We present the results of global 3D MHD simulations of optically thin black hole accretion flows. The initial disk is embedded in a low density, spherical, isothermal halo and threaded by weak (β ≡ Pgas/Pmag = 100) toroidal magnetic field. General relativistic effects are simulated by using the pseudo-Newtonian potential. When the Maxwell stress in the innermost region of the disk is reduced due to the loss of magnetic flux or by decrease of disk temperature, inner torus is created around 4 – 10rs. We found that in such an inner torus, one-armed (m = 1) density enhancement grows and that the inner torus oscillates quasi-periodically. The oscillation period is about 0.1s when we assume a 10M⊙ black hole. This frequency agrees with the low-frequency QPOs observed in low/hard state of black hole candidates. The disk ejects winds whose opening angle is about 30 degree. The maximum velocity of the wind is about 0.05c.

Recent X-ray observations of microquasars and Seyfert galaxies reveal broad emission lines in their spectra, which can arise in the innermost parts of accretion disks. Recently Müller & Camenzind (2004) classified different types of spectral line shapes and described their origin. Zakharov (2006b) clarified their conclusions about an origin of doubled peaked and double horned line shapes in the framework of a radiating annulus model and discussed s possibility to evaluate black hole parameters analyzing spectral line shapes.

Our goal is to study relatively quiescent dense gas cores, isolated from disruptive stars, to understand the initial conditions of massive star formation. Determining their mass, size, dynamical status, and core mass distribution is a starting point to understand the mechanisms for formation, collapse, and the origin of their IMF. We obtained CSO 350 μm, images of quiescent regions in Orion and detected 51 resolved or nearly resolved molecular cores with masses ranging from 0.1 M to 46 M (Li et al. 2006). The mean mass is 9.8 M, which is one order of magnitude higher than that of the resolved cores in low mass star forming regions, such as Taurus. Our sample includes largely thermally unstable cores, which implies that the cores are supported neither by thermal pressure nor by turbulence, and are probably supercritical. They are likely precursors of protostars.

Many fundamental problems in optical astronomy – from planetary science, galactic structure, optical transients, to large-scale structure and cosmology – could be addressed though the same data set with millions of exposures in superb seeing, in multiple passbands, to very faint magnitudes over a large area of sky. This capability is largely driven by technology. In a logical progression towards this scientific capability, several increasingly ambitious wide-field optical surveys are planned in the next few years. A uniform high quality database covering all these science areas would be an ideal match to the VO. The above utopian goal of simultaneous pursuit of parallel surveys is achievable, but it relies on the ability to image a wide field quickly and deeply, and it is a non-linear function of the camera+telescope étendue.

Black hole masses in Active Galactic Nuclei have been determined in 35 objects through reverberation mapping of the emission line region. I mention some uncertainties of the method, such as the “scale factor” relating the Virial Product to the mass, which depends on the unknown structure and dynamics of the Broad Line Region.

When the black hole masses are estimated indirectly using the empirical size-luminosity relation deduced from this method, the uncertainties can be larger, especially when the relation is extrapolated to high and low masses and/or luminosities. In particular they lead to Eddington ratiosof the order of unity in samples of Narrow Line Seyfert 1. As the optical-UV luminosity is provided by the accretion disk, the accretion rates can be determined and are found to be much larger than the Eddington rates.

So, accretion must be performed at a super-critical rate through a slim disk, resulting in rapid growth of the black holes. The alternative is that the mass determination is wrong at this limit.

We present causal and positional evidence of triggered star formation in bright-rimmed clouds in OB associations, e.g., Ori OB1, and Lac OB1, by photoionization. The triggering process is seen also on a much larger scale in the Orion-Monoceros Complex by the Orion-Eridanus Superbubble. We also show how the positioning of young stellar groups surrounding the H II region associated with Trumpler 16 in Carina Nebula supports the triggering process of star formation by the collect-and-collapse scenario.

Astrophysical particle acceleration involves the efficient conversion of bulk energy to individual charge particle energy through work done by electric field. The ways in which this happens are quite varied but when considered from a physics perspective, commonalities can found between acceleration in quite different sites.

We show that the detection of double-barred (S2B) galaxies beyond the nearby universe is possible out to redshifts 0.1 ≲ z ≲ 0.5 with the resolution of the HST Advanced Camera for Surveys. We present the most distant S2B currently known, at z = 0.148.

