Our galaxy — A former seyfert?

A re-interpretation is offered for both the galactic center lobe and the high-velocity clouds in the galactic halo: the galactic center lobe is a 2-sided chimney for relativistic pair plasma emerging from the center of the Milky Way (=Sag A^*) and streaming as 2 jets through the halo. The channel walls of the flow serve as cold traps for the galactic fountain whenceHi clouds rain back into the disk.     

The galactic diffuse component of soft X-rays and its source function

A new model for the source distribution of galactic soft X-ray (B and C band) emission is presented. From the mean dependence of count rates on galactic latitudeb (i.e., the brightness distribution), we derive the soft X-ray source functionQ as function of the optical depth by solving the equation of radiative transfer with the aid of a Laplace transform. Contrary to older Heaviside step models,Q is found to increase strongly, but not abruptly, in the range 1.5<<2.5, indicating a noticeable emission of X-rays from beyond theHi scale height. Using standard X-ray absorption cross-sections for the interstellar medium, we find that the B band X-ray emission coefficient is non-zero within theHi disk and has a maximum at az-value slightly above the Hi scale height. In the C band, the emission coefficient slightly decreases with increasingz, at least up to theHi scale height. A non-zero source function near the galactic plane implies that the interstellar medium (ISM) within theHi scale height is not only an absorbing layer but is mixed with X-ray emitting regions. The so-called local hot bubble is adopted as one of these regions. The maximum of the B band emission coefficient, together with the sharp increase ofQ, is strong evidence for the existence of a galactic soft X-ray halo, and, moreover, give rise to the assumption of a general intergalactic X-ray background. The effective absorption cross-sections given in the literature, based on an (pure) exponential dependence in the negative correlation between count rates andHi column densities, were biased to be too small, in particular in the B band. In replacing the Heaviside step (in the ISM) by a smoothed transition region, these inconsistencies become spurious.     

Stockert's chimney — A galactic fountain

A new type of galactic outflow phenomenon has been discovered and published under the name of thermal spur by Mülleret al. (1987). It is argued that this outflow consists of relativistic pair plasma with an admixture of partially ionized hydrogen and cosmic rays, escaping from a large Hii region. This chimney serves as a substantial leak for the cosmic rays, i.e., may be an essential part of the galactic foundtain.     

Hα Doppler brightening and Lyman-α Doppler dimming in moving Hα prominences

We consider the effect that coherent motion has on the observed brightness of moving clouds above the photosphere. We find that steady state clouds (constant N _e and T _e ) that are moving perpendicular to the line of sight will appear brighter in H for speeds between 8 and 100 km/sec and dimmer for speeds greater than 135 km/sec. The brightening and dimming are due to apparent Doppler shifts of the respective H absorption and the Lyman- emission profiles seen by the absorption profile of the moving cloud.We apply this analysis, along with optical depth and geometrical considerations, to the observed brightness variations of the 1 March 1969 limb eruptive prominence. We find that all of the observed brightening and dimming can be explained by the motions, and that no significant change in the prominence N _e or T _e was necessary during the observed H event. This conclusion is significant in interpreting an X-ray burst that began as the prominence velocity increased abruptly at the time of maximum H intensity. The thermal X-ray peak occurred 150 sec later when the prominence had become faint again. There was no associated flare that was visible in H. We discuss the relative brightness of H and D ₃ in a specific moving prominence knot.We note that the observed range of limb speeds (30–150 km/sec) may be due to the combined H Doppler brightening and Lyman- dimming effects. We also discuss generally the H brightness of disk surges (bright and dark) and flares, and sprays and puffs that occur at or near the limb.Now at the Dept. of Physics and Astrophysics, University of Colorado, and High Altitude Observatory (NCAR) Boulder, Colo., U.S.A.     

Plasma acceleration by radiation in X-ray pulsars

Charged particle acceleration is considered by a radiation flux from a star or hot spot in X-ray pulsars. It is shown that for any distance from the star there exists the upper velocity limit up to which a particle can be accelerated by radiation. This critical velocity does not depend on the luminosity of the spot. Near the hot spot surface the critical velocityv0.65c. These results are applied to plasma acceleration inX-ray pulsars. The mechanism is advanced, of -ray generation in the course of plasma accretion, onto a neutron star. It is shown that in the presence of a large magnetic field and high luminosity of the spot the relativistic electron-position avalanche may appear. The optical depth of the electron-positron cloud achieves the value of order one. The X-ray quanta emitted by the spot are scattered by relativistic (2.6) electron-positron pairs and are transformed into -radiation. Hard quanta with energy 1 MeV leave the generation region in the narrow cone 0.25.     

On the stability of small quasiperiodic motions in the hamiltonian systems

Orbital stability of quasiperiodic motions in the many dimensional autonomic hamiltonian systems is considered. Studied motions are supposed to be not far from equilibrium, the number of their basic frequencies may be not equal to the number of degrees of freedom, and the procedure of their construction is supposed to be converged. The stability problem is solved in the strict nonlinear mode.Obtained results are used in the stability investigation of small plane motions near the lagrangian solutions of the three-dimensional circular restricted three-body problem. The values of parameters for which the plane motions are unstable have been found.

