The conversion from neutron stars to strange stars and its implications

The conversion from neutron stars with different equation of states (EOSs) for neutron matter into strange stars with different EOSs for strange quark matter has been studied in a general relativistic numerical calculation in this paper. For hot neutron stars, their conversion may lead to great variations in their rotation periods, of which the magnitude would be greatly dependent upon the EOS for neutron matter, and of which the timescale would be greatly determined by the EOS for strange matter. This phenomenon appears as giant glitches, which might provide a probe of EOSs for both neutron matter and strange matter. But for cold neutron stars, their conversion may result in a population of gamma-ray bursts.     

GalevNB: a conversion from N-body simulations to observations

We present GalevNB(Galev for N-body simulations), a utility that converts fundamental stellar properties of N-body simulations into observational properties using the GALEV(GAlaxy EVolutionary synthesis models) package, and allowing direct comparisons between observations and N-body simulations.It works by converting fundamental stellar properties, such as stellar mass, temperature, luminosity and metallicity into observational magnitudes for a variety of filters used by mainstream instruments/telescopes,such as HST, ESO, SDSS, 2MASS, etc., and into spectra that span the range from far-UV(90 ) to near-IR(160 μm). As an application, we use GalevNB to investigate the secular evolution of the spectral energy distribution(SED) and color magnitude diagram(CMD) of a simulated star cluster over a few hundred million years. With the results given by GalevNB we discover a UV-excess in the SED of the cluster over the whole simulation time. We also identify four candidates that contribute to the FUV peak: core helium burning stars, second asymptotic giant branch(AGB) stars, white dwarfs and naked helium stars.     

Analytical expressions of the Earth's position and velocity for the calculation of apparent positions

In order to calculate the apparent places of stars, the barycentric and heliocentric positions of the Earth and the barycentric velocity of the Earth are required. It is shown that several tens of trigonometric terms for their expressions are sufficient for analyses of optical observations which have an observational accuracy of the order of 0.001. We also give the analytical expressions of the position and velocity of the Earth with higher precision so that we can use them in the analyses of precise astrometry such as VLBI observations.     

On the depth dependence of the solar rotation velocity determined from fraunhofer lines

From 63 mostly unblended Fraunhofer lines measured along the solar east-west diameter the rotation velocity has been determined. The mean value is 1986 km s^#X2212;1. The velocity decreases with the optical depth in the photosphere. Over a range of 700 km the difference of the velocities is 41 m s^#X2212;1 for the Holweger-Müller atmosphere or 34 m s^#X2212;1 for the Harvard Smithsonian reference atmosphere.     

Radiant point,trajectory and velocity from single photographic or TV observation

The radiant point can be decided by using assumption that a meteor's velocity is constant by only one photograph with rotation shutter or one TV camera. Trajectory and initial velocity can be decided by using additional assumption beginning with the height of a meteor. In this method, the radiant point can be computed accurately when trajectory length is long enough which can be regarded constant velocity and measurement's error is small.     

On a possible control mechanism for solar wind outflow velocity from coronal holes

In this paper we give an explanation for a control mechanism for velocityV of solar wind (SW) streams for coronal holes (CHs) based on the idea suggested by Rudenko and Fainshtein (1993). In accordance with that idea, the difference of values ofV in high-speed SW streams from different CHs is due to the spread in magnitude of magnetic fieldB _a in the region of acceleration of such streams near the Sun. In this case, with increasing magnitude ofB _a, there is an increase in velocity of the high-speed stream.Through calculations of the coronal magnetic field (potential-field approximation) it is shown that on the source surface the magnetic field B _s, averaged over the cross-section of the magnetic tube from a CH, can vary for different tubes over a wide range and correlates quite well with the area of this tube's base as well as depending on the radial component of the magnetic field at the base of the tube on the source surface B _or.It is found that the value of superradial divergence of the magnetic tube from a CH depends not only on the area of its base (as shown in prior work) but also on B _or. A positive correlation at the Earth's orbit between velocityV of the high-speed SW and the radial component of the magnetic field in the region of this stream is detected, which agrees indirectly with theV-control mechanism under discussion.     

From rotations and inclinations to zero configurational velocity surfaces,II. The best possible configurational velocity surfaces

The best possible zero configurational velocity surfaces for the generalN-body problem in three space are derived. The basic construction of these surfaces is described in detail for the three body problem and for other flat configurations. The construction for nonflat configurations is outlined.This paper is dedicated to the memory of Harry Pollard: my mentor, my collaborator, and my good friend.     

