The Supercritical Accretion Disk of SS 433

The structure of the SS 433 supercritical accretion disk derived from spectral and photometric data is described. In the disk plane, gas outflows at a velocity of about 100-150 km/s, while above the disk plane, the velocity increases sharply and reaches 1500 km/s at polar angle 60°. The outer parts of the accretion disk are involved in the precessional motion, which means that the slaved disk precession model is correct. There is complex periodic variability in the radial velocities of SS 433. Apart from the well-known precessional and orbital variability, the strongest cycle is 1/7 of the precession period, P7 = 23.228 ± 0.005 days. This is interpreted as evidence for a spiral shock in the accretion disk. The He II 4686 line consists of two components: a stream-formed narrow Gaussian profile and a broad double-peaked one. The latter is completely eclipsed at phase 0.0. Its blue and red peaks are probably emitted in gaseous cocoons around the bases of the relativistic jets. A correct value of the mass function has been found, which shows that the optical star is massive. The relativistic star's mass is estimated to be Mx 6M.     

Continuum radiation from active galactic nuclei

Summary Active galactic nuclei (AGN) can be divided into two broad classes, where the emitted continuum power is dominated either by thermal emission (radio-quiet AGN), or by nonthermal emission (blazars). Emission in the 0.01–1 m range is the primary contributor to the bolometric luminosity and is probably produced through thermal emission from an accretion disk, modified by electron scattering and general relativistic effects. The 1–1000 m continuum, the second most important contributor to the power, is generally dominated by thermal emission from dust with a range of temperatures from 40 K to 1000–2000 K. The dust is probably reemitting 0.01–0.3 m continuum emission, previously absorbed in an obscuring cone (or torus) or an extended disk. The 1–10 keV X-ray emission is rapidly variable and originates in a small region. This emission may be produced through Compton scattering by hot thermal electrons surrounding an accretion disk, although the observations are far from being definitive. The weak radio emission, which is due to the nonthermal synchrotron process, is usually elongated in the shape of jets and lobes (a core may be present too), and is morphologically distinct from the radio emission of starburst galaxies.In the blazar class, the radio through ultraviolet emission is decidedly non-thermal, and apparently is produced through the synchrotron process in an inhomogeneous plasma. The plasma probably is moving outward at relativistic velocities within a jet in which the Lorentz factor of bulk motion (typically 2–6) increases outward. This is inferred from observations indicating that the opening angle becomes progressively larger from the radio to the optical to the X-ray emitting regions. Shocks propagating along the jet may be responsible for much of the flux variability. In sources where the X-ray continuum is not a continuation of the optical-ultraviolet synchrotron emission, some objects show variability consistent with Compton scattering by relativistic electron in a large region (in BL Lacertae), while other objects produce their X-ray emission in a compact region, possibly suggesting pair production.When orientation effects are included, all AGN may be decomposed into a radio-quiet AGN, a blazar, or a combination of the two. Radio-quiet AGN appear to have an obscuring cone or torus containing the broad emission line clouds and an ionizing source. Most likely, the (non-relativistic) directional effects of this obscuring region give rise to the difference between Seyfert 1 and 2 galaxies or narrow and broad line radio galaxies. For different orientations of the nonthermal jet, relativistic Doppler boosting can produce BL Lacertae objects or FR I radio galaxies, or at higher jet luminosities, flat-spectrum high-polarization quasars or FR II radio galaxies.     

Gas Dissipation from the Protosatellite Disk of Jupiter

We consider the dissipation of the gaseous component from the gas–dust accretion disk of Jupiter in which the Galilean satellites were formed. The thermal dissipation of hydrogen and helium is shown to be ineffective. It could ensure the loss of gas only for a low-mass disk and only if the rarefied outer layers of the disk are heated to 10⁴ K. Such a high disk temperature is not reached through Jupiter's radiation in existing models of its formation, but it could be provided by UV radiation of the early Sun after the dissipation of the protoplanetary disk. The viscous dissipation (with a viscosity parameter 10^–3 in the -disk model) related to disk accretion onto Jupiter could disperse a low-mass disk in 10⁷ years. A magnetocentrifugal mechanism, which produced a disk wind during accretion capable of carrying away 0.1 of the accreted gas mass, was probably also involved in the dispersal of the Jovian disk. Differential dispersion, with the loss of only hydrogen and helium and the retention of water vapor and heavier gases in the disk, is possible only in a low-mass disk model. We conclude that the water contained in the Galilean satellites was brought in mainly by solid planetesimals captured into the disk during mutual inelastic collisions in Jupiter's sphere of influence.     