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The structure of the broad line region in Fairall 9

We find that the profile changes observed for the UV emission lines L,Civ 1549, and MgIII 2798, in the Seyfert 1 galaxy Fairall 9 occur mainly near the line centre for L andCiv and in the wings for MgIII. These results indicate that the broad line region (BLR) has a complex structure, possibly with non-spherical components.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

The observed limb effect in Fraunhofer lines,I

The absolute limb effect is presented for Fei lines 3767 and 3969; for five Tii lines of multiplet 42 near 4535 and one Tiii line at 4534; two lines of Mgi, 4571 and 5172; two lines of Baii at 5854 and 6497. The scattered light of the McMath solar telescope is illustrated by several figures but not applied to the limb-effect observations. It is suggested that the supergravity shift at the limb is the result of scattering of the atoms in anisotropic velocity field.Operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.     

The virial-based solution for the velocity of gaseous sphere gravitational contraction

It is found that the relationship between the potential energy and the moment of the inertia independent of the radial mass distribution obtained earlier for the sphere also holds in the case of the ellipsoidal mass distribution for the ellipsoid of rotation.The possibility of application of the energy virial relations for solution of the evolutionary problems of the gravitating gaseous sphere, with the help of the relationship found earlier, is demonstrated. The physical conditions on the gaseous sphere boundary are introduced. The existence of two branches of evolution, the proton one and the electron one, is established. The problem of the gravitational contraction velocity during sphere evolution is solved. The relationship between the boundary temperature and the gaseous sphere radius as well as between the luminosity and the body mass is obtained. Some limiting relations for the final stage of the gaseous sphere evolution are found.

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The stability of supermassive stars in the Parametrized Post-Newtonian framework

The binding energy and stability of supermassive stars (SMS's) is examined in the framework of the Parametrized Post-Newtonian (PPN) formalism of Will and Nordvedt. The PPN formalism encompasses the post-Newtonian limit of virtually every theory of gravity, differentiating between theories by means of nine PPN parameters. A general expression is derived for the energy integral in the PPN framework, and it is found that only in those theories in which the parameters ₁=₂=₃=₄=₃=0 will the energy be conserved. In all such theories, a SMS of radius less than a critical radius will be unstable against adiabatic radial perturbations. Present experimental limits on the PPN parameters and do not exclude the possibility of the existence of stable, non-rotating, hydrogen-burning SMS's of masses an order of magnitude larger than the upper limit for the mass of such stars predicted in general relativity.     

Neutral hydrogen filaments at high galactic latitudes

Small angular scale twists in Hi filaments identified at high galactic latitudes are associated with the location of enhanced emission features (EEFs), structures that have traditionally been referred to as clouds. It is shown that in these directions the column density of gas is enhanced through geometrical effects because the line-of-sight intersects a greater pathlength when viewing along a segment of filament axis (flux tube) than when the tline-of-sight is more normal to the filament axis. By interpreting the EEFs as isolated entities (clouds) we derive an incorrect impression as regards the properties of interstellar Hi. For example, EEFs are typically a factor of five to ten times deeper than they are wide and, hence, the derived properties of Hi structures that have traditionally been taken to be as deep as they are wide are incorrect. This study leads to questions about the way observations of 21 cm, molecular, and 100 emission are currently being interpreted. It is concluded that much of what is observed to be cloud structure in the interstellar medium (except in regions directly associated with star formation) is telling us about geometry of filaments and not about the physics of clouds, The very notion of an interstellar cloud may have outlived its usefulness and previous work that has attempted to account for these structures in terms of gravitational stability or pressure equilibrium has to be reconsidered in the light of the existence of complex patterns of filamentary structure, not only in the Hi distribution but also of interstellar cirrus defined by 100 emission.     

Rapid simultaneous observations of Feii and Balmer emission lines of X Oph

Sudden brightening of FeII and Balmer (H and H) lines of X Oph was observed on 28–29 May, 1986. Equivalent width of FeII and H lines increased by a factor of two and that for H line by a factor of four, during the brigtening phase of the star. This brightening phenomena has been explained in the framework of Coronal Radiative Instability.     

Fine structure in the inner corona observed at the 1970 eclipse

On the slit spectrogram obtained at the 1970 eclipse in Mexico, the intensities of four coronal lines (Nixiii 5116, Fexiv 5303, Fex 6374, and Nixv 6702) and the continuum were measured as a function of distance along the slit. It is found that there exist a lot of fine fluctuations both in the lines and in the continuum intensities superposed on a large scale formation. The correspondence of such fluctuations between the continuum and the lines is good, with the exception of the line 6374 which shows a peculiar fluctuation. It is shown that the intensities of the three lines 5116, 5303, and 6702 seem to be proportional to the square of the continuum intensity while the 6374 line intensity may be proportional to the fourth power or more.     

