We present a time-series Doppler imaging study of the K-subgiant component in the RS CVn-type binary system IL Hya (Porb=12.905 d). From re-processing the unique long-term spectroscopic dataset of 70 days taken in 1996/97, we perform a thorough cross-correlation analysis to derive surface differential rotation. As a result we get solar-type differential rotation with a shear value α of 0.05, in agreement with preliminary suggestions from previous attempts. A possible surface pattern of meridional circulation is also detected.

Recently, the study of the influence of solar activity on the Earth's climate received strong attention, mainly due to the possibility, proposed by several authors, that global warming is not anthropogenic, but is due to an increase in solar activity. Although this possibility has been ruled out, there are strong evidences that solar variability has an influence on Earth's climate, in regional scales.

Here we review some of these evidences, focusing in a particular aspect of climate: atmospheric moisture and related quantities like precipitation. In particular, we studied the influence of activity on South American precipitations during centuries. First, we analyzed the stream flow of the Paraná and other rivers of the region, and found a very strong correlation with Sunspot Number in decadal time scales. We found a similar correlation between Sunspot Number and tree-ring chronologies, which allows us to extend our study to cover the last two centuries.

The 11-year cycle represents a simultaneous parallel change in both the activity level and the total irradiance of the Sun. So, in case of variations of the amplitude of the activity level - a power of a cycle - the amplitude of solar irradiance variations is expected to change correspondingly. The identical correlated course of the long-term variations of activity and luminosity of the Sun on the secular timescale has been observed earlier by Eddy (1976), and Borisenkov (1988). Moreover, according to the data of Borisenkov (1988), in each of 18 deep Maunder-type minima of solar activity, revealed over the span of the last 7500 years, the cooling of climate had been observed, while warming occurred during the periods of high maxima. Thus, the integral radiation has always been essentially higher at the maximum, and it had noticeably decreased at the minima. Therefore, quasi-periodic variations of the solar activity during both the 11-year cycle and 80- and 200-year cycles are accompanied by proportional variations of the integral flux of solar radiation, which result in geophysical effects. The main cause of climate change during the last millennia is the corresponding cyclic variation of the 80- and 200-year component of irradiance correlated with activity. That is why, the contemporary is not anomalous but is ordinary secular global warming (Aguilar 2003; Reid 2000), as well as previous similar cases of warming during the periods of secular activity growth is still mainly connected with an increase of the secular component of solar irradiance variation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The advantages of making astrometric observations from space are reviewed, and a project for measuring angular separations between stars along great circle arcs of the order of 90°, by means of a telescope mounted on a TD 1 satellite is described. Positions with accuracy of the order of ±0″.01, parallaxes to ±0″.007 and proper motions to ±0″.005 yr-1 for some 40000 stars brighter than 9m.5 would be obtainable in a two year programme.

We report on new B, V and I CCD photometry of the globular cluster M54 that was aimed at the study of its variable stars. With respect to the previous most recent work on M54 we have nearly doubled the number of detected variable stars: M54 can now be classified as intermediate in the Oosterhoff groups. The metallicity can be estimated for the cluster and field red giant stellar population, and for the variables.

I review the basic properties of low-luminosity active galactic nuclei (LLAGNs) — objects in which activity similar to, but intrinsically milder than, that in QSOs and luminous Seyferts is believed to be present. Until recently, most LLAGNs were first recognized as such and studied at optical wavelengths, but evidence for activity and valuable information concerning its nature are now also being obtained in many other spectral ranges. Low-ionization nuclear emission-line regions (LINERs) are the most common LLAGNs; in a large fraction of them the emission lines come from clouds of gas probably photoionized by a nonstellar continuum, rather than heated by shocks. It is also clear, however, that there could be substantial heterogeneity among LINERs, particularly those with extended emission; some may be produced by cooling flows, supernova-driven winds, and galaxy interactions or mergers. LLAGNs can easily be hidden from sight in a variety of ways, including obscuration by galactic or circumnuclear disks and dilution by bursts of star formation. Direct imaging, spectroscopy, and spectropolarimetry can be used to isolate the different components, especially with high spatial and/or spectral resolution. A surprising result is that Seyfert nuclei are sometimes found in dwarf and very late-type galaxies. The nearby Sd III-IV galaxy NGC 4395 contains the intrinsically faintest known Seyfert 1 nucleus, with a broad Ha luminosity only ∼ 0.1 that of M81. The idea that the apparent “activity” in some galaxies is a direct consequence of vigorous star formation has some strong supporting evidence, and should seriously be considered. As an example, I focus on the peculiar supernova 1987F, whose optical spectrum bears a striking resemblance to that of typical Seyfert 1 nuclei.

