Though the photometric data is incomplete in the coverage of some regions out of the minima, there is no significant evidence of the wave-type distortions — a known hallmark of RS CVn stars — and the data can be modeled by a standard eclipsing binary system in which the statistical test of goodness-of-fit (²) produces quite acceptable values for reasonable estimates of observational accuracy (0.01 mag). We, therefore, have no need to postulate any additional photometric complications, and feel entitled to some confidence in the reliability of the derived parameter set.     

Ionization feedback mechanism in the recombination era of the Universe

Within the cosmological standard models of the Universe, we inquire the 2-fluid radiation hydrodynamics during and before the recombination era. If we neglect all nonlinearities with exception of those contained in the coupling term between the two fluids via the degree of ionization, there exists a strong feedback mechanism on the instable modes which prevents them from growing if their relative amplitudes of the density contrast have values in the order of 10^–1–10^–2. The non-linear equations are numerically solved by adiabatic elimination technique used usually in self-organization problems. The effect depends very on the redshift z and become maximum atz1350. It depends also on the masses involved for the rangeM>10¹¹ M . The lowest limits in the amplitudes (10^–2) are imposed on the largest masses (10¹⁷ M ). In the range 10⁶M/M 10¹¹, the effect is independent of the mass.     

Evolution of binaries with ultra-short periods: Systematic study

A detailed investigation of the evolution of low-mass binaries is performed for the case when the secondary fills its Roche lobe at the stage of core hydrogen exhaustion. The obtained results are compared with observational data for ultra-short periodic X-ray systems MXB 1820-30 and MXB 1916-05. In the frame of the proposed evolutionary scenario it is possible to obtain for MXB 1820-30 its periodP=11.4 min twice (see Figure 2). In the first case the parameters of the system are:M ₂ 0.13–0.15M ,X0.05–0.13, |P/P| (3.6–6.2) } 10^–7 yr^–1, M₂ (4.1–9.6) } 10^–9 M yr^–1, for the second:M ₂ 0.08–0.09M ,X= 0, |P/P| (1.3–1.5) } 10^–7 yr^–1, M₂ (1.4–1.8) } 10^–8 M yr^–1. It is suggested that MXB 1916-05 is the progenitor of the system MXB 1820-30 (M ₂ = 0.1M,X 0.221,M ₂ 1.8 × 10^–10 M yr^–1).     

Effect of drift-resonance broadening on radial diffusion in the magnetosphere

In the quasilinear theory of magnetospheric radial diffusion caused by fluctuating electrostatic (E) or magnetic (B) fields, the diffusion coefficientD _LLis proportional to the spectral density of E or B at the particle drift frequency ₃/2. Since ₃ varies withL at fixedM andJ (adiabatic invariants), the drift resonance =₃ can be maintained only transiently, and therefore is not perfectly sharp. Its bandwidth ^* is approximately (16D _LL /L ²₃)^1/3₃. In magnetospheric radial diffusion caused mainly by electrostatic fluctuations, the value of ^*₃ typically exceeds 0.4 for particle energiesE40 keV. However, the numerical value ofD _LLis correctly given (within 1% in all cases) by quasilinear theory because the spectrum of E is rather flat at resonance frequencies for which the bandwidth is an appreciable fraction of ₃. (Numerical conclusions are based on a quasilinear model forD _LLused successfully by Cornwall in 1972.)     

