We estimate the consequences of a potential strong decrease of the solar activity using the model simulations of the future driven by pure anthropogenic forcing as well as its combination with different solar activity related factors: total solar irradiance, spectral solar irradiance, energetic electron precipitation, solar protons and galactic cosmic rays. The comparison of the model simulations shows that introduced strong decrease of solar activity can lead to some delay of the ozone recovery and partially compensate greenhouse warming acting in the direction opposite to anthropogenic effects. The model results also show that all considered solar forcings are important in different atmospheric layers and geographical regions. However, in the global scale the solar irradiance variability can be considered as the most important solar forcing. The obtained results constitute probably the upper limit of the possible solar influence. Development of the better constrained set of future solar forcings is necessary to address the problem of future climate and ozone layer with more confidence.

We review a slightly modified method of eclipse mapping, applicable to mode identification in eclipsing binaries containing a pulsating component. The observed light curve is used by the procedure without removing from it the badly determined eclipsing part.

The circumstellar gas/dust envelopes of stars on and beyond the asymptotic giant branch harbor an impressive number of different molecular species and their isotopic variants. Some of these molecules are of photospheric origin, but the majority have been produced through various chemical processes in the envelope. This chemistry depends primarily on the chemical composition of the gas (i.e., C/O<1 or >1), but the conditions also change as the central star evolves. In this review we present circumstellar molecular abundance and isotope ratio estimates, and discuss how they can be used in the study of the late evolution of stars, which in extreme cases may become heavily obscured.

During their main sequence evolution, massive stars can develop convective regions very close to their surface. These regions are caused by an opacity peak associated with iron ionization. Cantiello et al. (2009) found a possible connection between the presence of sub-photospheric convective motions and small scale stochastic velocities in the photosphere of early-type stars. This supports a physical mechanism where microturbulence is caused by waves that are triggered by subsurface convection zones. They further suggest that clumping in the inner parts of the winds of OB stars could be related to subsurface convection, and that the convective layers may also be responsible for stochastic excitation of non-radial pulsations. Furthermore, magnetic fields produced in the iron convection zone could appear at the surface of such massive stars. Therefore subsurface convection could be responsible for the occurrence of observable phenomena such as line profile variability and discrete absorption components. These phenomena have been observed for decades, but still evade a clear theoretical explanation. Here we present preliminary results from 3D MHD simulations of such subsurface convection.

At the beginning of the 20th century, the development of radio time signals offered the possibility of unifying the measurements of Universal Time (UT). A new service, the Bureau International de l’Heure, hosted by the Paris Observatory, was entrusted with this task. The BIH began its operation in 1912, although its statutes were officially settled only in 1919. This paper recalls the activities of the BIH on time determination and various connected fields: Earth rotation, reference frames, atomic time. With the importance of atomic time and the emergence of new techniques for the measurement of Earth rotation, a new organization was required. It was prepared by the MERIT and COTES programs (1978) and by the bodies of the Metre Convention, with the active participation of the BIH. The BIH was dissolved at the end of 1987, its work being shared between the Bureau International des Poids et Mesures and the new International Earth Rotation Service.

Comets are believed to be the most pristine material surviving from the origin of the Solar System. The nature of their volatiles should in principle provide chemical and physical clues to their formation environment in the solar nebula. Another important aspect of the study of comets is the extent to which they may incorporate relatively unprocessed interstellar material.

Our knowledge of the composition of cometary ices has been greatly improved in this last decade. The years 1995-1996 were rich in new results, with the close approach to Earth of comet C/1996 B2 Hyakutake and the discovery of the bright comet C/1995 O1 Hale-Bopp at large heliocentric distance. We will present the current knowledge of the nature and abundances of cometary volatiles and mention some of the outstanding issues related to the origin of comets and their links to interstellar material.

