Showing papers in "Astronomy Reports in 2013"

"RadioAstron"-A telescope with a size of 300 000 km: Main parameters and first observational results

Abstract: The Russian Academy of Sciences and Federal Space Agency, together with the participation of many international organizations, worked toward the launch of the RadioAstron orbiting space observatory with its onboard 10-m reflector radio telescope from the Baikonur cosmodrome on July 18, 2011. Together with some of the largest ground-based radio telescopes and a set of stations for tracking, collecting, and reducing the data obtained, this space radio telescope forms a multi-antenna ground-space radio interferometer with extremely long baselines, making it possible for the first time to study various objects in the Universe with angular resolutions a million times better than is possible with the human eye. The project is targeted at systematic studies of compact radio-emitting sources and their dynamics. Objects to be studied include supermassive black holes, accretion disks, and relativistic jets in active galactic nuclei, stellar-mass black holes, neutron stars and hypothetical quark stars, regions of formation of stars and planetary systems in our and other galaxies, interplanetary and interstellar plasma, and the gravitational field of the Earth. The results of ground-based and inflight tests of the space radio telescope carried out in both autonomous and ground-space interferometric regimes are reported. The derived characteristics are in agreement with the main requirements of the project. The astrophysical science program has begun.

The MASTER-II network of robotic optical telescopes. First results

Abstract: The main stages in the creation of the Russian segment of the MASTER network of robotic telescopes is described. This network is designed for studies of the prompt optical emission of gammaray bursts (GRBs; optical emission synchronous with the gamma-ray radiation) and surveys of the sky aimed at discovering uncataloged objects and photometric studies for various programs. The first results obtained by the network, during its construction and immediately after its completion in December 2010, are presented. Eighty-nine alert pointings at GRBs (in most cases, being the first ground telescopes to point at the GRBs) were made from September 2006 through July 2011. The MASTER network holds first place in the world in terms of the total number of first pointings, and currently more than half of first pointings at GRBs by ground telescopes are made by the MASTER network. Photometric light curves of GRB 091020, GRB 091127, GRB 100901A, GRB 100906A, GRB 10925A, GRB 110106A, GRB 110422A, and GRB 110530A are presented. It is especially important that prompt emission was observed for GRB 100901A and GRB 100906A, and thar GRB 091127, GRB 110422A, and GRB 110106A were observed from the first seconds in two polarizations. Very-wide-field cameras carried out synchronous observations of the prompt emission of GRB 081102, GRB 081130B, GRB 090305B, GRB 090320B, GRB 090328, and GRB 090424. Discoveries of Type Ia supernovae are ongoing (among them the brightest supernova in 2009): 2008gy, 2009nr, 2010V, and others. In all, photometry of 387 supernovae has been carried out, 43 of which were either discovered or first observed with MASTER telescopes; more than half of these are Type Ia supernovae. Photometric studies of the open clusters NGC 7129 and NGC 7142 have been conducted, leading to the discovery of 38 variable stars. Sixty-nine optical transients have been discovered.

Infrared emission and the destruction of dust in HII regions

Abstract: The generation of infrared (IR) radiation and the observed IR-intensity distribution at wavelengths of 8, 24, and 100 µm in the ionized hydrogen region around a young, massive star is investigated. The evolution of the HII region is treated using a self-consistent chemical-dynamical model in which three dust populations are included—large silicate grains, small graphite grains, and polycyclic, aromatic hydrocarbons (PAHs). A radiative transfer model taking into account stochastic heating of small grains and macromolecules is used to model the IR spectral energy distribution. The computational results are compared with Spitzer and Herschel observations of the RCW 120 nebula. The contributions of collisions with gas particles and the radiation field of the star to stochastic heating of small grains are investigated. It is shown that a model with a homogeneous PAH content cannot reproduce the ring-like IR-intensity distribution at 8 µm. A model in which PAHs are destroyed by ultraviolet radiation of the star, generating region HII, provides a means to explain this intensity distribution. This model is in agreement with observations for realistic characteristic destruction times for the PAHs.

