Accretion disks in AGN should be subject to the same disk instability responsible for dwarf novae outbursts and soft X-ray transients in cataclysmic variables (CVs) and LMXBs. It has been suggested that this thermal/viscous instability can account for long term variability of AGNs. We analyze here the application of the DIM to the AGN case, using our adaptive grid numerical code developed in the context of CVs, enabling us to fully resolve the disk radial structure. We show that in AGNs, the width of heating and cooling fronts is so small that they cannot be resolved by standard codes, and that they propagate on time scales much shorter than the viscous time. As a result, transition fronts propagate back and forth in the disk, leading only to small luminosity variations. Truncation of the inner part of the disk by e.g. an ADAF will not alter this result, but enables the presence of quiescent states.

We investigate the altitude dependence of hard X-ray (HXR) spectra in solar flares, i.e., whether the HXR spectra are related to the altitudes of reconnection sites. We assume that the reconnection altitude can be scaled by the distance between the two conjugate HXR footpoints in the flare. By searching the RHESSI flare list from 2002 to 2004, we find 42 solar flares below X-class that have enhanced 50–100 keV HXR emission and two well-resolved HXR footpoints at the nonthermal peak time. The preliminary results show that there is a weak correlation ($\sim$ –0.31) between the HXR spectral index and the HXR footpoint distance. We further discuss the possible implications.

We present a case study of “Khagol Mandal,” a voluntary organization primarily based in Mumbai, India. In the 20 years since its inception, Khagol Mandal has given more than 1000 public outreach programmes. The volunteers strive to go beyond amateur level by means of various study tours, astronomical experiments and workshops. These activities have inspired a number of students to take professional astronomy careers. With a volunteer force, probably largest in India or even south Asia, Khagol Mandal is well poised to take advantage of the archival data of large telescopes. With a little guidance from senior researchers, organizations like Khagol Mandal can provide a solution to the ever-increasing need for manpower for ancillary science from these large-scale facilities.

Planetary nebulae (PNe) in the Magellanic Clouds (LMC, SMC) offer a unique opportunity to study both the population and evolution of low- and intermediate-mass stars in an environment which is free of the distance scale bias that hinders Galactic PN studies. The emission shown by PNe in the 5–40 $\mu$m range is characterized by the presence of a combination of solid state features (from the dust grains) and nebular emission lines superimposed on a strong dust continuum. We acquired low resolution IRS spectroscopy of a selected sample of LMC and SMC PNe whose morphology, size, central star brightness, and chemical composition are known. The data have been acquired and reduced, and the IRS spectra show outstanding quality as well as very interesting features. The preliminary analysis presented here allows to determine strong correlations between gas and dust composition, and nebular morphology. More detailed analysis in the future will deepen our knowledge of the mass-loss mechanism, its efficiency, and its relation to PN morphology.

The modeling of the Asymptotic Giant Branch phase is made highly uncertain by some still unsolved issues related to the input macro-physics used to calculate the stellar evolution, namely mass loss, nuclear cross sections, overshooting and convective modeling. We show that in the massive intermediate mass models, which achieve at the bottom of their convective envelope temperatures sufficiently high to favour an advanced nucleosynthesis, the treatment of convection plays a major role in determining the physical and chemical evolution of the stellar models during this evolutionary phase.

A new theoretical calibration of surface-brightness fluctuations (SBF) for single age, single metallicity stellar populations is presented for the optical and near-IR broad-band filters, as well as for the HST WFPC2 filters. The IAC-star code is used together with two Padua and the Teramo stellar evolution libraries. A set of single-burst stellar populations with a wide range of ages (3Gy-15Gy) and metallicities (Z=0.0001-0.03) have been computed. The present theoretical calibration shows that the analysis of near-IR SBF provides a very powerful tool in the study and characterization of unresolved stellar populations.

Wide binaries, particularly in large numbers and as free from selection biases as possible, constitute a largely overlooked tool for studying the Galaxy. The goal of this review is to highlight the potential inherent to large samples of field wide binaries for research on problems as varied as star formation in the early Galaxy, the nature of halo dark matter, the evolution of the stellar halo, new geometric distances, metallicities, masses, and ages of field stars and white dwarfs, and much more. Using the Revised NLTT as an illustrative example, I review the main steps in the assembly of a large catalog of wide binaries useful for multiple applications. The capability of cleanly separating between the Galactic disk and halo populations using good colors and proper motions is emphasized. The critical role of large surveys for research on wide binaries as well as for the better understanding of the Galaxy in general is stressed throughout. Finally, I point out the potential for assembling new samples of wide binaries from available proper-motion surveys, and report on current efforts of using the SDSS towards this goal.