The prototype telescope and instruments for the Stellar Observations Network Group (SONG) are nearing completion at the Observatorio del Teide on Tenerife. In this contribution we describe the current status (autumn 2013) of the telescope and its instrumentation. Preliminary performance characteristics are presented for the high-resolution spectrograph based on daytime observations of the Sun and a 4 hour test series obtained for the sub-giant β Aquilae.

HAT-South is a network of six identical, fully automated wide field telescopes, to be located at three sites (Chile: Las Campanas, Australia: Siding Springs, and Namibia: HESS site) in the Southern hemisphere. The primary purpose of the network is to detect and characterize a large number of extra-solar planets transiting nearby bright stars, and to explore their diversity. Operation of HAT-South is a collaboration among the Harvard-Smithsonian Center for Astrophysics (CfA), Max Planck Institute for Astronomy (MPIA) and the Australian National University (ANU). The network is expected to be ready for initial science operations in 2009. The three sites will permit near round-the-clock monitoring of selected fields, and the continuous data-stream will greatly enhance recovery of transits. HAT-South will be sensitive to planetary transits down to R≈14 across a 128 square-degrees combined field of view, thereby targeting a large number of dwarfs with feasible confirmation-mode follow-up. We anticipate a yearly detection rate of approximately 25 planets transiting bright stars.

Solar coronal dimmings have been observed extensively in the past two decades and are believed to have close association with coronal mass ejections (CMEs). Recent study found that coronal dimming is the only signature that could differentiate powerful flares that have CMEs from those that do not. Therefore, dimming might be one of the best candidates to observe the stellar CMEs on distant Sun-like stars. In this study, we investigate the possibility of using coronal dimming as a proxy to diagnose stellar CMEs. By simulating a realistic solar CME event and corresponding coronal dimming using a global magnetohydrodynamics model (AWSoM: Alfvén-wave Solar Model), we first demonstrate the capability of the model to reproduce solar observations. We then extend the model for simulating stellar CMEs by modifying the input magnetic flux density as well as the initial magnetic energy of the CME flux rope. Our result suggests that with improved instrument sensitivity, it is possible to detect the coronal dimming signals induced by the stellar CMEs.

The current version of the IAU Meteor Data Centre catalogue of photographic orbits comprising the orbital and geophysical data of 4581 meteors is applied for a more representative search of the mean orbits of bolide meteor streams among photographic meteors. We have made the search based on a computerized stream search procedure utilizing the Southworth-Hawkins D-criterion. The results are compared with the previous similar analysis made by Porubčan & Gavajdová (1994).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

LOFAR (Low Frequency Array) is an innovative radio telescope optimized for the frequency range 30–240 MHz. The telescope is realized as a phased aperture array without any moving parts. Digital beam forming allows the telescope to point to any part of the sky within a second. Transient buffering makes retrospective imaging of explosive short-term events possible. The scientific focus of LOFAR will initially be on four key science projects (KSPs): (i) Detection of the formation of the very first stars and galaxies in the universe during the so-called epoch of reionization by measuring the power spectrum of the neutral hydrogen 21-cm line (Shaver et al. 1999) on the ∼ 5′ scale; (ii) Low-frequency surveys of the sky with of order 108 expected new sources; (iii) All-sky monitoring and detection of transient radio sources such as γ-ray bursts, X-ray binaries, and exo-planets (Farrell et al. 2004); and (iv) Radio detection of ultra-high energy cosmic rays and neutrinos (Falcke & Gorham 2003) allowing for the first time access to particles beyond 1021 eV (Scholten et al. 2006). Apart from the KSPs open access for smaller projects is also planned. Here we give a brief description of the telescope.

We report on results of a program of coordinated multiwavelength observations of single G stars. While the spectral types are restricted to lie within a narrow range of the Sun’s, they have ages ranging from ∼ 70 Myr to ∼ 9 Gyr, which makes them suitable proxies for the Sun at several stages of its life history from the ZAMS to the very late main-sequence phase.

