We review the small number of known observations of planetary transits made in Ireland in the 18th century with particular reference to the 1769 observations of Venus by Charles Mason. Though inconclusive, there is evidence to suggest that planetary transits were instrumental in the foundation of at least one of the principal observatories in Ireland. In addition, we note the close personal involvement and the contributions of Nevil Maskelyne, the prime mover of the UK 1769 Transit observations, in the design and equipment of these observatories.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In this review, I will briefly discuss the hypotheses made in the treatment of modern rotating stellar models and review the expected efficiency of mixing along the HR diagram. The role of mixing in the localization of abundance anomalies will also be discussed. Finally, I will show how mass loss and gravitational settling of helium may influence the evolution of rotating stars, and how A stars can play a unique role in constraining our models.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The discovery of “EIT waves” after the launch of SOHO spacecraft sparked wide interest among the coronal mass ejection (CME) community since they may be crucial to the understanding of CMEs. However, the nature of this phenomenon is still being hotly debated between fast-mode wave explanation and non-wave explanation. Accumulating observations have shown various features of the “EIT waves”. For example, they tend to be devoid of magnetic neutral lines and coronal holes; they may stop near the magnetic separatrix between the source region and a nearby active region; they may experience an acceleration from the vicinity of the source active region to the quiet region, and so on. This paper is aimed to review all these features, discuss how these observations may provide constraints for the theoretical models, and point out their implication to the understanding of CMEs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We report the first systematic study of the supercluster-void network in the $\Lambda$CDM concordance cosmology treating voids and superclusters on an equal footing. We study the dark matter density field in real space smoothed with the $L_s = 5$ h−1Mpc Gaussian window. Superclusters and voids are defined as individual members of over-dense and under-dense excursion sets respectively. We determine the morphological properties of the cosmic web at a large number of dark matter density levels by computing Minkowski functionals for every supercluster and void. At the adopted smoothing scale individual superclusters totally occupy no more than about 5% of the total volume and contain no more than 20% of mass if the largest supercluster is excluded. Likewise, individual voids totally occupy no more than 14% of volume and contain no more than 4% of mass if the largest void is excluded. The genus of individual superclusters can be $\sim 5$ while the genus of individual voids reaches $\sim 55$, implying significant amount of substructure in superclusters and especially in voids. Large voids are typically distinctly non-spherical.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We analyse the sensitivity of cosmic shear 2-point statistics to the cosmological parameters, by using Monte Carlo Markov Chain (MCMC) methods. In particular, we investigate degeneracies among parameters and compare them to the CMB ones. Specializing on a Canada France Hawaii Telescope Legacy Survey (CFHTLS) type lensing survey and WMAP-1 year and CBI CMB data, we find cosmic shear information improves CMB cosmological parameters constraints by a factor of 1.5 – 2.5.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We study a simple model for the solar dynamo in the framework of the Parker dynamo, with a nonlinear dynamo saturation mechanism based on magnetic helicity conservation arguments. We find a parameter range in which the model demonstrates a cyclic behaviour with properties similar to that of Parker dynamo with the simplest form of algebraic $\alpha$-quenching. We compare the nonlinear current helicity evolution in this model with data for the current helicity evolution obtained during 10 years of observations at the Huairou Solar Station of China. We conclude that, in spite of the very preliminary state of the observations and the crude nature of the model, the idea of using observational data to constrain our ideas concerning magnetic field generation in the framework of the solar dynamo appears promising.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Young A-type stars in the pre–main-sequence (PMS) evolutionary phase are particularly interesting objects since they cover the mass range ($\sim$1.5-4 $M_\odot$) which is most sensitive to the internal conditions inherited from the protostellar phase. In particular, they undergo a process of thermal relaxation from which they emerge as fully radiative objects contracting towards the Main Sequence. A-type stars also show intense surface activity (including winds, accretion, pulsations) whose origin is still not completely understood, and infrared excesses related to the presence of circumstellar disks and envelopes. Disks display significant evolution in the dust properties, likely signalling the occurrence of protoplanetary growth. Finally, A-type stars are generally found in multiple systems and small aggregates with lower mass companions.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Past X-ray observations by ASCA suggest that warm absorbers (O VII and O VIII edges) are apparently rare in high luminosity AGNs (quasars) while they are more common in low luminosity AGNs (Seyferts). However, this could be a selection effect if high luminosity AGNs have mostly narrow absorption lines (with no strong bound free edges), which escaped detection by the low resolution of ASCA. To check this hypothesis we are studying the high-resolution X-ray spectra of quasars from grating spectrometers on board Chandra and XMM-Newton in search for absorption lines. In this contribution we present spectra of three quasars. The spectra show narrow (several hundred km s−1) absorption and emission X-ray lines from H-like and He-like ions of O, Ne, Mg, and other abundant elements. We also detect absorption from iron L-shell lines and iron M-shell unresolved transition array. We present the analysis of MR2251-178 where we find that at least two, and probably three, distinct warm absorbers are needed to explain the high resolution spectrum of this object. We re-analyze the high-resolution X-ray spectrum of PG 1211+143 and suggest that an outflow velocity of ∼3000 km s−1 provides an adequate explanation to these data. We also present preliminary results form the Chandra/HETGS observation of the quasar 4C74.26.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