On the inclination and the axial velocity of spicules

This paper studies two properties of chromospheric spicules: their angular distribution and the plasma velocity along their axes. To investigate the first property, we measured the apparent tilt of spicules at the limb, and then computed their actual distribution in space. This was achieved by solving first kind Fredholm or Volterra integral equations by various methods. The distribution of the axial velocity of the spicule plasma was studied on the basis of two types of observations: (1) the height variation of the spicules as a function of time and (2) the Doppler shift of the spectral lines. The resulting velocity distributions, using the experimental data of these two sets of observations, are quite different. The average velocity based on the Doppler shift measurements ( 40 km s^–1) is greater than that based on height variation of spicules ( 20 km s^–1). This is due to the ionization of the material as it penetrates the corona.     

On the stability of helical velocity and magnetic fields

In this paper we study the stability of an infinitely conducting, incompressible, inviscid infinite cylinder with non-parallel helical velocity and magnetic field. It is shown that the system is stable if the energy in the -component of the velocity field is larger than that in the -component of the magnetic field.     

On the determination of the photospheric velocity distribution from profiles of weak Fraunhofer lines

The steady-state vertical-velocity response of an isothermal atmosphere to pressure fluctuations of arbitrary period and horizontal wavelength at its base is derived in the approximation of dissipationless polytropic motion in the atmosphere. It is pointed out that, since only upward modes can be excited in an isothermal atmosphere perturbed from below, the infinite response found by Worrall (1972) at the critical frequency _g does not occur. The correct behavior of the response is presented in some detail.Comparison of the response of the model, for the case of isothermal osculations, with observed features of the photospheric oscillations indicates that, in addition to the evanescent photospheric oscillations which occur at the compression-wave propagation cut-off frequencies and which have horizontal wavelengths 3000 km, in the lower photosphere there are also smaller-scale evanescent oscillations which have horizontal wavelengths 1000 km, periods ranging from 200 to 400 s, amplitudes comparable to that of the larger-scale oscillations, and in which the phase of the vertical velocity oscillation leads the phase of the pressure oscillation.     

On volatilization in vacuum of the elements from the planet surface soil melts

Endogeneous and exogeneous events resulting in the appearance of the large volumes of melted substance on the lunar surface should be accompanied by volatilization of some elements from melts in vacuum [1]. However, it is not clear up to now whether volatilization on the Moon has indeed occurred and how the lower (in comparison with the Earth) content of some elements (Na, K and others) in lunar soil can be explained. There are contradictory opinions on these problems in publications (O'Hara, Ringwood and others) [2]. The numerous laboratory investigations of the similar processes are insufficient [3–15; 36] for interpretation of the results for the lack of an adequate physical model and the theory of these processes and also due to the narrow range of the parameters used (T, p, τ) and the experimental regimes. In the present paper a physical model is developed, which is based on experimental data; together with a theory of the process of volatilization of the volatile components of rock melts in vacuum, taking into account an adsorption of the residual atmosphere gases; all these allow us to interpret such processes successfully. As a result, some preliminary conclusions have been drawn about such phenomena on the Moon and their laboratory simulation.     

On the dispersal and mixing of heavy elements

Two different paths can be followed by the ejecta of correlated supernovae as a result of the size of the starburst, and the mass and density of the parent galaxy. In the case of the nuclei of massive ellipticals and bulges of spirals, as well as for nuclear starbursts in spiral galaxies, it is quite clear that most of the metals produced by massive bursts of star formation are dumped onto the intergalactic medium. This happens once the resultant superbubble reaches the outskirts of a galaxy, causing a superwind. The product of less massive starbursts is, however, retained by galaxies, even in the case of blue compact dwarfs, leading, after 100 Myr, to an enhanced abundance of the ISM. Here, I review the steps required for a rapid and a slow mixing of heavy elements with the ISM and show under which conditions they apply.     

Radial,transverse and normal satellite position perturbations due to the geopotential

Perturbations in the position of a satellite due to the Earth's gravitational effects are presented. The perturbations are given in the radial, transverse (or alongtrack) and normal (or cross-track) components. The solution is obtained by projecting the Kepler element perturbations obtained by Kaula [Kaula, 1966] into each of the three components. The resulting perturbations are presented in a form analogous to the form of Kaula's solution which facilitates implementation and interpretation.     