The term ‘grid’, in the Virtual Observatory (VO) context, has mainly been used to indicate a set of interoperable services, allowing transparent access to a set of geographically distributed and heterogeneous archives and catalogues, data exchange and analysis, etc. The design of the VO has been however mainly geared at allowing users to access registered services.

Contemporary information on the nature of the circumstellar environment in early-type interacting binaries derived from observation is discussed. Emphasis is placed on results from FUV spectroscopy. New spectra from the FUSE spacecraft and earlier FUV observations with IUE have revealed the presence of hot interaction regions, bipolar outflows, splash outflows, and accretion hot spots in Algol-type systems with B-type mass gainers. In addition, close O-type pairs and systems containing O + W stars show a shock-heated region generated from their colliding winds. Recent FUSE observations of an apparent hot accretion spot and associated splash plasma in the direct-impact system U Cephei are presented.

Merger theory, in its extreme form, postulates that ellipticals are the products of mergers of spirals. While the morphology-clustercentric relationship (Whitmore et al., 1993), indicates that the morphological fractions are unaffected by the local properties of the clusters, considerable observational evidence has surfaced in favor of the existence of marginally bound pairs; that are the source of the most frequent collisions (Chengalur et al., 1996 and references therein). To test the global impact of galaxy collisions on their evolution we have studied many collisions between spirals and ellipticals, as well as spiral and elliptical pairs. The details of the models and methods are in Chatterjee & Magalinsky, 2002; and we refer to it. Marginally bound, eccentric orbits are found to maintain their eccentricities for a long time; which is supported by analytical research (Magalinsky & Chatterjee, 2000). The calculation of collision frequency indicates that only of the order of 5% of ellipticals can be formed in this way. A remarkable phenomenon is that the fraction of blue galaxies around z = 0.3 to 0.5 is more than in the present epoch – the B-O effect (Butcher & Oemler, 1978). While observations indicate that the effect is primarily due to an increase in galaxies with perturbed morphology (e.g., Faber et al., 1995), in the same environment we find a homogeneous population of normal red galaxies, that have almost finished their star formation.

We study the possibility of pure general relativistic models without exotic matter to describe the observed flattening of the rotation curves for stars moving in circular orbits in a galaxy disk. In particular we consider the dragging of inertial frames (rotation of the source) and the presence of a Taub–NUT (Newman–Unti–Tamburino) “charge”, the gravitational equivalent to a magnetic monopole in electrodynamics.

We report time-resolved V- and R-band CCD photometry of the eclipsing binary RZ Cas obtained with 38-cm Cassegrain telescope at the Crimean Astrophysical Observatory during July 2004 – October 2005. The obtained lightcurves clearly demonstrates rapid pulsations with a period of about 22 min. A periodogram analysis of these oscillations is also reported. On 12 January, 2005 (JD 2453383) we observed rapid variability with higher amplitude (∼0m.1), that perhaps may be interpreted as a high-mass-transfer-rate event and inhomogeneity of the accretion stream. Follow-up observations (both photometric and spectroscopic) of RZ Cas are strictly desirable for more detailed study of such events.

Our model for global circulations in the solar convective zone leads to an equatorial drift at its base with an amplitude of about 7 m/s. Its penetration into the solar tachocline is too weak to play any role in the solar dynamo. It confines, however, the internal magnetic decay modes to the radiative core so that the tachocline can be explained as a magnetic Hartmann layer. In the tachocline for the toroidal fields the magnetic Tayler instability exists. We found stability limits for toroidal fields of only 100 G.

We revisit the complex structure of the A85-A87 cluster, based on a volume complete VLA-HI imaging survey, as well as optical photometry and spectroscopy. HI imaging studies of a few nearby clusters have shown that most of the HI rich galaxies around clusters are located within infalling groups. The case of A 85 is a very peculiar one, with all the 11 HI-detected galaxies projected east of A 85, and all but one with much lower radial velocities (~ 15,000 km s−1 than the cluster's systemic velocity (16,500 km s−1) In order to quantify the degree of substructure in A 85 we estimate the parameter δ defined by Dressler and Schectman, and plot it in Fig. 1a: many large circles in the same area indicate a great possibility of substructuring (Bravo-Alfaro et al. 2007 in prep).