Based on detailed 2D radiation hydrodynamics (RHD) simulations, we have investigated the effects of photospheric temperature inhomogeneities induced by convection on spectroscopic determinations of the lithium abundance. Computations have been performed both for the solar case and for a metal-poor dwarf. NLTE effects are taken into account, using a five-level atomic model for Li I. Comparisons are presented with traditional 1D models having the same effective temperature and gravity. The net result is that, while LTE results differ dramatically between 1D and 2D models, especially in the metal-poor case, this does not remain true when NLTE effects are included: 1D/2D differences in the inferred NLTE Li abundance are always well below 0.1 dex. The present computations still assume LTE in the continuum. New computations removing this assumption are planned for the near future.

The study of fine structures in continuum radio emission from the sun is important to probe the physics of radio sources and of flares in particular. In this light the existing fine structure theories are reviewed and an application to a radio flare is given.

During this workshop, a considerable amount of data was presented, some refined versions of earlier results and some entirely new. While no completely definite picture of the local interstellar medium can be presented yet, some general conclusions can be drawn. We attempt to draw together the most relevant data in Section III. Some new UV results are collated with published results to help state the physical properties of the gas. A morphological view of the local medium is given in Section III. We confine ourselves to the region within 100 pc with the caveat that the distance of much of the material under discussion is poorly known.

Coronal mass ejections (CMEs) are an important aspect of coronal and interplanetary dynamics. They cause large geomagnetic storms and can drive transient interplanetary shocks, which in turn are a key source of energetic particle events. However, our knowledge of the origins and early development of CMEs at the Sun is limited. CMEs are most frequently associated with erupting prominences and long-enduring soft X-ray arcades, but sometimes with no observed surface activity. I review some of the well determined coronal properties of CMEs and what we know about their source regions, with emphasis on the characteristics of the associated prominences and helmet streamers. One of these characteristics is that many CMEs seem to arise from multipolar magnetic structures with multiple or kinked inversion lines. I also discuss the solar-cycle dependencies of these structures, including the role that erupting prominences and CMEs may play in the ejection of magnetic flux and helicity from the Sun.

To test the validity of the assumption of a ‘current-free’ magnetic field in the atmosphere above sunspots, we measured all three parameters of the magnetic field in an active region and compared it with the calculated current-free field according to the solution proposed by Schmidt. We found important differences between the calculated and the measured field.

We refer to an earlier paper where the objections to the ‘current-free field’ were that the calculated field has too simple a configuration to account for the fine structure observed in Hα and other solar observations.

After commenting on certain definitions related to both the terrestrial and celestial (quasi-inertial reference systems (CTS and CIS) to clarify terminology, the geodynamic requirements for such systems are reviewed. This is followed by a discussion of certain problematic aspects of the two systems. The article concludes with a list of required actions aimed to assure that the reference system issue is resolved early. The list is proposed for the joint IAG/IAU working group to be established in accordance with the Colloquium resolution printed elsewhere in this volume.

The observational evidence for dark halos around galaxies is shortly reviewed. New and old techniques and results constraining the mass, the distribution, the shape and the nature of dark halos are discussed.

Recent observations and models of solar prominences are reviewed. The observations suggest that prominences are located in or below magnetic flux ropes that lie horizontally above the PIL. However, the details of the magnetic structure are not yet fully understood. Gravity likely plays an important role in shaping the vertical structures observed in quiescent prominences. Preliminary results from a time-dependent model describing the interaction of a magnetic flux rope with photospheric magnetic elements are presented.

