The observational data of the Orion Nebula Cluster (ONC) is reanalyzed by means of new sets of pre-main sequence (PMS) evolutionary tracks including rotation, non-gray boundary conditions (BC's) and either low (LCE) or high convection efficiency (HCE), aiming better understanding of the appropriate physical constraints for the rotational evolution of the stars within the ONC. The role played by convection is a key aspect of our analysis, since there are conflicting results from theory and observations. We derived stellar masses and ages for the ONC by using both LCE and HCE and considered was the role of non-gray atmospheres. Our results show that the resulting mass distribution for the bulk of the ONC population is in the range 0.2-0.4M⊙ for our non-gray models, and in the range 0.1-0.3M⊙ for gray models. In agreement with previous works, we found that a large percentage (∼70%) of low-mass stars (M≤Mtr, where Mtr is a transition mass) in the ONC appears to be fast rotators (P<4days). Mtr depends on the model choosen, being Mtr=0.5 for LCE, Mtr=0.35 for HCE and, as found in previous works, Mtr=0.25 for gray models. Finally, our analysis indicates that a second parameter is needed for a proper description of convection in the PMS phase.

Two distinct frequencies are often present in frequency power spectra of low-mass X-ray binary lightcurves. These frequencies are closely related to each other and there is a strong evidence that they have origin in the orbital motion in an accretion disc. A mechanism has to be in act that provides a modulation of emergent flux at observed frequencies – not necessarily the actual frequencies at which the fluid oscillates. Using numerical ray-tracing we show that strong gravity has an effect on light modulation and may itself be responsible for significant part of variations in observed lightcurves.

Planetary nebulae (PN) are favourite objects in the study of stellar populations both in the Galaxy and in other objects as well, due to their high brightness and the considerable range in their kinematic properties and chemical composition. In this work, we take into account available data samples of PN in Local Group galaxies and compare the derived information from different objects, particularly regarding their chemical composition, space distribution, kinematics, and the PN luminosity function.

The frequency distribution f(a) of semimajor axes of double and multiple systems, and their eccentricities and mass ratios, contain valuable fossil information about the process of star formation and the dynamical history of the systems. In order to advance in the understanding of these questions, we made an extensive analysis of the frequency distribution f(a) for wide binaries (a > 25 AU) in various published catalogues, as well as in our own (Poveda et al 1994; Allen et al 2000; (Poveda & Hernández–Alcántara 2003). Based upon all these studies we have established that the frequency distribution f(a) is a function of the age of the system and follows Öpik's distribution f(a) ∼ 1/a in the range of 100 AU < a < ac(t), where ac (t) are the critical semimajor axes beyond which binaries have been dissociated by encounters with massive objects. We argue that the physics behind the distribution f(a) ∼ 1/a is a process of energy relaxation, analogous to those present in stellar clusters (secular relaxation) or in the early stages of spherical galaxies (violent relaxation). The existence of runaway stars indicates that both types of relaxation are important in the process of binary and multiple star dynamical evolution.

Observations of molecular gas at 7 mm are made with the Green Bank Telescope (GBT) in a sample of planetary nebulae (PNe). PNe were selected to test stellar evolution models that include extra mixing processes induced by rotation by directly measuring the isotopic abundance ratios of processed material that has escaped the progenitor star. Moreover, these data are used to probe theories of chemical evolution through a sample of AGB stars, protoplanetary nebulae, and young and evolved PNe. One goal is to constrain the timelines and list of tracers for studying the molecular emission in these sources and examine the role of clumping for different species.

Using the spectral fitting technique we have studied the components contributing to the soft X-ray spectra of four AGN. The selected objects are the Seyfert 1 galaxies: HE 1143-1810, Mkn 110, CTS A08.12 and ESO 359-G19. The high-resolution X-ray spectra analysed were taken with the Reflection Grating Spectrometers on board the XMM-Newton satellite. In contrast to the results for other well-studied Seyfert 1 galaxies, we have found that the spectra of the four galaxies lack of significant absorption features. Hence, there are no signs of high-column-density partially-ionised absorbing material in the vicinity of the active nucleus in these galaxies.