Радиоизлучение Быстрых космических ионов

, . () . , , , . ( ), , , . . (2.7). ( ₁ k ₁ ,V — , — .) (k ₁) (k) §2 ( (2.14)). , (3.6) (3.4), (3.8) . (3.9)–(3.13) ( (3.9), (3.10) (3.11) , (3.12)–(3.13) ). (3.14), (3.16)–(3.19). - . (3.15). ( (4.14)–(4.15)). (4.23)–(4.25). (4.26)–(4.28). §5. , . ((5.5)–(5.6)). , . (5.10) .     

Planetary accretions in jet streams

The problem of planetary accretion in a jet stream is studied using the model developed by Alfvén and Arrhenius. We find that there are basically three types of planetary accretion: namely, fast process _c < _i , slow process _c ~ _i and delayed process _c > _i where _c is the characteristic time of the occurrence of catastrophic accretion and _i the time-scale of mass injection to the planetary system (3×10⁸ yr). These different time scales of accretion are found to be closely related to the primordial thermal profiles and equatorial inclinations of the planets. Finally, Venus' retrograde rotational spin is shown to be a possible result of accretion process in a jet stream.     

Circumstellar matter in direct impact algol systems

Full-orbit H observations have been analyzed to determine the two-dimensional distribution of the circumstellar gas in the four short-period Algols, U Sge, U CrB, RS Vul, and SW Cyg. In these systems, the gas stream resulting from Roche-lobe overflow directly impacts the mass-gaining star and feeds material into a structure known as a transient accretion disk. The accretion regions observed in these systems include a transient accretion disk that at least partially surrounds the mass gainer, the gas stream, and possibly a chromospheric component associated with the magnetically active cool star.     

Dynamical Processes in the Neighborhood of the Herbig Ae Star MWC 480 Based on Spectral Monitoring Data

Spectral observations of the Herbig Ae star MWC 480 are reported. Observations were made on the 2.6 m telescope at the Crimean Astrophysical Observatory and the 6 m telescope at the Special Astrophysical Observatory in the neighborhoods of the sodium resonance doublet, the He I 5876 line, the oxygen O I 7774 line, the H line, and some others. The H line has a P Cyg-type profile which is typical of anisotropic decelerated material outflows. The parameters of the line profile vary on a time scale on the order of days or longer. The blue wing of the line profile, in which noticeable changes are detectable over times of a few hours, is subject to the greatest variation. An unusual line shape is observed in the sodium lines. Their profiles resemble type P Cyg profiles with discrete absorption components can be seen in the blue wing. The number, shape, and radial velocities of the components change with time. The maximum radial velocity is -330 km/s and the minimum, about -50 km/s. The high velocity components are subject to the greatest variability. An analysis of the spectral variability yields the following conclusions: (1) the inner layers of the accretion disk of MWC 480 reach right to the star. The maximum rotation velocity of the circumstellar gas derived from the oxygen OI 7774 line shape is close to 400-500 km/s, which corresponds roughly to the radius of the last Keplerian orbit. (2) A highly nonuniform, high velocity component of the disk wind, which contains dense fragments (microjets), develops in this region. They appear to form as a result of the unstable structure of the magnetic field in the layers of the accretion disk closest to the star. (3) The maximum velocities of the microjets are only slightly higher than the escape velocity at the star's surface. Thus, the bulk of the momentum which they acquire is expended in overcoming the star's gravity and this causes a deceleration in the radial motion of the gas. This kind of structure for the radiating region is consistent with magneto-centrifugal models of the disk wind in which the intrinsic magnetic field of the accretion disk plays a dominant role in the acceleration of the gas.     

Particle acceleration and main parameters of ultra-high energy gamma-ray binaries

Analysis and classification of the mechanisms of particle accleration in close binary systems with compact object have been carried out. The region of UHE particles generation is shown to be situated in the accretion column of a neutron star. The mechanism of particle accleration in the accretion column by the electric field of nonlinear magneto-acoustic vortices generated in the accreting plasma with unstable distribution of hollow beam-type is proposed. It is argued that the beam of relativistic particles proves to be essentially collimated. The radius of UHE particle generation is estimated.     