We consider rotating flows of an electrically conducting, viscous and resistive fluid in an external magnetic field with arbitrary combinations of axial and azimuthal components. Within the short-wavelength approximation, the local stability of the flow is studied with respect to perturbations of arbitrary azimuthal wavenumbers. In the limit of vanishing magnetic Prandtl number (Pm) we find that the maximum critical Rossby number (Ro) for the occurrence of the magnetorotational instability (MRI) is universally governed by the Liu limit ${\rm Ro}_{Liu}=2-2\sqrt{2}\approx -0.828$ which is below the value for Keplerian rotation RoKepler = −0.75.

We present a versatile method appropriate for the period analyses of observations containing phase information of all kinds of periodic or nearly periodic variable stars on the basis of phenomenological modelling of their phase curves and phase functions. The approach is based on rigorous application of a non-linear weighted least-squares method exploiting all available observational data and does not need an O-C diagram as an intermediate stage for period analyses. However, this approach enables us to determine precise times of extrema of light curves, to calculate ephemerides and construct plausible O-C diagrams. We substantiate the general applicability of the method on eclipsing binaries research.

Based on several tens of R0 measurements made during the past two decades, several studies have been performed to derive the best estimate of R0. Some used just simple averaging to derive a result, whereas others provided comprehensive analyses of possible errors in published results. In either case, detailed statistical analyses of data used were not performed. However, a computation of the best estimates of the Galactic rotation constants is not only an astronomical but also a metrological task. Here we perform an analysis of 53 R0 measurements (published in the past 20 years) to assess the consistency of the data. Our analysis shows that they are internally consistent. It is also shown that any trend in the R0 estimates from the last 20 years is statistically negligible, which renders the presence of a bandwagon effect doubtful. On the other hand, the formal errors in the published R0 estimates improve significantly with time.

A new class of planetary nebulae, in which abundances derived from optical recombination lines (ORL) seem to be much larger than those derived from collisionally excited lines (CEL) by up to one or two orders of magnitude is now well identified (Liu, these proceedings and references therein).

Photoionization models including two components, one highly enriched in C, N, O, Ne and deficient in H and the other one of more usual composition, can account for most of the numerous spectroscopic data available from UV to far-IR in two of the best observed, most extreme examples, namely NGC 6153 and M142 (Péquignot et aI., 2002, and in preparation). The few discrepancies left can generally be understood in terms of inaccuracy of the observations (calibration of infrared line fluxes relative to the optical) and some atomic data, particularly in the unusual conditions prevailing in the H-deficient component.

The problem of the cosmogony of the solar system has long occupied a central position in astronomical research. The origin of comets plays a substantial role in the solution to this problem. It is therefore necessary to study in detail the “original” and “future” orbits of the comets with nearly parabolic orbits and to examine in particular the great orbical changes that take place when comets pass within the spheres of action of the giant planets.

In the U S.S.R. — especially at the Institute for Theoretical Astronomy (I.T.A.) in Leningrad — considerable attention is paid to investigations of this type. In this respect it is useful to refer to IAU Symposium No. 45, organized in Leningrad in 1970, and in particular to the introductory report by Chebotarev (1972)

We present GalMC (Acquaviva et al. 2011), our publicly available Markov Chain Monte Carlo algorithm for SED fitting, show the results obtained for a stacked sample of Lyman Alpha Emitting galaxies at z ~ 3, and discuss the dependence of the inferred SED parameters on the assumptions made in modeling the stellar populations. We also introduce SpeedyMC, a version of GalMC based on interpolation of pre-computed template libraries. While the flexibility and number of SED fitting parameters is reduced with respect to GalMC, the average running time decreases by a factor of 20,000, enabling SED fitting of each galaxy in about one second on a 2.2GHz MacBook Pro laptop, and making SpeedyMC the ideal instrument to analyze data from large photometric galaxy surveys.