Types of gaseous envelopes of “hot Jupiter” exoplanets

Abstract: As a rule, the orbital velocities of “hot Jupiters,” i.e., exoplanets with masses comparable to the mass of Jupiter and orbital semi-major axes less than 0.1 AU, are supersonic relative to the stellar wind, resulting in the formation of a bow shock. Gas-dynamical modeling shows that the gaseous envelopes around hot Jupiters can belong to two classes, depending on the position of the collision point. if the collision point is inside the Roche lobe of the planet, the envelopes have the almost spherical shapes of classical atmospheres, slightly distorted by the influence of the star and interactions with the stellar-wind gas; if the collision point is located outside the Roche lobe, outflows from the vicinity of the Lagrangian points L1 and L2 arise, and the envelope becomes substantially asymmetrical. The latter class of objects can also be divided into two types. If the dynamical pressure of the stellar-wind gas is high enough to stop the most powerful outflow from the vicinity of the inner Lagrangian point L1, a closed quasi-spherical envelope with a complex shape forms in the system. If the wind is unable to stop the outflow from L1, an open aspherical envelope forms. The possible existence of atmospheres of these three types is confirmed by 3D numerical modeling. Using the typical hot Jupiter HD 209458b as an example, it is shown that all three types of atmospheres could exist within the range of estimated parameters of this planet. Since different types of envelopes have different observational manifestations, determining the type of envelope in HD 209458b could apply additional constrains on the parameters of this exoplanet.

Fluctuations in the alpha-effect and grand solar minima

Abstract: The parameters of a special type of alpha-effect known in dynamo theory as the Babcock-Leighton mechanism are estimated using the data of sunspot catalogs. The estimates support the presence of the Babcock-Leighton alpha-effect on the Sun. Fluctuations of the alpha-effect are also estimated. The fluctuation amplitude appreciably exceeds themean value, and the characteristic time for the fluctuations is comparable to the period of the solar rotation. Fluctuations with the parameters found are included in a numericalmodel for the solar dynamo. Computations show irregular changes in the amplitudes of the magnetic cycles on time scales of centuries and millennia. The calculated statistical characteristics of the grand solar minima and maxima agree with the data on solar activity over the Holocene.

Analysis of determinations of the distance between the sun and the galactic center

Abstract: The paper investigates the question of whether or not determinations of the distance between the Sun and the Galactic center R 0 are affected by the so-called “bandwagon effect”, leading to selection effects in published data that tend to be close to expected values, as was suggested by some authors. It is difficult to estimate numerically a systematic uncertainty in R 0 due to the bandwagon effect; however, it is highly probable that, even if widely accepted values differ appreciably from the true value, the published results should eventually approach the true value despite the bandwagon effect. This should be manifest as a trend in the published R 0 data: if this trend is statistically significant, the presence of the bandwagon effect can be suspected in the data. Fifty two determinations of R 0 published over the last 20 years were analyzed. These data reveal no statistically significant trend, suggesting they are unlikely to involve any systematic uncertainty due to the bandwagon effect. At the same time, the published data show a gradual and statistically significant decrease in the uncertainties in the R 0 determinations with time.

Turbulent entrainment at the boundaries of the convective cores of main-sequence stars

Abstract: Extra mixing of matter in stellar interiors at the boundaries of the convective cores of mainsequence stars is considered for the first time using the physical model of turbulent entrainment developed by Arnett and collaborators based on three-dimensional hydrodynamical simulations. The model takes into account the energy that goes into mixing the matter of the convective core and layers stable against convection located above the core. It is shown that the extent of the region of extra mixing expressed in units of the pressure scale height is not constant, and decreases as the star evolves along the main sequence. Adequate allowance for extra mixing at the boundaries of convective cores is necessary to clarify the relative importance of different mixing mechanisms in stellar interiors, as well as to determine stellar parameters using asteroseismlogy.

Results of long-term monitoring of 3C 273 over a wide range of wavelengths

Abstract: The results of long-term monitoring of the quasar 3C 273 at wavelengths from radio to gamma rays between 1963 and 2011 are presented. The variations of the source flux density are studied using harmonic and wavelet analysis techniques. The values and frequency-time localizations of harmonic components in the flux-density variations are determined. The eight-year radio-variability period reported earlier had become gradually reduced and attenuated by 2000. The optical light curve has a component with a quasi-period of approximately 13 years. Cyclic variations whose periodicity gradually increased from approximately one to two years were observed in the X-ray between 1996 and 2006. The relative time delays between the light curves at different radio frequences are determined. The frequency dependence of time delays is approximated by the power law, ΔT(ν) ∝ ν −1/k with k = 1.4 ± 0.1, which can be used to infer the corresponding core shift and estimate the core-region magnetic field as B 1 pc = 0.5 ± 0.1 G. This approach is preferable to other methods, since it does not require multi-frequency VLBI observations and is a simple and effective tool for studying Active Galactic Nuclei.