We present the results of photometric and high-resolution spectroscopic studies of a group of B[e] stars (Be stars with warm dust or B[e]Ds) and of two cooler objects with extremely high luminosities (HDE 331319 and IRC+10420). The B[e]Ds is a growing group of objects with very strong emission-line spectra, some of which show direct evidence of the presence of a hot and a cool star in the system. Their basic properties and connection to other groups of binaries are discussed, and a new list of members is presented. Fundamental parameters and chemical composition of an unusual F-supergiant HDE 331319 and recent results on a fast evolving object IRC+10420 are also reported.

Quiescent solar prominences are cool and dense plasma clouds located inside the hot and less dense solar corona. They are highly dynamic structures displaying flows, instabilities, oscillatory motions, etc. The oscillations have been mostly interpreted in terms of magnetohydrodynamic (MHD) waves, which has allowed to perform prominence seismology as a tool to determine prominence physical parameters difficult to measure. Here, several prominence seismology applications to large and small amplitude oscillations are reviewed.

We have tried to find empirical evidence for the role of photospheric motions in the building up of the flare productive magnetic patterns in Active Regions.

The bright Hα faculae are associated with V∥ structures different from a classical Evershed flow and particularly ‘anomalous’ in the regions and periods of high flare occurrence. The flares observed occurred at ‘crossings’ of the lines V∥ = 0(V ≠ 0) and H∥ = 0 and at places where V∥ = 0 showed abrupt changes of direction. It is suggested that these anomalous V∥ structures are evidence of vortex motions.

Although the HST GSC–I (Paper-I: Lasker et al. 1990, Paper-II: Russell et al. 1990, Paper-III: Jenkner et al. 1990) has been used with great success operationally, it was always known that it was possible to improve the scientific and operational usefulness by an increase in scope to include multi-color and multi-epoch data. Once the GSC-II concept was established, it was evident that, even beyond the original motivations in HST operations, it would address a number of other astronomical needs such as increasing demands for fainter catalogues to support remote or queue scheduling capabilities and adaptive optics on the next generation of large-aperture, new-technology telescopes. In addition, the all sky nature of the GSC–II makes it a natural data source for research in galactic structure.

A few of the questions proposed earlier to the contributors are reviewed to identify some of the unsolved problems related to the different interfaces between comets, asteroids, and meteorites and their evolution and origin.

Observations of the large-scale magnetic field show that the current extended solar cycle minimum is different from the three previous well-observed minima. The weaker polar fields increase the relative influence of middle and low-latitude flux patterns on the configuration of the corona and heliosphere. A much larger portion of the open flux originates in equatorial coronal holes. Even though the mean magnetic field of the Sun as a star is the weakest since measurements began, the sector structure of the interplanetary field, though smaller in magnitude, reached fairly high latitude until 2009. The emergence of active regions through the cycle and transport of flux from low to high latitudes also show quite different patterns, providing insight into the dynamo that drives the cycle. Long records of synoptic observations provide a rich source of information about solar activity that must be maintained.

In December, 1973, a Lunar Ejecta and Meteorites (LEAM) experiment was placed in the Taurus-Littrow area of the moon by the Apollo 17 Astronauts. Objectives of the experiment were centered around measurements of impact parameters of cosmic dust on the lunar surface. During preliminary attempts to analyze the data it became evident that the events registered by the sensors could not be attributed to cosmic dust but could only be identified with the lunar surface and the local sun angle. The nature of these data coupled with post-flight studies of instrument characteristics, have led to a conclusion that the LEAM experiment is responding primarily to a flux of highly charged, slowly moving lunar surface fines. Undoubtedly concealed in these data is the normal impact activity from cosmic dust and probably lunar ejecta, as well. This paper is based on the recognition that the bulk of events registered by the LEAM experiment are not signatures of hypervelocity cosmic dust particles, as expected, but are induced signatures of electrostatically charged and transported lunar fines.

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.