Lenses acting on the Cosmic Microwave Background can potentially be a very efficient and robust probe of the large-scale matter distribution in the Universe. Their most immediate signature is the way they affect the statistical properties of both the temperature and the polarization fields, in particular they both induce non-Gaussian properties that can be explicitly computed.

Investigations of those effects led to the elaboration of specific reconstruction procedures that aim at mapping the projected mass responsible of the lens effects. These techniques are now on solid ground and are remarkably efficient. However it is likely that our best chance to detect a lensing signal in CMB data in the coming years will be through the cross-correlation patterns they induce between CMB data and tracers of the large-scale structure. Clearly the detection of such an effect would be very fruitful in scrutinizing the gravitational instability picture.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

With the advent of the 2004 transit of Venus, interest in historical observations of past transits has been rekindled. We present evidence suggesting that the Maya of the post-classic period actually observed at least one transit of Venus. The frescoes of Mayapan, which are proposed as a record of 12$^{{\rm th}$- or 13$^{{\rm th}}$-century transits, are described and discussed in their astronomical contextTo search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The photographic observations of 51 Peg with the known planetary companion which has been discovered on the basis of radial velocities (Mayor and Quelos 1995), are being performed at Pulkovo since 1995 by means of 65 cm refractor. So far 46 plates with 170 individual positions have been obtained. The mean error of one exposure is $0.^{\prime\prime}031$ and the error of one plate is $0.^{\prime\prime}020$. The external error of one plate or the error of unit weight is $0.^{\prime\prime}033$, while the error of one yearly position equals to $0.^{\prime\prime}010$. The aim of our observations is to investigate whether this star has some satellites of low mass (stellar or substellar) with periods of rotation from some years to a decade, or more. At present we have the possibility to study its motion over a time span of 8 years and to learn of probable perturbations due to the presence of possible satellites with the periods 0.5–6.0 years and with masses more than $0.2M_\odot$. The absence of satellites with such periods and masses has been shown by means of our observations. The results are compared with the Pulkovo series of the star Gliese 623, whose satellite with the period of $3.76$ yr and mass of $0.09M_\odot$, has been confirmed by observations.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We quantify the importance of mass accretion during AGN phases in the growth of supermassive black holes (BH) by comparing the mass function of black holes in the local universe with that expected from AGN relics, which are black holes grown entirely with mass accretion during AGN phases. The local BH mass function (BHMF) is estimated by applying the well-known correlations between BH mass, bulge luminosity and stellar velocity dispersion to galaxy luminosity and velocity functions. The density of BHs in the local universe is $\rhoBH = 4.6_{-1.4}^{+1.9}\, h_{0.7}^2 \rhoBHunits$. The relic BHMF is derived from the continuity equation with the only assumption that AGN activity is due to accretion onto massive BHs and that merging is not important. We find that the relic BHMF at z = 0 is generated mainly at z<3. Moreover, the BH growth is anti-hierarchical in the sense that smaller BHs ($M_{BH}<10^{7}M_\odot$) grow at lower redshifts (z<1) with respect to more massive ones (z∼1−3). Unlike previous work, we find that the BHMF of AGN relics is perfectly consistent with the local BHMF indicating the local BHs were mainly grown during AGN activity. This agreement is obtained while satisfying, at the same time, the constraints imposed from the X-ray background. The comparison with the local BHMF also suggests that the merging process is not important in shaping the relic BHMF, at least at low redshifts (z<3). Our analysis thus suggests the following scenario: local black holes grew during AGN phases in which accreting matter was converted into radiation with efficiencies ε = 0.04−0.16 and emitted at a fraction λ = 0.1−1.7 and emitted at a fraction λ = 0.1−1.7 of the Eddington luminosity. The average total lifetime of these active phases ranges from $\simeq 4.5\times 10^{8}$ yr for $M_{BH}<10^{8}M_\odot$ to $\simeq 1.5\xten{8}$ yr for $M_{BH}>10^{9}M_\odot$.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Putting their chemically peculiarities aside, Ap and Am stars have many common properties. The discriminating property between them could be the rotation of their interiors beneath their slowly rotating surface. In the PV Cas (HD 240208) binary system whose light curve shows Ap-like variation, the agreement between the theoretical and observed apsidal advance rate is satisfied only with differentially rotating models of the component stars in which rapid rotation is extended almost to the surface. Thus, it seems that there is a steep rotation rate gradient near the surface of the Ap stars. The conclusion we reach in the analysis of PV Cas system leads us to introduce the effective mass as a new conceptual tool in stellar astrophysics: $M_{\rm eff}= M_\star (1-\bar{\Lambda})^{1.75}$, where $M_\star$ and $\bar{\Lambda}$ are mass of the star and average of ratio of centrifugal to the gravitational acceleration throughout the model, respectively. We find that the effective mass of PV Cas A whose true mass is $2.82\pm 0.05\,M_\odot$ is $2.6\,M_\odot$ for both solar and metal rich compositions.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The cross-correlating cosmic microwave background (CMB) fluctuations caused by the Sunyaev-Zel'dovich effect from observed clusters of galaxies with their redshifts can be used to measure the mean squared cluster peculiar velocity with an error $\sigma_{C_S^2}\simeq (300{\rm km/s})^2$. This can be done around $z\gt0.3$ with clusters of flux above 200 mJy which will be detected by PLANCK, coupled with high resolution microwave images to eliminate the cosmological part of the CMB fluctuations. The latter can be achieved with observations by the planned ALMA array or the NSF South Pole telescope and other surveys. By measuring the rms peculiar velocity of clusters and their bulk flow in, e.g., 4 spheres of $\sim 100h^{-1}$ Mpc at $z=0.3$, we could have a direct measurement of the matter density $0.21\lt\Omega_m\lt0.47$ at 95% confidence level.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Due to the optically thin nature of the white light emission, all measurements of the energetics and dynamics of a CME are based on sky-plane projected quantities. The extent and distribution of the CME material along the line of sight is unknown. Thus, CME measurements have an inherent degree of uncertainty. In this paper, I identify the various (possible) sources of errors associated with measurements of CME mass and energy (e.g., instrumental, random, projections effects, etc) and give an error budget for the final measurements. I apply these errors to the statistics of mass and energy for several thousand CMEs observed with LASCO in 1996-2003.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present a statistical investigation of soft X-ray (SXR) solar flare occurrence over the last three 11-yr solar cycles (SCs 21-23, corresponding to the period 1976-2003). We studied not only the monthly number of flares, but we also used an index that estimate the energy emitted by flares in the SXR 1-8 Å band ($Q_{x}$) that we find it better defines their importance in the solar activity cycle. The medium and high importance SXR flares (M&X class) seem to reflect the cycle importance given by the smoothed monthly Wolf numbers (W). SXR flare indices show a delay regarding the sunspot numbers for SC 21, while for SC 22 and 23 their time distribution is almost coincident with W. The level of energy emitted by SXR flares, quantified through the $Q_{x}$ index, is about the same for SCs 21-23 despite the difference between the W curves in the cycles. We also point out the SXR flare behaviour on the cycles descendant phases, with short but intense increases in their activity, that might give useful information about the activity level of the next cycle.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Several recent papers have studied lensing of the CMB by large-scale structures, which probes the projected matter distribution from $z=10^3$ to $z\simeq 0$. This interest is motivated in part by upcoming high resolution, high sensitivity CMB experiments, such as APEX/SZ, ACT, SPT or Planck, which should be sensitive to lensing. In this paper we examine the reconstruction of the large-scale dark matter distribution from lensed CMB temperature anisotropies. We go beyond previous work in using numerical simulations to include higher order, non-Gaussian effects and find that the convergence and its power spectrum are biased, with the bias increasing with the angular resolution. We also study the contamination by the kinetic Sunyaev-Zel'dovich signal, which is spectrally indistinguishable from lensed CMB anisotropies, and find that it leads to an overestimate of the convergence. We finish by estimating the sensitivity of the previously cited experiments and find that all of them could detect the lensing effect, but would be biased at around the 10% level.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present new observations in X-ray and optical/ultraviolet of the nucleus of NGC 1097 known for the abrupt appearance of broad, double-peaked Balmer lines in its spectrum in 1991. These new observations are used to construct the spectral energy distribution (SED) of the central engine. From the SED we infer that this AGN is radio-loud and has a bolometric luminosity $L_{\rm Bol} \sim 10^{42} \: \textrm{erg s}^{-1}$, implying a low Eddington ratio of $L_{\rm Bol}/L_{\rm Edd} \sim 10^{-4}$. These results suggest that the central ionizing source is an advection-dominated accretion flow (ADAF) in the form of an ellevated structure which photoionizes an outer thin disk. We fit a simplified ADAF model to the SED and obtain limits on the values of the mass accretion rate $\dot{M}$ and accretion efficiency η, namely $\dot{M}/{\dot{M}_{\rm Edd}} \gtrsim 10^{-3}$ and $\eta \lesssim 10^{-2}$. We identify an ‘energy budget’ problem: if the central photoionizing source is isotropic, the covering factor of the line-emitting portion of the thin accretion disk is ≈6, i. e. the central source accounts for only 20% of the energy emitted in the double-peaked Balmer lines.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