Over twenty five years of X-ray observations of the Seyfert 1.9 galaxy NGC 2992 show that it is a promising test-bed for severely constraining accretion disk models. The previous interpretation of the historical activity of NGC 2992 in terms of the accretion disk slowly becoming dormant over many years and then ‘re-building’ itself is not supported by new data. A recent year-long monitoring campaign with RXTE showed that the X-ray continuum varied by more than an order of magnitude on a timescale of weeks. During the large-amplitude flares the centroid energy of the Fe K emission-line complex became significantly redshifted, indicating that the violent activity was occurring close to the putative central black hole where gravitational energy shifts can be sufficiently large. For the continuum, the Compton-y parameter remains roughly constant despite the large-amplitude luminosity variability, with (kT) τ ∼ 20–50.

Joint Discussion 14 was held at the General Assembly of the International Astronomical Union from August 17 until 23 in the beautiful Bohemian capital, Prague. The blueprints for this meeting were laid out during the MODEST-5 workshop, held in the Canadian city of Hamilton, Ontario in August 2004. We were sitting in a nice cafe with local brew and food, discussing the future of the MODEST community when we posed the idea for this Joint Discussion at the General Assembly. The meeting was then coined MODEST-7.

I'll describe the current status of the GRAPE-DR project. The GRAPE-DR is the next-generation hardware for N-body simulation. Unlike the previous GRAPE hardwares, it is programmable SIMD machine with a large number of simple processors integrated into a single chip. The GRAPE-DR chip consists of 512 simple processors and operates at the clock speed of 500 MHz, delivering the theoretical peak speed of 512/226 Gflops (single/double precision). As of August 2006, the first prototype board with the sample chip successfully passed the test we prepared. The full GRAPE-DR system will consist of 4096 chips, reaching the theoretical peak speed of 2 Pflops.

We present results from a project aimed at better understanding the kinematics and metallicities of populous clusters in the LMC. In an effort to update previous [Fe/H] determinations, we have utilized FORS2 on the VLT to obtain infrared spectra for more than 200 stars in 28 LMC clusters. The absorption lines of the calcium II triplet were then used to calculate radial velocities and [Fe/H] for a sample of clusters spanning a large range of ages (~ 1-13 Gyr) and metallicities (−0.3 >[Fe/H]> − 2.0). We determine mean cluster velocities to typically 1.6 km s−1 and mean metallicities to 0.04 dex (random error). For eight of these clusters, we report the first spectroscopically determined metallicities based on individual cluster stars, and six of these eight have no published radial velocity measurements. Combining our data with archival HST/WFPC2 photometry, we find the newly measured cluster, NGC 1718, is one of the most metal-poor ([Fe/H] ~ −0.80), intermediate age (~ 2 Gyr) inner disk clusters in the LMC. Similar to what was found by previous authors, this cluster sample has motions consistent with that of a single rotating disk system, with no indication that the newly reported clusters exhibit halo kinematics. Additionally, our findings confirm previous results which show that the LMC lacks the metallicity gradient typically seen in non-barred spiral galaxies, suggesting that the bar is driving the mixing of stellar populations in the LMC. However, in contrast to previous work, we find that the higher metallicity clusters (≥−1.0 dex) in our sample show a very tight distribution (mean [Fe/H] = −0.48, σ = 0.09), with no tail toward solar metallicities. The cluster distribution is similar to what has been found for red giant stars in the bar, which indicates that the bar and the intermediate age clusters have similar star formation histories. This is in good agreement with recent theoretical models that suggest the bar and intermediate age clusters formed as a result of a close encounter with the SMC ~ 4 Gyr ago.

We present the results of observations of distant galaxies (z ~ 0.8) at high spatial resolution (~0.1"). We observed 7 fields of 1' × 1' with the NACO Adaptive Optics system (VLT) in Ks (2.2μm) band with typical V ~ 14 guide stars and 3h integration time per field. Observed fields are selected within the COSMOS survey area. We analyze the morphologies by means of B/D (Bulge/Disk) decomposition with GIM2D and CAS (Concentration-Asymmetry) estimators for 79 galaxies with magnitudes between Ks = 17 − 23 and classify them in three main morphological types (Late Type, Early Type and Irregulars). We obtain for the first time an estimate of the distribution of galaxy types at redshift z ~ 1 as measured from the near infrared at high spatial resolution.