The stability of an anisotropic plasma jet

The modified Chew-Goldenberger-Low equations have been used to study the stability of a resistive anisotropic plasma jet surrounded by a non-conducting compressible gas. The dispersion relation has been obtained and discussed in three limiting situations: (i) , the resistivity vanishingly small, (ii) and (iii) short and long wavelength perturbations. In some cases, the limiting situations 1 or 1 ( is the ratio of the density of the plasma jet to the density of the exterior gas) have been discussed. The conditions for instability have been obtained. It has been found that the resistivity introduces new modes which make the plasma jet overstable. In the limit of large wavelength disturbances, the jet with finite but high conductivity is found to be unstable. For small wavelength disturbances, the jet is found to be unstable.     

Long-Term Spectral Variability of the Herbig Ae-Star HD 179218

The results of high-resolution long-term spectral monitoring of Herbig Ae star HD 179218 in the region of emission H line and the sodium resonance doublet Na I D are presented. The received data show the existence of short-term variability (about 10 days) and long-term wave-like variability of equivalent width EW, intensity of circumstellar (CS) emission I and parameters of H emission profile. The analysis of these data allows us to suppose the existence of the global variability of parameters of accretion disk.     

The First Byurakan Spectral Sky Survey. Late-type stars. VI. The zone+69°≤δ≤+77°

We present the sixth list of red stars selected from the plates of the First Byurakan Spectral Sky Survey. These objects are located in the zone3 ^h 45 ^m 18 ^h and+69°+77°. The list contains data on 42 new objects. We suggest that there exists a dust cloud around 2 of them.Translated fromAstrofizika, Vol. 38, No. 2, 1995.     

Tentative identification of the diffuse interstellar absorption bands and of a diffuse interstellar doublet line

The four diffuse interstellar absorption bands at 4430, 4760, 4890, and 6180 and the two diffuse lines at 5780 and 5797 are interpreted as belonging to pre-ionization transitions in H^– and O^–, respectively. In both cases the identifications are supported by extrapolations of wave numbers of resonance lines along isoelectronic sequences.In the H^– case the hypothesis as to the origin of the bands is supported by quantum-mechanical results byHerzenberg andMandl (1963) as to the positions of resonances in collisions between neutral hydrogen atoms and free electrons. The relatively large intensities of the forbidden transitions indicate that the extent of the ion in its excited states may be very large as compared to ordinary atomic dimensions. In the O^– case the relative doublet separation, as extrapolated along the isoelectronic sequence, is used for the identification of the doublet.     

Theoretical spectra of cataclysmic variables

We present two methods of modelling accretion disks in dwarf novae. The first one determines self-consistently the structure of a disk together with the radiation field. The computed theoretical spectra agree well with the observations of the dwarf nova WX Hyi in quiescence as well as in superoutburst. The second method is a modification of Tylenda's (1981) approach. We have used it to calculate models of disks around main-sequence accretors. The most interesting result is that no unique solution exists for a moderate mass flux around 10^–6 Myr^–1. Such disks are thus probably unstable.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

Soft-thresholding technique and restoration of 3C273 jet

We show that it can be possible to obtain lower limits on the jet Lorentz factors in superluminal very high energy (VHE) -ray blazars (e.g. Mrk, 421) which are more restrict than that ones derived only from the observations of superluminal motion. To do that we need to define some parameters of the blazars (i.e. accretion disk luminosity, disk inner radius, or disk temperature at the inner radius) which can be fixed in some sources based on the optical-UV observations. Moreover the knowledge is required on: (a) the variability time scale of radiation emitted from the shock (blob) region; (b) the maximum energy of emitted -rays; (c) and the value of an apparent speed of the shock from measurements of superluminal motion in the source. Based on the available observations of Mrk 421 and QSO 1633+382 we put constraints on the jet Lorentz factor in these sources as a function of their disk inner radius.     

