Cerenkov line emission: The Lα/Hβ, Hα/Hβ, Pα/Hα intensity ratios of quasars

We use the Cerenkov line emission mechanism to give a new explanation of the observed intensity ratios, particularly the L/H ratio, of the emission lines of quasars. We give equations that restrict the choice of the parameter values. The parameters are the characteristic energy of the relativistic electrons, the number density of neutral hydrogen and its relative level populations. With reasonable choice of the parmaeters, we can obtain calculated L/H, H/H, P/H ratios in agreement with observed values. Our estimate for the gas density in the broad line region of quasars is 10¹⁵ cm^–3, very different from previous estimates. Unlike previous theories, such a high density causes no difficulties with the Cerenkov line emission.     

The spectral indices in the optical continuum of the QSOs,BL Lacertae objects and the nuclei of Seyfert,N and normal galaxies

The hypothesis that the optical continua of QSOs, BL Lac objects and the nuclei of Seyfert, N and normal galaxies arise due to incoherent synchrotron radiation from electrons and consequently the flux of radiation in the optical continua of these objects is given by the power law:F(v)v is examined. Following Kinman, spectral indices _B–V and _U–B in(B-V) and(U-B) colours as well as their average and difference have been defined and calculated for samples of 227 QSOs, 32 BL Lac objects and nuclei of 62 Seyfert, 12 N and 7 normal galaxies. Here has been assumed to be an estimate of the spectral index . On the other hand, has been regarded as a measure of departure from the power law. On the basis of this, the distributions of and in QSOs, BL Lac objects and the nuclei of Seyfert, N and normal galaxies have been studied. The value of depends mainly on the balance of the energy loss due to synchrotron radiation and the rate of replenishment of energy by injection of high energy electrons in the radiating region. The increase in the value of and therefore that of indicates that the activity in the object is slowing down and the object is growing older. Assuming that the QSOs, BL Lac objects and the nuclei of Seyfert, N and normal galaxies essentially represent different phases in the evolutionary sequence of extragalactic objects, we suggest that they may be arranged in the sequence: QSOsBL Lac objects Seyferts 1N galaxies Seyferts 2 Normal galaxies in the decreasing order of activity in the core or nuclei of these objects.On leave of absence from the Government Science College, Rajpur, M.P., India.     

Spectrophotometric observations of delta Capricorni

Spectrophotometric observations of the eclipsing binary system Capricorni, covering the wavelength interval 3300–7300 Å, have been presented. Comparison of the standard spectral scans of Cap with the spectral scans of the stars of known spectral types and luminosity classes taken from the Breger (1976) catalogue shows that, near the phase of secondary eclipse, Cap shows the spectral-luminosity type as A8-9III. This is in agreement with the photometric findings of Srivastava (1987b). H emission is not visible convincingly, however, some irregularities are apparent, at least in two scans, around the H region.     

A study of the nature of the Hα-emission stars LkHα112, 115, 118, and 119

The present study of the nature of the stars LkH112, LkH115, LkH118, and LkH119 is based on low-dispersion IDS spectra and photometric measurements in the wavelength range between 0.33 and 3.8 m. These stars are located in the direction of the extremely young open cluster NGC 6530 (Walker, 1957). The purpose of this study is, in general, to know whether they belong to the group of intermediate mass pre-main sequence objects, also known as Herbig Ae/Be stars, and, in particular, what special characteristics they possess. The result is as follows. The stars are very young; probably only LkH112 and LkH115 are members of the above-mentioned class of objects. The membership of LkH118 and LkH119 in this group is doubtful.Based on observations made at the European Southern Observatory, La Silla, Chile.     