On mode conversion and wave reflection in magnetic Ap stars

We investigate the effect of a strong large-scale magnetic field on the reflection of high-frequency acoustic modes in rapidly oscillating Ap stars. To that end, we consider a toy model composed of an isothermal atmosphere matched on to a polytropic interior and determine the numerical solution to the set of ideal magnetohydrodynamic equations in a local plane-parallel approximation with constant gravity. Using the numerical solution in combination with approximate analytical solutions that are valid in the limits where the magnetic and acoustic components are decoupled, we calculate the relative fraction of energy flux that is carried away in each oscillation cycle by running acoustic waves in the atmosphere and running magnetic waves in the interior. For oscillation frequencies above the acoustic cut-off, we show that most energy losses associated with the presence of running waves occur in regions where the magnetic field is close to vertical. Moreover, by considering the depth dependence of the energy associated with the magnetic component of the wave in the atmosphere we show that a fraction of the wave energy is kept in the oscillation every cycle. For frequencies above the acoustic cut-off frequency, such energy is concentrated in regions where the magnetic field is significantly inclined in relation to the local vertical. Even though our calculations were aimed at studying oscillations with frequencies above the acoustic cut-off frequency, based on our results we discuss what results may be expected for oscillations of lower frequency.     

On the velocity distribution of the minor planets and stars

The velocity distribution of the minor planets is studied in comparison with that of the stars in the neighbourhood of the Sun. The phase configuration at a given instant has been obtained and the distribution has been studied for different ecliptic sectors. The velocity distribution of the minor planets is similar to that of the stars and differs little form the trivariate normal distribution. The vertex presents a deviation from the direction of the Sun which is positive or negative for different sectors. This vertex deviation is a consequence of the orbit orientations. The relaxation time, deduced from the encounters between the minor planets, is of the order of 10¹⁴ to 10¹⁶ yr.     

On the relationship between magnetic fields and supergranule velocity fields

We studied the size, correlation lifetime and horizontal velocity amplitude of supergranules in regions with different magnetic activity. We found that the supergranule velocity cells have similar scale, correlation lifetime and horizontal velocity amplitude in the unipolar enhanced magnetic network regions and in the mixed-polarity quiet Sun. However, the correlation lifetime of magnetic structure is much longer in the enhanced network. We investigated the velocity pattern of moving magnetic features (MMF) surrounding a decaying sunspot. The velocity of MMFs is consistent with the outflow surrounding the sunspot as measured by Dopplergrams. The velocity cell surrounding the sunspot has a much larger velocity amplitude and a longer lifetime than regular supergranule cells. We found that ephemeral regions (ER) have a slight tendency to emerge at or near boundaries of supergranules. Almost all the magnetic flux disappears at the supergranule boundaries. In most cases, two poles of cancelling features with opposite magnetic polarities approach along the boundaries of supergranules.     

On the velocity of jets powering hot spots similar to those in Cygnus A

Hot spots similar to those in the radio galaxy Cygnus A can be explained by the strong shock produced by a supersonic but classical jet \(\left( {u_{jet}< c/\sqrt 3 } \right)\) . The high integrated radio luminosity (L?2×10⁴⁴ erg s^?1) and the strength of mean magnetic field (B?2×10^?4 G) suggest the hot spots are the downstream flow of a very strong shock which generates the ultrarelativistic electrons of energy ?≥20 MeV. The fully-developed subsonic turbulence amplifies the magnetic field of the jet up to 1.6×10^?4 G by the dynamo effect. If we assume that the post-shock pressure is dominated by relativistic particles, the ratio between the magnetic energy density to the energy density in relativistic particles is found to be ?2×10^?2, showing that the generally accepted hypothesis of equipartition is not valid for hot spots. The current analysis allows the determination of physical parameters inside hot spots. It is found that:

1. The velocity of the upstream flow in the frame of reference of the shock isu ₁?0.2c. Radio observations indicate that the velocity of separation of hot spots isu _sep?0.05c, so that the velocity of the jet isu _jet=u ₁+u _sep?0.25c.
2. The density of the thermal electrons inside the hot spot isn ₂?5×10^?3 e ^? cm^?3 and the mass ejected per year to power the hot spot is ?4M ₀yr^?1.
3. The relativistic electron density is less than 20% of the thermal electron density inside the hot spot and the spectrum is a power law which continues to energies as low as 30 MeV.
4. The energy density of relativistic protons is lower than the energy density of relativistic electrons unlike the situation for cosmic rays in the Galaxy.