Propagation of a fast magnetoacoustic shock wave in the magnetosphere of an active region

Abstract: The propagation of a fast magnetoacoustic shock wave the magnetosphere of a solar active region is considered the nonlinear geometrical acoustics approximation. The magnetic field is modeled as a subphotospheric magnetic dipole embedded in the radial field of the quiet corona. The initial parameters of the wave are specified at a spherical surface in the depths of the active region. The wave propagates asymmetrically and is reflected from regions of the strong magnetic field, which results in the radiation of the wave energy predominantly upwards. Substantial gradients in the Alfven speed facilitate appreciable growth in the wave intensity. Non-linear damping of the wave and divergence of the wave front lead to the opposite effect. Analysis of the joint action of these factors shows that a fast magnetoacoustic perturbation outgoing from an active region can correspond to a shock wave of moderate intensity. This supports the scenario in which the primary source of the coronal wave is an eruptive filament that impulsively expands in the magnetosphere of an active region.

Spectroscopy of 13 high-mass stars in the Cyg OB2 association

Abstract: The NES echelle spectrograph of the 6-m telescope of the Special Astrophysical Observatory has been used to obtain high-resolution spectra for 13 hot O3-B4 stars in the Cyg OB2 association, making it possible to study weak spectral features of stellar and interstellar origin. Velocity fields in the atmospheres and interstellar medium, characteristics of optical spectra and line profiles are investigated. The cascade star-formation scheme for the association is confirmed. Evidence is presented suggesting that the hypergiant Cyg OB2 No. 12 is an LBV object and that its anomalous reddening has a circumstellar nature.

The interplanetary magnetic field: Radial and latitudinal dependences

Abstract: Results of the analysis of spacecraft measurements at 1–5.4 AU are presented within the scope of the large-scale interplanetary magnetic field (IMF) structure investigation. The work is focused on revealing of the radial IMF component (B r ) variations with heliocentric distance and latitude as seen by Ulysses. It was found out that |B r | decreases as ∼r −5/3 in the ecliptic plane vicinity (±10° of latitude), which is consistent with the previous results obtained on the basis of the analysis of in-ecliptic measurements from five spacecraft. The difference between the experimentally found (r −5/3) and commonly used (r −2) radial dependence of B r may lead to mistakes in the IMF recalculations from point to point in the heliosphere. This can be one of the main sources of the “magnetic flux excess” effect, which is exceeding of the distantly measured magnetic flux over the values obtained through the measurements at the Earth orbit. It is shown that the radial IMF component can be considered as independent of heliolatitude in a rough approximation only. More detailed analysis demonstrates an expressed |B r | (as well as the IMF strength) increase in the latitudinal vicinity of ±30° relative to the ecliptic plane. Also, a slight increase of the both parameters is observed in the polar solar wind. The comparison of the B r distributions confirms that, at the same radial distance, B r values are higher at low than at high latitudes. The analysis of the latitudinal and radial dependences of the B r distribution’s bimodality is performed. The B r bimodality is more expressed at high than in the low-latitude solar wind, and it is observed at greater radial distances at high latitudes. The investigation has not revealed any dependence between B r and the solar wind speed V. The two-peak distribution of the solar wind speed as measured by Ulysses is a consequence of a strong latitudinal and solar cycle dependence of V. It is shown that the solar wind speed in high latitudes (above ±40°) anti-correlates with a solar activity: V is maximum during solar-cycle minima and minimum at the maximum of solar activity.