Narrow band CCD imagery of southern galaxies in strong lines and continua: NGC 613

CCD narrow band imagery of the southern barred spiral NGC 613 has been obtained in the light of H, H, [Oiii] 5007 Å, [Oii] (3726+29) Å and continua at 3765, 5230, and 6500 Å. Absolute fluxes have been obtained for the lines H and [Oiii] 5007 Å and continua at 5230 and 6500 Å. Distribution of ages, monochromatic colour vs absolute brightness and [Oiii]/H are discussed.     

Interaction between the interstellar medium and solar wind plasma

The interaction processes governing the penetration of the interstellar gas into the solar neighbourhood are re-examined — as well as photo-ionization and charge-exchange processes, proton elastic collisions and electron ionizations help reduce the nearby gas densities. The total destruction rate varies little during the solar cycle, by perhaps 10%. Particle heating, particularly via the elastic collisions, determines the gas characteristics in the gravitationally focussed tail—enhanced H-density is prevented, while the He-tail is effectively hotter than 10³ K.Termination of the solar wind is rediscussed in the light of both electron heating and the stronger gas/plasma interaction. The spiral interplanetary field is taken to break up and the subsonic plasma flow to be controlled by the pressure of slowly cooling electrons. The terminating collisionless shock is then, if it exists at all, very weak (M ₁<1.4), subcritical, and energetically unimportant. Cosmic rays are little affected by this sonic transition, but at least the electron component should be modulated by plasma turbulence throughout the ionizing flow.

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Structure and physics of solar faculae

Taking into account the effect of roughness (or local departures from sphericity) of the emitting layers in the chromosphere-corona transition zone (CCT) allows one to determine the optical depths of layers responsible for resolved structures in Cii, Ciii, Oiv, and Ovi lines. The result, at the top of the irregularities, is of the order of respectively ₁ 3.5,2.0, 1.6,0.5, and for the bottom of these irregularities, ₂ = 0.7, 0.4, 0.3, 0.25. The characteristic angle of these irregularities is, respectively, of the order of 35 °, 33 °, 35 °, and 41 °. For unresolved structures of Civ and Ovi (already analyzed in the spherical symmetry hypothesis in Paper III), one finds ₁ 0.6; 0.9 and ₂ 0.12; 0.2 in the case of quiet areas; in the case of active areas, the range is broader for Civ and Ovi, from 1.0 to 1.7 for ₁ and from 0.2 to 0.9 for ₂. The values obtained from Ovi are in reasonable agreement with each other for resolved and unresolved structures. And the obtained values of ₁ and ₂ correspond not too badly with the determinations made in Paper III, by methods not exceedingly influenced by the spherical symmetry hypothesis.     

About the stability of the libration points of a rotating triaxial ellipsoid in a degenerate case

The problem of stability of the equilibrium points in the problem of motion of a mass point in the neighbourhood of a rotating triaxial ellipsoid in a degenerate case (the Gaussian of the Hamiltonian is equal to zero) is investigated.It is proved that the equilibrium points in the degenerate case are stable in the strict sence.

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Résumé On étudie le problème de la stabilité des positions d'équilibre relatif dans le problème du mouvement du point matériel au voisinage de l'ellipsoid à trois axes tournant dans un cas dégénéré (le gaussian du Hamiltonian égal zéro).On a démontré que des positions d'équilibre relatif dans le dégénéré sont stables dans le sens rigoureux.

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Narrow-band photometry of Wolf-Rayet stars and planetary nebulae

We present observational data in the (16)(9)(25)-photometric system for 11 Wolf-Rayet stars and 7 planetary nebulae. The results show anomalous (16)(9)-indices for these emission objects. Six W-R stars show possible variations in the strength of the HeII line at 6560 Å, perhaps none in the strength of the HeI line at 10830 Å. In spite of these misconstrued (16) and (9)-indices, most WC stars are separated from WN stars in the (16)(9)-array; and PN, in this diagram lie far apart from all kind of stellar objects. The results, yielded by the (25)-index, indicate that the HeI and HeII lines at 10830 Å and 10124 Å, respectively, are probably well suited for photometric examination in W-R stars, PN and other peculiar objects.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

Hubble sequence,angular momenta and time-scales of the early evolution of galaxies

The empirical evidence for a connection between type and relative angular momentum of galaxies is reviewed and some constraints for the theoretical explanation are discussed.

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Second order adiabatic invariants associated with the two-body problem with slowly varying mass

An adiabatic invariant is characterized by the property that its derivative is small and oscillatory. Therefore, assuming that such a quantity is constant does not lead to a cumulative error as t. In this paper, using action and angle variables, adiabatic invariants to 0(1) and 0() are found for the two-body problem with a slowly varying gravitational constant.