Over the last five years, enormous progress in accurate distance measurements for nearby galaxies has been attained. The Hubble Space Telescope allows us to estimate distances of about 7–10% accuracy using red giant branch (RGB) up to 8 Mpc. Now we have very accurate distances for more than 200 galaxies within ~6 Mpc.

We present results from a series of projects aimed at better understanding the ages, velocities, metallicities, and distances of populous clusters in the LMC. Using FORS2 on the VLT, we obtained near-infrared spectra for more than 200 stars in 28 LMC clusters, which span a large range of ages and metallicities. The strong absorption lines of the Ca II triplet are used to calculate cluster velocities and abundances. We determine cluster ages through main sequence fitting of theoretical isochrones to deep optical photometry using a combination of published photometry, VLT FORS2 images and archival HST WFPC2 images. As shown by Grocholski & Sarajedini, a cluster's age and [Fe/H] can be used to predict the K-band luminosity of core helium burning red clump (RC) stars in that cluster. Using ISPI on the CTIO 4m telescope, we imaged 17 LMC clusters in the J– and K–bands, with the resulting photometry reaching ∼0.5 mag below the RC. We combine the measured apparent RC magnitudes with the predicted absolute values to determine absolute distances to each of these clusters and thereby probe the structure of the LMC as traced by its intermediate-age clusters.

We present NIR spectroscopy of emission lines of a sample of five z≃6 quasars, including fainter objects than observed before. The measured FeII/MgII ratios are around solar and consistent with a lack of evolution of the metallicity of quasar BLRs up to z≃6, suggesting that stars in their hosts formed at z≫6. The BH masses, measured from both MgII and CIV line widths are within the range 2-16×108M⊙, the smallest found in such distant objects.

The non-local, time-dependent convection theory of Kuhfuß (1986) in both its one- and three-equation form has been implemented in the Garching stellar evolution code. We present details of the implementation and the difficulties encountered. Specific test cases have been calculated, among them a 5 M⊙ star and the Sun. These cases point out deficits of the theory. In particular, the assumption of an isotropic velocity field leads to too extensive overshooting and has to be modified at convective boundaries. Some encouraging aspects are indicated as well.

H I 21cm-line self-absorption (HISA) reveals the shape and distribution of cold atomic clouds in the Galactic disk. Many of these clouds lack corresponding CO emission, despite being colder than purely atomic gas in equilibrium models. HISA requires background line emission at the same velocity, hence mechanisms that can produce such backgrounds. Weak, small-scale, and widespread absorption is likely to arise from turbulent eddies, while strong, large-scale absorption appears organized in cloud complexes along spiral arm shocks. In the latter, the gas may be evolving from an atomic to a molecular state prior to star formation, which would account for the incomplete HISA-CO agreement.

The manuscript presents a review of the results obtained by the author from fast sequential H-alpha filtergrams taken for a quiescent filament together with similar results of other authors. The revealed structure clearly shows that the foot elements of the filament are surrounded by a fishbone-like plage area (magnetic region). Some parts of the filament exist at the boundary of large supergranular cells of about 40′′ in diameter. It seems that the filament is formed due to mixing of magnetic elements of different polarities.

I will describe recent results on constructing samples of candidate active galactic nuclei (AGN) at or beyond redshift 7, probing several orders of magnitude fainter than the top end of the quasar luminosity function at redshift 6. These advances have been made possible by the advent of deep, wide multi-waveband surveys that enable the selection of samples of sources that are detected at radio or X-ray wavelengths but completely undetected at optical wavelengths to very deep limits. A variety of multi-band selection criteria are used to identify the high-redshift candidates and eliminate lower-redshift interlopers by means of extensive spectral energy distribution modelling. The resulting constraints on the numbers of high-redshift AGN at or above redshift 7 are used to examine the evolution of the AGN luminosity function at high redshift, and help understand the properties of the first supermassive black holes in the universe.

Surrounding the Galactic center is a molecular cloud with a central black hole. This raises the question as to how the hole was formed. While clouds containing HCN are circulating around the Galactic center, they do not all move at the same speed and so collide mutually and should make a more uniform motion and distribution after a period of some 100 kyrs (e.g., Ekers, van Gorkom, Schwartz et al. 1983). Hence some very energetic phenomena must have occurred within that period.