Theory of the Trojan asteroids,IV

In a previous publication (1977) the author has constructed a family () of long-periodic orbits in the Trojan case of the restricted problems of three bodies. Here he constructs the domain of the analytical solution of the problem of the motion, excluding the vicinity of thecritical divisor which vanishes at the exact commensurability of the natural frequencies ₁ and ₂. In terms of thecritical masses m_j(₂), or the associatedcritical energies _j ² (m), is the intersection of the intervals ofshallow resonance, of the form. Inasmuch as the intervals |₂– _j ² |<_j ofdeep resonance aredisjoint, it follows that (1) the disjointed family () embraces the tadpole branch, 0²1, lying in: and (2) despite the clustering of _j ² (m) atj=, the family () includes, for ²=1, an asymptoticseparatrix that terminates the branch in the vicinity of the Lagrangian pointL ₃.In a similar manner, the family () can be extended to the horseshoe branch 1<_{2 2} ² .     

Magnetic fields and helium-D3 spectroheliograms

Spectroheliograms, having a resolution approaching 2, have been obtained which show He-D₃ in absorption against the disk. The He-D₃ features are compared with the distribution of magnetic fields and with H structures. The brightest regions in H usually show the strongest D₃ absorption. Most H dark filaments show some D₃ absorption, but the degree of correlation varies from filament to filament. The correlation between B_II and He-D₃ absorption is rather poor and the He features are much more diffuse than the photospheric magnetic field.     

Late-time emission of the type II Supernovae powered by the radioactive decay56Ni−56Co−56Fe

A one-zone model for the late time SN II energized by the radioactive decay⁵⁶Ni–⁵⁶Co–⁵⁶Fe is presented. The model succeeds in reproducing for the late time evolution of H and [Oi] 6300 emission lines in SN1970g for the reasonable set of parameters: mass of ejecta 4M , boundary velocityv ₀=4000 km s^–1 and amount of⁵⁶NiM _Ni=0.02M . However, a one-zone model does not account for the late time continuum. In the case of SN1980k the radioactive model fits H and [Oi] 6300 emissions att250 day satisfactory but fails at very late time, e.g.,t=670 day when the predicted value of the ratioL(H)/L(6300) is two orders of magnitude smaller than the observed one. We suggest that the strong H emission in SN1980k on the 670th day is due to the interaction of the supernova envelope with the pre-SN wind. The radioactive model for the late time SN II predicts strong Mgii 2800 line and detectable Hei 10830 line in emission and absorption.     

Evidence for enhanced star formation in iras-detected markarian galaxies

The IR emission of 640 Markarian galaxies (MrkG), included in the IRAS Survey, is considered as an evidence for enhanced star formation rate (SFR) in these objects. About 73% of the MrkG have high far-infrared luminosities (ca. 10E + 44 erg s^–1) in 1–500 mcm IR spectral band. The distribution of log(f ₆₀/f ₁₀₀), peaked at about 45 K, shows that IRAS MrkGs have a tendency to extend the relationf ₆₀/f ₁₀₀ vsL _ir/L _bifor normal S glaxies. They emit up to hundred times more IR energy in 40–120 mcm band than in optics. The mean ratio log L _ir/L _b for 621 IRAS MrkG with known redshifts is 2.2.It is suggested that there are two IR emitting components in the IRAS MrkG - a warm one connected with the UV-fluxes of the newborn massive stars, re-radiated by dust, and a cool one, originated from the dust in galactic disks and heated by the general interstellar radiation field. The warm IR luminosities and warm IR fractions are determined on the basis of IR colour-colour diagrams(25/12),(60/25), and(100/60). The mean warm IR fraction for all Mrk IRAS detected galaxies with well-defined IR fluxes is 0.83 when the grain mass absorption coefficient model withn = 0.0 is used. The dust mass responsible for the IR flux at 60 mcm is derived to be about 10E + 5M , assuming the dust clouds are optically thin, and using the dust temperatureT _d 46 K (deduced from thef(60)/f(100) ratio). There is a relation betweenL _irandL _blwhich points out that the most IRAS MrkG have rather enhanced SFR.     