The properties of the strong static field of a collapsar in gravidynamics

In the bounds of the totally nonmetric model of gravitational interaction theory (gravidynamics) the strong field of a compact object (a collapsar) — an analogue to the black hole in general relativity — is investigated. In the case of utmost strong (for gravidynamics) collapsar, field a region filled, by matter (a bag) must have the radius equal tor _*=GM/c ² 10 km at the total collapsar massM7M . Only half of the collapsar mass is contained in the bag, the other one of its total energy (Mc ² ) is distributed in the space surrounding the bag in the form of a coat, i.e., in the form of continuous medium (a relativistic gas) of virtual gravitons. The object must have the surface (the bag surface) with absolutely definite physical properties. The potential of such a surface is finite (₊=-c ²/2) and the particle mass finding itself in a bound state on the bag surface is two times less than the mass of the same particle in a totally free state. The bag surface can perform periodic oscillations (pulsations) with the periodGM/c ² 3×10^–5 s. An energy density inside the bag with the utmost strong gravitational field or with an utmost dense coat shrouding the bag is determined by gravitation theory constants only and depends on the distance to the bag centerr in the following way: (r)=(c ⁵ /8G)r ^–2. The bag matter in the case is most probably in the state of quark-gluon plasma.     

Possible evidence for a massive black hole in a quasar with double redshift systems

With the aid of a simple black hole model of quasars we have found that the majority of the distinguishable emission lines in the spectrum of the quasar 1604+179 can be assigned to two redshift systems,z _r =3.712 andz _b =2.701. The appearance of double emission redshifts means that this quasar might be a massive black hole (of mass 10⁸ M M10¹¹ M ) with a ring-like emission line region (of radius 1 light-day r ₀1 light-year) in its accretion disk.     

Grain formation in the expanding gas flow around cool luminous stars

We studied grain formation process and flow structure around cool luminous mass-loss stars. The nucleation and growth theory of Yamamoto and Hasegawa was extended to the case of expanding gas flow.The envelope was assumed to be steady, spherically symmetric, in thermal and radiative equilibrium, optically thin, and driven by radiation pressure on grains. For oxygen rich stars, Mg-silicate was found to be the first condensate which can drive the gas effectively. The following stellar parameters were chosen; stellar massM _*=1M , effective temperatureT _*=3000K, stellar luminosityL _* from 7.5×10³ to 2.0×10⁴ L , and mass-loss rate |M| from 1.0×10^–6 to 1.0×10^–4 M yr^–1.Main results of calculations are as follows; (1) grain condensation temperatureT _c9801080 K; (2) total gas pressure at the condensation pointP _t6×10^–116×10^–9 atm; (3) scale parameterA _c10³6×10⁴; and (4) final grain sizer _f=400Å1m. For the smaller |M| or the largerL _*, these values are the smaller. We recognized two types of flow solutions (1) Dust driven flow for large |M|, which reaches the sonic point near the condensation point; and (2) Modified Parker flow for small |M| for which grain sizer _f is almost independent of |M|.A comparison with observational results ofL _* and gas terminal velocityV suggests that Mg-silicate grains are of submicron size, which are effective for interstellar extinction in visible and infrared. Fe-grains condense in the rarefied outflow with a size probably smaller than 100Å, which may contribute for interstellar ultraviolet extinction. The envelope has three-layer structure inner dense region with small outflow velocity, grain formation layer and outer rarefied region with fast outflow velocity.No flow solutions exist forM _* greater than a critical stellar massM _*cr for a given stellar luminosityL _* and mass-loss rate |M|.For example, critical stellar massM _*cr=1.8M forL _*=10⁴ L ,T _*=3000 K, and |M|=10^-5 M yr^-1.     

Possible mass limits for quantum double galaxies

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.     

Implications of a strongly peaked polar magnetic field

Using the flux-transport equation in the absence of sources, we study the relation between a highly peaked polar magnetic field and the poleward meridional flow that concentrates it. If the maximum flow speed _m greatly exceeds the effective diffusion speed /R, then the field has a quasi-equilibrium configuration in which the poleward convection of flux via meridional flow approximately balances the equatorward spreading via supergranular diffusion. In this case, the flow speed () and the magnetic field B() are related by the steady-state approximation () (/R)B()/B() over a wide range of colatitudes from the poles to midlatitudes. In particular, a general flow profile of the form sin ^p cos ^q which peaks near the equator (q p) will correspond to a cos ⁿ magnetic field at high latitudes only if p = 1 and _m = n /R. Recent measurements of n 8 and 600 km² s^–1 would then give _m 7 m s^–1.