Class I methanol masers in low-mass star-forming regions

Abstract: Results of observations of Class I methanol masers in regions of low-mass star formation (MMIL) are summarized and analyzed. Four masers were detected at 44, 84, and 95 GHz towards "chemically active" bipolar outflows in the low-mass star-forming regions NGC1333 I4A, NGC 1333 I2A, HH 25, and L1157. Another maser was found at 36 GHz towards a similar outflow in NGC 2023. Thus, all the detected MMILs are associated with chemically active outflows. The brightness temperatures of the strongest 44-GHz maser spots in NGC 1333 I4A, HH 25, and L1157 exceed 2000 K, whereas the brightness temperature in NGC 1333 I2A is only 176 K, although a rotational-diagram analysis shows that this last source is also amaser. The flux densities of the newly detectedmasers are no higher than 18 Jy, and are much lower than those of strong masers in regions of high-mass star formation (MMIH). The MMIL luminosities match the maser luminosity-protostar luminosity relation established earlier for MMIHs. No MMIL variability was detected in 2004-2011. The radial velocities of the newly detected masers are close to the systemic velocities of the associated regions, except for NGC 2023, where the maser radial velocity is lower than the systemic velocity by approximately 3.5 km/s. Thus, the main MMILproperties are similar to those of MMIHs. MMILs are likely to be an extension of the MMIH population toward lower luminosities of both the masers and the associated young stellar objects. The results of VLA observations of MMILs can be explained using a turbulent-cloud model, which predicts that compact maser spots can arise in extended sources because the coherence lengths along some directions randomly appear to be longer than the mean coherence length in a turbulent velocity field. However, one must assume that the column density of methanol towardM1, the strongest maser in L1157, is appreciably higher than the mean column density of the clump B0a where the maser arises. The shape of the maser lines in L1157, forming double profiles with a red asymmetry, may indicate that the masers arise in collapsing clumps. However, although this model may be correct for L1157, it is specific to this source, since none of the other masers observed exhibited a double profile.

The spin-down mechanism of the X-ray pulsar 4U 2206+54

Abstract: Observations of the X-ray pulsar 4U 2206+54 obtrained over 15 years show that its period, which is now 5555 ± 9 s, is increasing dramatically. This behavior is difficult to explain using traditional scenarios for the spin evolution of compact stars. The observed spin-down rate of the neutron star in 4U 2206+54 is in good agreement with the value expected in a magnetic-accretion scenario, taking into account that, under certain conditions, the magnetic field of the accretion stream can affect the geometry and type of flow. The neutron star in this case accretes material from a dense gaseous slab with small angular momentum, which is kept in equilibrium by the magnetic field of the flow itself. A magnetic-accretion scenario can be realized in 4U 2206+54 if the magnetic-field strength at the surface of the optical counterpart to the neutron star is higher than 70 G. The magnetic field at the surface of the neutron star is 4 × 1012 G in this scenario, in agreement with estimates based on an analysis of X-ray spectra of the pulsar.

Analysis of the fine temporal structure of optical flares on AD Leo on February 4, 2003

Abstract: The fine temporal structure of two flares observed on the red-dwarf flare star AD Leo on February 4, 2003 with the 1.25-m telescope of the Crimean Astrophysical Observatory in a rapidphotometry mode is studied. One flare lasted approximately 5 min and another was longer than 8 min. The amplitudes in the U band were 1.65m and 1.76m. A detailed color analysis shows that the flare parameters at the maximum brightnesses corresponded to blackbody radiation with temperatures of approximately 14 000 and 13 000 K, enabling the monitoring of temperature — the rapid cooling of flare plasma near the flare maxima—for the first time. During 1.5 and 3.5 min at the maxima, the flares radiated as blackbodies, but these behaved as optically thick plasmas in the Balmer continuum on the second half of the descending branches. At the end of the first flare, the plasma became optically thin in the Balmer continuum; the final stage of the second flare was not observed. The flare areas at the luminosity maxima were 2.1 × 1018 and 3.0×1018 cm2 in a blackbody approximation, or 0.07%and 0.11%of the visible stellar disk. The occurrence of quasi-periodic brightness pulsations during red-dwarf flares on time scales of approximately ten seconds is confirmed.

The magnetospheric structure of radio pulsars with interpulses

Abstract: Pulsars with interpulses—pulse components located between the main pulses—are studied. About 50 such objects are currently known. Methods developed earlier to determine the angle β between the rotation axis and the magnetic moment of the neutron star are used to investigate the geometry of the magnetospheres in these objects. In a number of pulsars, β < 20°, so that not only interpulses, but also radiation between pulses and a correlation between the behaviors of the interpulses and main pulses, is expected. In other pulses, this angle is greater than 60°, and interpulses can appear if the radiation cone is sufficiently broad and there is a favorable orientation of the line of sight of the observer. Thus, the earlier prediction that there should be two types of pulsars with interpulses—aligned and orthogonal—is supported. Estimates of the ages of the pulsars in these two groups indicate that aligned rotators are appreciably older than orthogonal rotators.