When in 1874 and 1882 Venus passed in front of the face of the Sun, most countries with a scientific reputation to keep or to gain made plans to observe the great event. The United States was no exception. The purpose was primarily to measure the solar parallax, and thereby determine the astronomical unit, the distance between the Earth and the Sun. With a $177000 Congressional appropriation for the 1874 event, and $78000 for 1882, the Americans sent out eight well-equipped expeditions for each transit. Under the U.S. Transit of Venus Commission, the responsibility fell to the U. S. Naval Observatory (Dick 2003). Relying heavily on photographic methods, the Americans returned 350 plates in 1874, and 1380 measurable plates in 1882. Simon Newcomb grew skeptical of the results, but in 1894 William Harkness produced a final value of the solar parallax, after adjustments with other constants, of 8.$\rlap^{\prime\prime}$809, with a probable error of 0.\rlap$^{\prime\prime}$0059, yielding an Earth-Sun distance of 92797000 miles, with a probable error of 59700 miles. This was a significant improvement over previous estimates. How important were the transit of Venus observations? In the end it was Newcomb who had the final say, for it was his system of astronomical constants that was adopted internationally at a Paris conference in 1896. Ironically, just at this time other methods were proving more accurate than Venus transits. In determining a final value for the solar parallax from all methods, Newcomb gave all photographic observations of the 1874 and 1882 transit a weight of 2, compared to a weight of 40 for Pulkovo Observatory's determination of solar parallax from the constant of aberration. Thus the Venus transit observations played little role in the official value used for the astronomical unit in the 20th century.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Among more than 120 discovered exo-planets, less than 20 were found in double star systems. Out of this sample we studied the planetary motion in those systems that can be regarded as close binaries, i.e. HD41004 AB, $\gamma$ Cephei and Gliese 86. In this study we concentrate on the first two systems, where the secondaries are M4 V dwarfs at about 20 AU from the host-star. A comparison of previous studies – where the dynamical behavior was studied in the (semi-major axis, inclination) plane (see Dvorak et al. 2003a) for $\gamma$ Cephei and Pilat-Lohinger & Funk (2004) for HD41004 A) – shows significant differences in the stability maps. Our numerical investigation examines the region between 0.5 and 1.2 AU, which is influenced mainly by mean motion resonances when the initial position of the detected planet $a_{gp} < 1.5$ AU. If we move the planet farther away from the host-star (to distances $> 1.5$ AU) we observe an arc-shaped chaotic structure in the dynamical map.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We study the formation and evolution of voids in the dark matter distribution using various simulations of the popular $\Lambda$ Cold Dark Matter Universe. We identify voids by requiring them to be spherical or elliptical regions of space with a mean overdensity of $-0.8$ or less. The distribution of void sizes in the different simulations shows good overlap. The size of a void is related to the depth of the smoothed density field at that position in the initial conditions. The rescaled mass profiles of voids in the different simulations agree remarkably well. We find a universal void mass profile of the form $\rho(\ltr)/\rho(r_{\rm eff}) \propto \exp[(r/r_{\rm eff})^\alpha]$ where $r_{\rm eff}$ is the effective void radius and $\alpha\sim 2$. The mass function of haloes in voids is steeper than that of haloes which populate denser regions.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present a statistical study on the acceleration of CMEs. This study is based on 23 CME events best observed by SOHO LASCO/C1 coronagraph, which observes the inner corona from 1.1 to 3.0 $R_S$. The kinematic evolution of a CME has a distinct acceleration phase that mainly takes place in the inner corona. We find that the acceleration duration distribution ranges from 10 to 1100 min with a median (average) value at 54 min (169 min). The acceleration magnitude distribution ranges from 6 m s$^{-2}$ to 947 m s$^{-2}$ with a median (average) value at 209 m s$^{-2}$ (280 m s$^{-2}$). We also find a good correlation between CME acceleration magnitude A (in unit of m s$^{-2}$) and acceleration duration T (in unit of min), which can be simply described as A=10000/T.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Cyclic variations of the coronal green line brightness (CGLB) are investigated analysing a series of synoptic charts and a special movie assembled of them, covering 1943-2001. Regular changes of the large-scale CGLB distribution in dependence on the phase in the solar cycle are presented. A quantitative relation between the coronal green line intensity $I$ and the total magnetic field strength $B$ is derived for the period 1977-2001; the $B$ was calculated under potential approximation. A simple exponential relation of type $I \propto B^q$ was found to exist between the above two quantities. It is shown that the $q$ exponent may have opposite sign in the equatorial and polar zones. During phases of the solar cycle maxima the $I$ versus $B$ relation is much more complicated and cannot be expressed by such a simple formula.