Asymptotic properties of disk dynamo

The asymptotic properties of a turbulent disk dynamo at large dimensionless numbersR andR characterizing the helicity and the differential rotation are analysed. Three types of generations in the dependence of the relations betweenR andR are found: ²-dynamo and two types of -dynamo. For each of these types the rates of growth are obtained and the forms of solution are pointed out. Boundaries of the disk dynamo approximation are given.     

Effects of Hall current on hydromagnetic free-convective flow through a porous medium

An analysis of the effects of Hall current on hydromagnetic free-convective flow through a porous medium bounded by a vertical plate is theoretically investigated when a strong magnetic field is imposed in a direction which is perpendicular to the free stream and makes an angle to the vertical direction. The influence of Hall currents on the flow is studied for various values of .Nomenclature c _p specific heat at constant pressure - e electrical charge - E Eckert number - E electrical field intensity - g acceleration due to gravity - G Grashof number - H ₀ applied magnetic field - H magnetic field intensity - (j _x , j _y , j _z ) components of current densityJ - J current density - K permeability of porous medium - M magnetic parameter - m Hall parameter - n _e electron number density - P Prandtl number - q velocity vector - (T, T _w , T ) temperature - t time - (u, v, w) components of the velocity vectorq - U ₀ uniform velocity - v ₀ suction velocity - (x, y, z) Cartesian coordinates Greek Symbols angle - coefficient of volume expansion - _e cyclotron frequency - frequency - dimensionless temperature - thermal conductivity - coefficient of viscosity - magnetic permeability - kinematic viscosity - mass density of fluid - _e charge density - electrical conductivity - _e electron collision time     

Singposts of shock waves in the metagalactic medium

Explosions of quasars and young galaxies at large redshifts must cause propagation of blast waves in the metagalactic medium. The shock waves formed can, during the radiative cooling stage, produce dense cold spherical shells around the epicentres of explosions. But, even before that, at the stage of adiabatic expansion, each spherical shock-wave front, if it lies on one line-of-sight with a more distant quasar, can imprint into the quasar spectrum a specific absorption doublet with a distance between the components (in the rest frame) ₀ 3 Å. The L doublet components have a small but the same equivalent widthW ₀ 0.3 Å, the ratioW ₀/₀ weakly depending onW ₀ ifW ₀ is small. We demonstrate here that such absorption L doublets are really present among the L forest in the absorption spectra of distant quasars which are, according to Sargentet al. (1980), of mostly intervening (and not intrinsic) origin. Further accumulation of data on absorption doublets, which can serve as direct indicators of metagalactic shock-waves, may provide valuable information about the physical conditions in the metagalactic gas at large redshifts.     

Investigation of Galaxies of the Second Byurakan Sky Survey. IV. Spectroscopic Observations in the Fields of 11h30m, +59° and 12h00m, +59°

Spectroscopic observations of 71 objects have completed the follow-up spectroscopy of galaxies in two adjacent fields of the Second Byurakan Survey with central coordinates = 11^h30^m, = +59° and = 12^h00^m, = +59°. The spectra were obtained on the 2.6-m telescope of the Byurakan Astrophysical Observatory and the 6-m telescope of the Special Astrophysical Observatory. The redshifts and absolute stellar magnitudes of all the galaxies have been determined. The objects have been classified using an adapted scheme.     

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.     

The brightness distribution over the moon's disk at 6 cm wavelength

On November 27, 1974, a map of the Moon was obtained at 6 cm wavelength with the 100-m-telescope in Effelsberg. The high angular and favourable temperature resolution allowed an interpretation of the observed brightness distribution. The dominant feature of the brightness distribution is the centre-to-limb variation, particularly noticeable in the direction of the poles. The exponent of the commonly adopted cos ()-law, describing the temperature variation across the lunar disk, is determined as 0.4. The North-South variation of the lunar surface temperature is estimated to be 30%; the depth of penetration (L _e) of electromagnetic waves of 6 cm wavelength is found to beL _e 17 m.     