Modeling of the formation of complex molecules in protostellar objects

Abstract: The results of molecular composition modeling are presented for the well studied low-mass star-forming region TMC-1 and the massive star-forming region DR21(OH), which is poorly studied from a chemical point of view. The column densities of dozens of molecules, ranging from simple diatomic to complex organic molecules, are reproduced to within an order of magnitude using a one-dimensional model for the physical and chemical structure of these regions. The chemical ages of the regions are approximately 105 years in both cases. The main desorption mechanisms that are usually included in chemical models (photodesorption, thermal desorption, and cosmic-ray-induced desorption) do not provide sufficient gasphase abundances of molecules that are synthesized in surface reactions; however, this shortcoming can be removed by introducing small amount of reactive desorption into the model. It is possible to reproduce the properties of the TMC-1 chemical composition in a standard model, without requiring additional assumptions about an anomalous C/O ratio or the recent accretion of matter enriched with atomic carbon, as has been proposed by some researchers.

K-Corrections to radial-velocity curves of optical components in X-ray binaries. Massive systems with weak X-ray heating

Abstract: The radial-velocity curves of optical components in X-ray binary systems can differ from the radial-velocity curves of their barycenters due to tidal distortion, gravitational darkening, X-ray heating, etc. This motivated us to investigate how the semi-amplitudes of the radial-velocity curves of these optical components can depend on the binary-system parameters in a Roche model. The K correction is taken to be the ratio of the radial velocity semi-amplitude for a star in the Roche model to the corresponding value for the stellar barycenter. K corrections are tabulated for the optical stars in the massive X-ray binaries Cen X-3, LMC X-4, SMC X-1, Vela X-1, and 4U 1538-52.

Modeling and analysis of the spectrum of the globular cluster NGC 2419

Abstract: The properties of the stellar population of the unusual object NGC 2419 are studied; this is the most distant high-mass globular cluster of the Galaxy’s outer halo, and a spectrum taken with the 1.93-m telescope of the Haute Provence Observatory displays elemental abundance anomalies. Since traditional high-resolution spectroscopicmethods are applicable to bright stars only, spectroscopic information for the cluster’s stellar population as a whole, integrated along the spectrograph slit placed in various positions, is used. Population synthesis is carried out for the spectrum of NGC 2419 using synthetic spectra calculated from a grid of stellar model atmospheres, based on the theoretical isochrone from the literature that best fits the color-magnitude diagram of the cluster. The derived age (12.6 billion years), metallicity ([Fe/H] = −2.25 dex), and abundances of helium (Y = 0.26) and other chemical elements (a total of 14) are in a good qualitative agreement with estimates from the literature made from high-resolution spectra of eight red giants in the cluster. The influence on the spectrum of deviations from local thermodynamic equilibrium is considered for several elements. The derived abundance of α-elements ([α/Fe] = 0.13 dex, as the mean of [O/Fe], [Mg/Fe], and [Ca/Fe]) differs from the mean value in the literature ([α/Fe] = 0.4 for the eight brightest red giants) and may be explained by recently discovered in NGC2419 large [a/Fe] dispersion. Further studies of the integrated properties of the stellar population in NGC 2419 using higher-resolution spectrographs in various wavelength ranges should help improve our understanding of the cluster’s chemical anomalies.

On the Calculation of Mean-Weighted Value in Astronomy

Abstract: Although the calculation of the weighted mean of several individual values (one of the most frequently used operations in scientific analysis) is straightforward, the calculation of the corresponding uncertainty does not always receive the attention it requires. The application of methods of classical statistics to real observational data is often not justified, since the assumptions lying at the basis of these methods are not satisfied. The presence of systematic uncertainties in the averaged measurements and underestimation of the corresponding random errors used to define the weights are typical examples. A new approach to calculating the uncertainty of weighted mean based on a combination of known methods is considered. The proposed method makes it possible to automatically take into account both the random errors and scatter of the input data, making the method suitable for determining realistic errors for mean values in the case of observational data displaying both good and poor consistency.