The predictions of the Padoan and Nordlund IMF model are tested using the largest simulations of supersonic hydrodynamic (HD) and magneto-hydrodynamic (MHD) turbulence to date (~10003 computational zones). The striking difference between the HD and MHD regimes, predicted by the model, is recovered.

We summarize recent numerical results on the control of the star formation efficiency (SFE), addressing the effects of turbulence and the magnetic field strength. In closed-box numerical simulations, the effect of the turbulent Mach number depends on whether the turbulence is driven or decaying: In driven regimes, increasing with all other parameters fixed decreases the SFE, while in decaying regimes the converse is true. The efficiencies in non-magnetic cases for realistic Mach numbers 10 are somewhat too high compared to observed values. Including the magnetic field can bring the SFE down to levels consistent with observations, but the intensity of the magnetic field necessary to accomplish this depends again on whether the turbulence is driven or decaying. In this kind of simulations, a lifetime of the molecular cloud (MC) needs to be assumed, being typically a few free-fall times. Further progress requires determining the true nature of the turbulence driving and the lifetimes of the clouds. Simulations of MC formation by large-scale compressions in the warm neutral medium (WNM) show that the generation of the clouds' initial turbulence is built into the accumulation process that forms them, and that the turbulence is driven for as long as accumulation process lasts, producing realistic velocity dispersions and also thermal pressures in excess of the mean WNM value. In simulations including self-gravity, but neglecting the magnetic field and stellar energy feedback, the clouds never reach an equilibrium state, but rather evolve secularly, increasing their mass and gravitational energy until they engage in generalized gravitational collapse. However, local collapse events begin midways through this process, and produce enough stellar objects to disperse the cloud or at least halt its collapse before the latter is completed. Simulations of this kind including the missing physical ingredients should contribute to a final resolution of the MC lifetime and the origin of the low SFE problems.

The properties of bright extragalactic planetary nebulae are reviewed based upon the results of low and high resolution spectroscopy. It is argued that bright extragalactic planetary nebulae from galaxies (or subsystems) with and without star formation have different distributions of central star temperature and ionization structure. As regards the chemical compositions, oxygen and neon are generally found to be unchanged as a result of the evolution of the stellar progenitors. Nitrogen enrichment may occur as a result of the evolution of the progenitors of bright planetary nebulae in all stellar populations, though this enrichment may be (more) random in old stellar populations. Helium abundances appear to be influenced by the chemical evolution of the host galaxy, with planetary nebulae in dwarf spheroidals having systematically elevated abundances. Neither the age nor the metallicity of the progenitor stellar population has a strong effect upon the kinematics observed for nebular shells. Both the range of expansion velocites, 8-28 km s$^{-1}$, and the typical expansion velocity, $\sim 18\,\mathrm{km\,s}^{-1}$, are found to be relatively constant in all galaxies. On the other hand, bright planetary nebulae in the bulge of M31 have systematically higher expansion velocities than their counterparts in M31's disk. The expansion velocities show no trend with nebular H$\beta$ luminosity, apart from a lack of large expansion velocities at the highest luminosities (the youngest objects), but appear to correlate with the $5007/\mathrm{H}\beta$ ratio, at least until this ratio saturates. These results suggest a link between the evolution of the nebular shells and central stars of bright extragalactic planetary nebulae.

Recently, high resolution observations by SOHO and TRACE spacecraft have identified oscillating loops and propagating waves in the solar coronal. These new discoveries established a new discipline that is known as coronal seismology. The importance of this lies in the potential for the diagnostics of coronal structures and knowledge of coronal heating. We present a study of the effects of radiative cooling and heating processes on longitudinal waves in coronal loops. We find that radiation and heating results in a clear modification in the evolution of temperature and pressure perturbations but in slight effect on the decay time of the wave.

We present the results of a case-study of three typical galaxies with integral-shaped warps. We apply a new method to directly fit tilted-ring models to high-quality Hi data cubes obtained with the WSRT and report on the features found to be present in the models.