A comparison of the near-ultraviolet continuum and chromospheric emission line fluxes of the late-type giant stars

We investigate the near-ultraviolet high-resolution LWR spectra of the stars Cas, And, Tau, Gem, Cru, Boo, and Peg, obtained with the aid of the International Ultraviolet Explorer Satellite. We have given here a list of the strongest and most prevalent emission lines in the near-ultraviolet spectra of Boo, KlIIIp, and Peg, M2.5II-III which have the same luminosity class and different spectral type. The near-ultraviolet continuum flux measurements and integrated emission line fluxes of these stars for the 2500–3200 Å region are presented in order to compare the variations in the appearance of the near-ultraviolet flux distribution with the temperature structure of their chromospheres for K and M giant stars. We also discuss differences between observed and calculated fluxes found from the Planck function.     

A deeply embedded companion to LKHα198

The region around the Herbig Ae/Be star LkH198 was imaged at 10m with the CAMIRAS camera at the Canada-France-Hawaii Telescope and the Nordic Optical Telescope. We discovered a deeply embedded companion 6 north of LkH198, which may be responsible for most of the far-infrared emission in the region and for driving the molecular flow. LkH198 appears point-like at our resolution (FWHM 1.3), excluding an extended envelope of transiently heated small grains as the dominant origin of the mid-infrared excess in that star.     

Study of alpha component dynamics in the solar wind using the Prognoz satellite

The analysis of solar wind He⁺⁺ and H⁺ ion distribution functions, collected over five months by the satellite Prognoz 1, shows that these are in general maxwellian but that often tails appear at higher speeds. The existing relation V-T, the observation of ratios of T/Tp 3.83 and V/Vp 1.035 give evidence of preferential He⁺⁺ ion heating and acceleration. The criteria for heating by dissipation of hydromagnetic waves proposed by Barnes and Hung (1973) are tested experimentally. Finally, multifluid models are likely to predict certain observations such as dependence of the velocity ratio V/Vp on the solar wind flux.     

Hα line emission and infrared excess in Be stars

The H observations of a selected sample of bright Be stars are presented. The available infrared observations at K band (2.2 m) of these stars have been used to find the infrared excess emission. The analysis of the combined data show thatL _H, the luminosity of the H emission line, is proportional toL _IR, the luminosity of the infrared excess emission. The linear correlation betweenL _IR andL _H shows that both the infrared excess and the H line originate in a common region. It is also detected that the infrared excess emission is produced throughout the whole envelope whereas the H is emitted in some defined region of the circumstellar (CS) envelope.     

Filter observations of prominences in the D3 and Hα lines

D₃ and H pictures of prominences were obtained with a 21-in. Lyot coronograph and a Fabry-Perot etalon used as a narrow band filter. The monochromatic images of quiescent, quasiquiescent and loop-prominences were studied. The comparison of the isophotes of quiescent and quasi-quiescent prominences in D₃ with those in H shows the similarity of the prominence structure at both wavelength, although there is a strong tendency for an increase in the intensity ratio D₃/H in the upper region of prominences. It seems that it is due to lower temperature in the upper regions of prominences. Probably, the relaxation processes establishing ionization equilibrium play some role. Measurements of the knot intensities of the loop-prominence show strong variations of the intensity ratio D₃/H (more than one order of magnitude).     

The behaviour of the infrared lines of neutral oxygen and the balmer lines of hydrogen in the spectra of early-type stars with emission lines

The equivalent widths of the oxygen lines at 7774 and 8446 and of H (and some H) have been measured for 22 early-type, emission-line stars. A strong correlation between H and 8446 intensities has been found, although there is no such correlation between H and 7774. This confirms the probability that Bowen's mechanism is operative (the neutral oxygen 3³ D state is overpopulated because the excitation energy of Ly- nearly coincides with that of theOi 1025 line). The possibility of using 8446 and H equivalent widths for a comparison of oxygen to hydrogen abundances in these stars is discussed.