Study of Hα Jets on the Quiet Sun

High-speed jets of solar quiet regions have been observed at Big Bear Solar Observatory in H–1.0 Ú, and compared with high-resolution magnetograms. Over the whole Sun, the birthrate of the H–1.0 Ú jets is about 19±3 events s^–1, which is much lower than the birthrate of spicules. The average lifetime of these jets is 2±1 min. H–1.0 Ú jets are very different from spicules, in the sense of birthrate, lifetime, and shape. Jets tend to recur in the same sites, always located in boundaries of supergranules. Under the best observing conditions, we found that 80% of the major jet sites are associated with converging magnetic dipoles – mainly the sites where intranetwork elements are canceling with opposite polarity network elements. In order to establish a possible relationship between the disk H jets and limb macrospicules, we have also obtained time sequences of H center-line images at the limb. These images are enhanced by median filtering so that jet structures over the limb are easily studied. We found that these limb H jets (above the spicule forest) repeatedly occur in the same sites, which is the property shared by the disk H–1.0 Ú jets. However, their mean lifetime is 10 min, substantially longer than that of disk jets. Comparison with simultaneous SOHO/EIT Heii 304 Ú images shows that every Heii 304 Ú jet over the limb coincides with an H jet, although Heii 304 Ú jets extend much farther out. Some H jets do not have associated He jets, probably due to the difference in image resolutions. H spectra of selected jets are analyzed, and we found that jets are not simply blue-shifted; instead, the line profiles are broadened with significantly larger broadening on the blue side. Two-component fitting finds that the velocity of the blue-shifted component (an optically-thin component) is around 20 to 40 km s^–1.     

Comparison of thermal and nonthermal hard X-ray emission in electron-heated solar flares

Using the results of numerical simulations of the solar atmospheric response to heating by nonthermal electron beams during solar flares, we have calculated the spatial and temporal evolution of both (i) the direct (beam-target) nonthermal bremsstrahlung and (ii) the thermal bremsstrahlung arising from the hot plasma energized by the electron beam. Typically, we find that below a certain cross-over energy E ^*, the emission is dominated by the thermal component, while at higher energies the direct bremsstrahlung component becomes more important. This cross-over energy is dependent on the position within the loop, generally increasing with height.We have also investigated the dependence of the cross-over energy E ^* on the parameters of the electron energy input. At the time of peak electron flux injection the cross-over energy E ^* can, for plausible parameters, be as high as 52 keV at the top 1 pixel, and as low as 16 keV at the bottom 1 pixel. We conclude that a possible reassessment of SMM HXIS data as an indicator of the thermal or nonthermal character of the primary energy release (based primarily on the geometric properties of the hard X-ray source) is required. Our results also point to the minimum photon energy that future instruments should observe (where practical, giving due consideration to detector sensitivity) in order to be sure that, in the context of the thick-target interpretation, the nonthermal component is not swamped by the self-consistent thermal counterpart created by the beam heating.     

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.     

The May 1985 superoutburst of OY Carinae: I. Structure of the outer disk from optical and IR observations

We present optical and IR observations of the dwarf nova OY Car during the May 1985 superoutburst. From them we find that the superhump has a temperature of 8000K and an area of order half the size of the red dwarf or accretion disk. We also compare the behaviour during two simultaneous optical/IR observations. Whilst the light curves in the two pass bands are similar during one observation, in the other observation they show marked differences that may be due to a cool region in the outer disk.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

Passage of the solar current disk and major geomagnetic storms

It is shown that major geomagnetic storms (¦Dst¦ > 100) tend to develop at about the time of the passage of the solar current sheet or disk at the location of the Earth, provided this passage is associated with (1) a large impulsive increase of the IMF magnitude B, (2) a negative value of the IMF angle (Theta), and (3) an increasing solar wind speed. The passage occurs in association with the 27-day rotation of the warped current disk or a temporal up-down movement of the latter. The period in which ¦Dst¦/t< 0 during major storms coincides approximately with the period when the solar windmagnetosphere energy coupling function becomes 10¹⁹ erg s^–1. These conclusions do not depend on the phase of the sunspot cycle.These results may be interpreted as follows: A high speed solar wind flow, originating either from flare regions or coronal holes, tends to push the solar current disk to move upward or downward for either a brief period (1 3 days) or an extended period (2 weeks). A relatively thin region of a large IMF B > 10 is often present near the moving current disk. Waves are also generated on the moving current disk, and some of them cause large changes of . A high value of is found in the region of a large IMF B near the wavy solar current disk, where has a large negative value.     

Variations of the Chromospheric Network with the Solar Cycle

We have digitized a small sample of Caii K spectroheliograms from the photographic archive of Arcetri Observatory for the period 1950–1970. For each digitized plate, active regions have been automatically identified and masked by applying an algorithm based on the geometrical connection between active pixels. Contrast histograms have been derived for the full disk and for quiet regions. Both of them show a neat Gaussian profile on the dark side and a significant tail on the bright side, due to the brightness enhancements associated with magnetic fields. A solar cycle dependence of the histogram asymmetry is clearly evident in quiet region data, thus confirming that the network component might provide a significant contribution to long-term variations of the total irradiance.