I present a report of the work in progress towards building a graphical user interface (GUI) for STECKMAP (STEllar Content and Kinematics via Maximum A Posteriori). It is the first serious attempt at making a GUI for a software for analysis of stellar content from integrated spectra of galaxies. It will allow a wider fraction of the community to use this sort of tools thanks to improved user-friendliness. As a result, better understanding of these methods and their strengths and flaws will be achieved by the community. This software also has a strong pedagogical potential. It will contribute to a higher awareness of the community concerning the challenges and the oppportunities in stellar populations modelling. The homepage of the project is http://www.astro.u-strasbg.fr/Obs/GALAXIES/stecmap_eng.html.

It follows from the local mixing length theory that the convection in the atmospheres of yellow and red giants and super-giants become supersonic. In this work we studied the physical reality of such phenomenon and its possible consequences on the structure and evolution of stars involving such situations. The main conclusion is that the supersonic nature of convection as predicted by the local mixing length theory has been overestimated. If supersonic convection is not an artifact in all situations, it is the case at least for all yellow giants and super-giants. We believe that such an artifact is due to the imperfect of the mixing length theory. Owing to the fact that convective energy transport in the atmospheres of yellow giants and super-giants is quite negligible, these artifacts have very limited consequences on the structure and evolution of these stars. However, it is not the case for red giants and super-giants whose properties can be seriously affected by this overestimation. Our investigation shows that the theoretical red phases of stars under consideration are somewhat too blue as predicted with the usual mixing length theory. To this aim, full hydrodynamic simulation is needed in order to clear the doubts on the existence of supersonic convection in these red objects.

The main-belt asteroids are generally considered as the principal source for the near-Earth asteroids (NEAs). The ESA astrometric mission Gaia, due for launch in late 2011, will observe a very large number of asteroids (∼300,000 brighter than V = 20), the majority lying in the main-belt and with an unprecedented positional precision (at the sub-milliarcsecond level). Such high precision astrometry will enable to derive direct measures of the masses of the largest asteroids of which their precise determination will be of utmost significance for the knowledge of physical properties of asteroids. The method for computing the masses is based on the analysis of orbital perturbations during close encounters between massive asteroids (perturbers) and several smaller minor planets (targets). From given criteria of close approaches selection, we give the list of asteroids for which the mass can be determined, and the expected precision of these masses at mission completion.

We perform the two-dimensional radiation-hydrodynamic simulations to study the radiation pressure-dominated accretion flows around a black hole (BH). Our simulations show that the highly supercritical accretion flow (mass accretion rate is much larger than the critical value) is composed of the disk region and the outflow region above the disk.

The radiation force supports the thick disk and drives the outflow. The photon trapping plays an important role within the disk, reducing the disk luminosity. On the other hand, in the case that mass accretion rate moderately exceeds the critical value, we find that the disk is unstable and exhibits the limit-cycle oscillations. The disk oscillations in our simulations nicely fit to the variation amplitude and duration of quasi-periodic luminosity variations observed in the GRS 1915+105 microquasar.

We present a brief summary of Subaru observations of high-z galaxies. We discuss our future plan to probe galaxies beyond z = 10.

Since 1990, the United Nations has held an annual workshop on basic space science for the benefit of the worldwide development of astronomy. Additional to the scientific benefits of the workshops and the strengthening of international cooperation, the workshops lead to the establishment of astronomical telescope facilities through the Official Development Assistance (ODA) of Japan. Teaching material, hands-on astrophysics material, and variable star observing programmes had been developed for the operation of such astronomical telescope facilities in the university environment. This approach to astronomical telescope facility, observing programme, and teaching astronomy has become known as the basic space science TRIPOD concept. Currently, a similar TRIPOD concept is being developed for the International Heliophysical Year 2007, consisting of an instrument array, data taking and analysis, and teaching space science.

We discuss differences and similarities between jets powered by super-massive black holes in quasars and by stellar-mass black holes in microquasars. The comparison is based on multi-wavelength radio-to-infrared observations of the two active galactic nuclei 3C 273 and 3C 279, as well as the two galactic binaries GRS 1915+105 and Cyg X-3. The physical properties of the jet are derived by fitting the parameters of a shock-in-jet model simultaneously to all available observations. We show that the variable jet emission of galactic sources is, at least during some epochs, very similar to that of extragalactic jets. As for quasars, their observed variability pattern can be well reproduced by the emission of a series of self-similar shock waves propagating down the jet and producing synchrotron outbursts. This suggests that the physical properties of relativistic jets is independent of the mass of the black hole.