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The voyage of the Mexican commission to observe the transit of Venus on 8 December 1874 in Japan is briefly recounted. The five-man expedition was led by Francisco Díaz Covarrubias. They succeeded in establishing two observing stations near Yokohama, one in Nogue-no-Yama and one on a hill called “The Bluff”, and also in determining precise geographical positions for them. Clear skies allowed the observation of the transit at both stations. The results were presented in Paris in 1875, and published on the same year. They were meant as a contribution to be processed along with all other data obtained by different missions. The importance of the expedition for the development of early modern science in Mexico – particularly astronomy – is examined in the broad context of the social and political conditions then prevailing in the country. The relevance of the mission for the establishment of scientific, cultural and even commercial ties between Japan and Mexico is emphasized.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We discuss follow-up X-ray observations of giant-amplitude, non-recurrent X-ray flares, interpreted as tidal disruptions of stars by supermassive black holes at the centers of the flaring galaxies. The flare observations open up a new window to study supermassive black holes and their environment, and the physics of accretion events, in non-active galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present a model for the distribution of void sizes and its evolution within the context of hierarchical scenarios of gravitational structure formation. For a proper description of the hierarchical buildup of the system of voids in the matter distribution, not only the void-in-void problem should be taken into account, but also that of the void-in-cloud issue. Within the context of the excursion set formulation of an evolving void hierarchy is one involving a two-barrier excursion problem, unlike the one-barrier problem for the dark halo evolution. This leads to voids having a peaked size distribution at any cosmic epoch, centered on a characteristic void size that evolves self-similarly in time, in distinct contrast to the distribution of virialized halo masses in not having a small-scale cut-off.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present predictions for cosmological parameter constraints from combined measurements of second- and third-order aperture mass statistics of cosmic shear. The generalized third-order aperture mass is introduced and its relation to the convergence bispectrum is given. This quantity contains (in principle) all information about the bispectrum. Using ray-tracing simulations, we perform a Fisher matrix analysis for various cosmological parameters and show that the combination of $\langle M_{\rm ap}^2\rangle$ and $\langle M_{\rm ap}^3\rangle$ improves the parameter estimation significantly.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Double-lined-eclipsing binaries are the essential systems for the measurement of stellar masses and radii. About 50-60 systems have components (mostly A-stars) for which these values are known with an uncertainty less than 1-2%. Therefore, these systems are very suitable to improve our understanding of stellar structure and evolution. In this paper, special attention is given to the assessment of the role of internal rotation of the early-type stars in selected double-lined binaries (i.e., EK Cep, PV Cas, and $\theta^2$ Tau): it is shown that adoption of rapidly rotating cores for such stars permits the models to be in very good agreement with the observational results including the apsidal advance rates.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Regularity and chaos of “quasi-stable” (i.e. appearing stable during a finite interval of time) planetary orbits around one component of binary stars is investigated for different values of the binary's mass ratio and orbital eccentricity $e$. The behavior of fictitious planetary orbits around 16 Cyg B-like stars is presented. Among the quasi-stable orbits we found that there exists a (“stability zone”) for every values of $e$, but that the existence of nearly-circular planetary orbits is restricted to values of $e$ less than 0.8. However, not all the quasi-stable orbits are regular: emergence of chaos when $e$ increases is shown in two sets of quasi-stable orbits (each set has fixed initial conditions for the planet, but varying values for $e$ from 0 to 0.99). In the first set, which lies in the “heart” of the stability zone, chaos appears only when $e$ approaches 1. The second one is near the border of the stability zone, and chaos appears as soon as $e$ reaches 0.7. The influence of the binary's orbital eccentricity on the limit between regularity and chaos is therefore stronger in the latter case (wider planetary orbits) than for the former one (closer planetary orbits).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A helical structure in the coronal mass ejection (CME) of 12 September 2000 was observed by the Ultraviolet Coronagraph Spectrometer (UVCS) aboard the Solar and Heliospheric Observatory (SOHO) at heliocentric distances of 3.5 and 6 R$_{\odot}$. A difference of 300 km sec$^{-1}$ in line-of-sight velocities for two segments of the helix obtained from Doppler measurements implies expansion and allows one to distinguish which segment was closest to the observer. The tilt of the segment then determines the handedness. Observed Ly$\alpha$ and C III line emissions indicate that the helix was threaded with filament plasma of varying density. While the helix constituted the bright core of filament plasma, the helix itself was most likely not the pre-existing filament structure.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html