Global complexes of activity

Abstract: A new concept of “Global Complexes of Activity” on the Sun is presented, which brings together objects associated with both global and local fields in a single framework. Activity complexes have traditionally been identified purely from observations of active regions. We show here that a global complex also includes coronal holes and active regions. Our analysis is based on a large dataset on magnetic fields on various scales, SOHO/MDI observations of active regions and magnetic fields, and UV observations of coronal holes. It is shown that the evolution of coronal holes and active regions are parts of a single process. The relationships between the fields on different scales during the generation of the cycle is discussed.

A possible mechanism for the formation of tilted disks in intermediate polars

Abstract: Using 3D gas dynamics, we numerically simulate accretion-disk formation in typical cataclysmic variable intermediate polars with dipolar magnetic fields (B a = 105−5 × 105 G) and misaligned white-dwarf magnetic and rotation axes. Our simulations confirm that a significant misalignment of the axes results in a significant misalignment of the disk to the orbital plane. However, over time, this disk tilt disappears: early in the simulation, the initial particle positions in the rarefied tilted disk are governed solely by the magnetic field of the white dwarf. Due to the increasing disk mass and hence increasing disk gas pressure, the tilted disk eventually becomes decoupled from the magnetic field. The tidal action of the donor leads to a retrograde (i.e., nodal) precession of the tilted disk’s streamlines, and the disk becomes twisted. When the disk tilt is greater than 4°, the incoming gas stream no longer strikes the disk rim (i.e., bright shocked region). Matter is now transported over and under the disk rim to the inner regions of the disk. Over time, the increased mass of inner parts of the disk due to the action of the colinear gas stream returns the inner-disk regions to a colinear configuration. Meanwhile, the outer regions of the tilted, twisted disk become warped. Our simulations suggest that the lifetime of an intermediate polar’s tilted disk could be several tens to thousands of orbital periods.

Doppler tomography in three dimensions. Problems of realization

Abstract: Three-dimensional (3D) Doppler tomography is used to study the motions of gas flows in interacting stellar binary systems. This is achieved by applying a reconstruction method developed for few projections tomography, sometimes referred to as the radioastronomical approach (RA). An analysis of the geometry of the spatial arrangement of the aspects during the reconstruction of 3D tomograms using onedimensional profiles without the intermediate stage of constructing two-dimensional sections is presented. A method for estimating possibilities for reconstructing 3D tomograms based on the appearance of the summarized transfer function is proposed and justified. The influence of the inclination of the system on the resolutions along the main axes is considered. The number of aspects required to achieve a quality of the recontruction comparable to 2D versions is estimated. A comparative analysis of possible distortions of 2D and 3D Doppler tomograms in the presence of flow motions extending beyond the orbital plane is carried out. The analysis indicates the advantages of the 3D method. A summary of first observational results taking into account the velocity component perpendicular to the orbital plane of the binary system, Vz, is presented.

Supermassive black holes and central star clusters: Connection with the host galaxy kinematics and color

Abstract: The relationship between the masses of the central, supermassive black holes (M bh) and of the nuclear star clusters (M nc) of disk galaxies with various parameters galaxies are considered: the rotational velocity at R = 2 kpc V (2), the maximum rotational velocity V max, the indicative dynamical mass M 25, the integrated mass of the stellar populationM *, and the integrated color index B-V. The rotational velocities andmasses of the central objects were taken from the literature. ThemassM nc correlatesmore closely with the kinematic parameters and the disk mass than M bh, including with the velocity V max, which is closely related to the virial mass of the dark halo. On average, lenticular galaxies are characterized by higher massesM bh compared to other types of galaxies with similar characteristics. The dependence of the blackhole mass on the color index is bimodal: galaxies of the red group (red-sequence) with B-V >0.6–0.7 which are mostly early-type galaxies with weak star formation, differ appreciably from blue galaxies, which have higher values of M nc and M bh. At the dependences we consider between the masses of the central objects and the parameters of the host galaxies (except for the dependence of M bh on the central velocity dispersion), the red-group galaxies have systematically higher M bh values, even when the host-galaxy parameters are similar. In contrast, in the case of nuclear star clusters, the blue and red galaxies form unified sequences. The results agree with scenarios in which most red-group galaxies form as a result of the partial or complete loss of interstellar gas in a stage of high nuclear activity in galaxies whose central black-hole masses exceed 106−107 M ⊙ (depending on the mass of the galaxy itself). The bulk of disk galaxies with M bh > 107 M ⊙ are lenticular galaxies (types S0, E/S0) whose disks are practically devoid of gas.