Metal-rich globular clusters are important to study the chemical evolution of the Galaxy and one of the best approaches to better understand the physical processes occurring in stellar populations as building blocks of galaxies. We report on Mn, Cu, and Zn abundances of giant stars in metal-rich Galactic globular clusters (−0.70 < [Fe/H] < −0.11), measured on spectra obtained with the UVES spectrograph on the 8-m VLT UT2-Kueyen telescope.

We present the high-resolution 12CO(J = 1 − 0), 13CO(J = 1 − 0) and 12CO(J = 3 − 2) maps toward a GMA located on the southern arm region of M31 using Nobeyama 45 m and ASTE 10 m telescopes. The GMA consists of two velocity-components, i.e., red and blue. The blue component shows a strong and narrow peak, whereas the red one shows a weak and broad profile. The red component has a lower 12CO(J = 1 − 0)/13CO(J = 1 − 0) ratio (~ 5) than that of the blue one (~ 16), indicating that the red component is denser than the blue one. The red component could be the decelerated gas if we consider the galactic rotational velocity in this region. We suggest that the red component is “post shock” dense gas decelerated due to a spiral density wave. This could be observational evidence of dense molecular gas formation due to galactic shock by spiral density waves.

We also present results from on-going observations toward NGC 604, which is the supergiant HII region of M33, using Nobeyama 45 m and ASTE 10 m telescopes. The ratio of 12CO(J = 3 − 2) to 12CO(J = 1 − 0) ranges from 0.3 to 1.2 in NGC 604. The 12CO(J = 1 − 0) map shows the clumpy structure while 12CO(J = 3 − 2) shows a strong peak near to the central star cluster of NGC 604. The high ratio gas is distributed on the arc-like or shell-like structure along with Hα emission and HII region detected by radio continuum. These suggest that the dense gas formation and second generation star formation occur in the surrounding gas compressed by the stellar wind and/or supernova in central star cluster.

We have acquired high spectral resolution observations (R=150,000) of the planetary nebulae NGC 7009 and NGC 6153, using bHROS on Gemini South. Observations of this type may provide a key to understanding why optical recombination lines (ORLs) yield systematically higher heavy element abundances for photoionized nebulae than do the classical forbidden collisionally excited lines (CELs) emitted by the same ions; NGC 7009 and NGC 6153 have notably high ORL/CEL abundance discrepancy factors (ADFs) of 5 and 10, respectively. Due to the opposite temperature dependences of ORLs and CELs, ORLs should be preferentially emitted by colder plasma. Our bHROS observations of NGC 7009 reveal that the [O III] 4363 Å CEL has a FWHM linewidth that is 1.5 times larger than that shown by O II ORLs in the same spectrum, despite the fact that all of these lines are emitted by the O$^{2+}$ ion. The bHROS spectra of NGC 6153 also show that its O II ORLs have significantly narrower linewidths than do the [O III] 4363 Å and 5007 Å lines but, in addition, the [O III] 4363 Å and 5007 Å lines show very different velocity profiles, implying the presence of large temperature variations in the nebula.

The European Grid of Solar Observations (EGSO) is a Solar virtual observatory (see Hill et al., 2002). It has been funded through the 5th Framework Program of the European Community. A dozen of laboratories, mixing Solar Physics and Information Technology, in Great Britain, France, Italy and Swiss have been involved in this project during 3 years. A grid accessing several dozens of databases and archives scattered all around the world has been developped as well as a Solar Event Catalogue and a Solar Feature Catalogue. The original aspect of this work consists in the possibility not only to search through the characteristics of observations, but also search for available data corresponding to specific kinds of events. So it is now very important to be able to follow the Sun 24 hours a day in order to enrich the events database for future queries. More informations on EGSO, catalogues and user interface can be accessd through the web site: http://www.egso.org/

Using a semiconvective model based on thermohaline convection, we investigate the case of an expanding core of a main-sequence massive star. The numerical simulations at high Prandtl number show a flow consistent with the assumption that a dynamically neutral layer sits between the core and the radiative envelope. More simulations at low Prandtl number are needed to infer scaling laws applicable to astrophysical regimes.