Orbital-period variations in the eclipsing binary Y Cam

Abstract: We have studied the time behavior of the orbital period and the primary’s pulsation period for the eclipsing binary system Y Cam, whose secondary fills its Roche lobe and whose primary is a δ Scuti star. The times of minima available for this eclipsing binary cover 120 years. δ Scuti pulsations of the primary have been observed over the last 50 years, with the period of these pulsational brightness variations remaining virtually unchanged during the entire observed time interval. The large-amplitude cyclic variations of the orbital period of Y Cam cannot be explained solely by the presence of a third body in the system. It is possible to explain the period variations of Y Cam with magnetic oscillations or a superposition of a stationary matter flow from the lower-mass to the higher-mass component together with magnetic oscillations, similar to the case of AB Cas. A good agreement with observations is provided by a model assuming a stationary matter flow from the secondary filling its Roche lobe to the primary, at the rate of 2.85 × 10−7 M ⊙/year, superposed with irregular period jumps that can be explained by instabilities in the matter flow. We have detected cyclic variations of the orbital period of Y Cam with an amplitude of 0.011d, which can be understood if the binary moves in a long-period orbit (with a period of 38.6 years) around a third body with mass M 3 s> 0.30M ⊙. These cyclic period variations of the eclipsing binary agree with the observed small period variations of the δ Scuti pulsations.

The presence of a magnetic field on the pulsating subdwarf Balloon 090100001. Observations of 2012

Abstract: New polarization observations of the subdwarf Bal 09 are analyzed Bal 09 belongs to the group of hybrid sdB stars, which display both short- and long-period pulsations Explaining certain properties of Bal 09 that were previously unknown in relation to subdwarfs (variations of the amplitude of the fundamental pulsation mode, rotational splitting of line multiplets and variation of this splitting) requires invoking information about the magnetic field of the star According to estimates made in 2010, the longitudinal component of the magnetic field of Bal 09 is 34±63 G This value is significantly lower than the fields found earlier for six other hot subdwarfs New observational data for the longitudinal magnetic field of Bal 09 was obtained on July 27, 2012, using the main stellar spectrograph of the 6-m telescope of the Special Astrophysical Observatory (SAO) The longitudinal component of the magnetic field 〈B z 〉 was found via a regression analysis When applied to the star HD 210762 with a zero total magnetic field, this method yielded the value 〈B z 〉 = −12 ± 9 G The observations also included measurements of 〈B z 〉 for the well-studied magnetic star γ Equ, which is used at the SAO for calibration and testing of the polarimetric instruments The estimate obtained for γ Equ is 〈B z 〉 = −546±16G, consistentwith the general variations of the longitudinal magnetic-field component of this star This new study, based on data obtained on July 27, 2012, leads to a similar estimate of the longitudinal magnetic field, 〈B z 〉 = −23±53 G This estimate of 〈B z 〉 was obtained for the full analyzed spectral range (4400–4958 A) The corresponding “limited” solution yielded −32±63 G The regression analysis for the individual spectral sub-bands and for bands containing characteristic spectral features, did not provide firm evidence of the presence of a magnetic field, with a strength exceeding the error in 〈B z 〉 The data analysis leads to the conclusion that the errors of the measurements made in 2010 and 2012 are in good agreement This testifies to the reliability of the method applied and of the resulting observational material In addition, the estimates are in good agreement among themselves and with estimates obtained earlier, in 2010 The results unambiguously confirm the earlier conclusion that the subdwarf Bal 09 does not have magnetic field with a strength comparable to those detected earlier for six sdB and sdO stars Estimates of 〈B z 〉 for hot subdwarfs that have appeared in the literature since the 2010 study also provide trustworthy evidence for the absence of magnetic fields ∼ 1 kG in these objects

The character of solar-type activity and the depth of the convective zone

Abstract: The origin of solar-type activity for low-mass stars of late spectral types is considered. Spectroscopic data were used to study the dependence of the activity level logR′ HK on the lithium abundance logA(Li) and axial rotation rate. A close correlation between logA(Li) and logR′ HK is found for two groups of G stars, hotter and cooler than the Sun. This relation is most clearly expressed in the case of high activity, and is somewhat more strongly expressed for G6-K3 dwarfs, which includes many BY Dra variables, than for F8-G5 stars. It is confirmed that, for stars with high activity, both the lithium abundance and the activity level are determined by the rotation rate, which depends on the age. The lithium abundance exhibits different dependences on the chromospheric activity, depending on the level of this activity. Cooler stars, with detectable lithium and solar-like chromospheres, possess much stronger coronas. This change in the relationship between the relative luminosities of the chromosphere and corona can be reliably traced using larger datasets. The different ratios between the activity of the choromosphere and corona for cooler and hotter G stars may reflect the fact that their convective zones become deeper or shallower than some critical value. This is consistent with observations of parameters describing rotational modulation and the correlation and anti-correlation of chromospheric and photospheric activity indices for stars hotter and cooler than the Sun. Physically, this means that the character of the activity could be related to a changing contribution of the large-scale and local magnetic fields to the generation of the activity. The results of this study confirm the earlier idea that there may be different evolution paths associated with solar-type activity. The results can be used to refine methods for estimating ages of stars from their activity levels (gyrochronology).

Influence of the small-scale magnetic field on the evolution of the angle between the magnetic moment and rotation axis of radio pulsars with superfluid cores

Abstract: The evolution of the angle between the magnetic moment and rotation axis of radio pulsars (inclination angle) is considered taking into account the presence of a non-dipolar magnetic field at the neutron-star surface and superfluid neutrons in the stellar interior. It is assumed that the total loss of angular momentum by the pulsar can be represented as a sum of magnetodipole and current losses. The neutron star is treated as a two-component system consisting of a charged component (including protons and electrons, as well as the crust, which is rigidly coupled with them, and normal neutrons) and a superfluid core. The components interact through scattering of degenerate electrons on magnetized Feynman-Onsager vortices. If a superfluid core is absent, then, in spite of the presence of stable equilibrium inclination angles, the rate with which these are reached is so slow that most pulsars do not have sufficient time to approach them during their lifetimes. The presence of superfluid neutrons results, first, in faster evolution of the inclination angle and, second, in the final stage of the evolution being either an orthogonal or a coaxial state. The proposed model fits the observations better in the case of small superfluid cores.

Rotational-oscillatory variations in the Earth rotation parameters within short time intervals

Abstract: A mathematical model for rotational-oscillatory motions of the Earth is constructed by applying celestial mechanics to the spatial problem of the Earth-Moon system subject to the Sun’s gravitation. Some basic phenomena associated with tidal irregularity in the Earth’s axial rotation and the polar oscillations are studied. It is shown that the perturbing component of the gravitational-tidal forces orthogonal to the plane of the lunar orbit is responsible for some short-term perturbations in the Moon’s motion. The constructed model for the rotational-oscillatory motions of the deformable Earth includes both the main high-amplitude perturbations and more complex small-scale motions attributed to short-term lunar perturbations with combinational frequencies. Numerical modeling (interpolation and forecasting) of the Earth rotation parameters within various time intervals based on astrometric data obtained by the International Earth Rotation Service is presented.

The Lyapunov exponents in the dynamics of triple star systems

Abstract: The dynamics of weakly heirarchical triple stars with equal masses are considered Full spectra of the Lyapunov exponents are found via numerical integration of the orbits, for various initial configurations of the systemin the planar problem and with initial conditions in the vicinity of the 2 : 1 resonance (ie, with the initial ratios of the periods of the outer and inner binaries being close to 2 : 1) Dependences between the Lyapunov time and the disruption time of the systemare constructed for initial conditions near and far from resonance The character of these relationships is different near and far from resonance, corresponding to two kinds of Hamiltonian intermittency The trajectories “stick” to the regular component in phase space near resonance, while this effect is not dominant far from resonance Analysis of the distributions of the disruption times of the triple systems for initial conditions near and far from resonance confirm these conclusions

Parameters of the turbulence of the interplanetary plasma derived from scintillation observations of the quasars 3C 48 and 3C 298 at the solar-activity maximum

Abstract: An analysis of temporal spectra of interplanetary scintillations of the radio sources 3C 48 and 3C 298 observed at 111 MHz on the Big Scanning Antenna of the Lebedev Physical Institute at the maximum of the 24th solar-activity cycle is reported. The measured temporal spectra of the scintillations are used to estimate the velocity of the in homogeneities and the index of the spatial spectrum of the turbulence. The dependence of the spectral index of the turbulence on the solar-wind speed persists in periods of high solar activity, when the global spatial structure of the solar wind is strongly modulated by the activity cycle.