An account is given of Lord Lindsay's lavishly equipped independent expedition to the Island of Mauritius in the Indian Ocean to observe the 1874 Transit of Venus. The expedition's secondary programme, the deriving of the solar parallax from observations of the minor planet Juno, is also described. This work proved a positive outcome of a generally disappointing event and brought about an important shift in the approach to the parallax challenge. The site on Mauritius where Lord Lindsay observed the Transit in 1874, now preserved as a National Monument, was the centre of celebrations during the Transit of 2004.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Central regions of superclusters are the ideal places where to study cluster merging phenomena: in fact the accretion activity is enhanced, as predicted by the cosmological simulations. In this paper I review the case-study of the Shapley Concentration, aimed to understand the effect of major mergings on the intracluster medium and the galaxy population of the involved clusters.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In this work we focus on UVCS data acquired during the November 2002 SOHO–Ulysses quadrature, at an altitude of 1.7 R$_{\odot}$ over a range of latitudes centered around 27$^{\circ}$N in the western quadrant. A couple of hours before our observations started, a CME event (November 26, 15:30 UT) originating at about 27$^\circ$N, disrupted the coronal configuration of the region. In the $\sim$ 2.3 days following the event UVCS detected emission in the neutral H $Ly \beta$ and $Ly \gamma$ lines as well as in lines from both high and low ionization ions such as C iii, O vi, Si viii, ix and xii, Fe x and xviii. Enhanced emission from the hot Fe xviii ion ($\log T_{max} = 6.7$), lasting nearly to the end of our observations and originating in a region between 10$^\circ$N and 30$^\circ$N, has been identified with a post–CME current sheet. Our interpretation is supported by EIT Fe xii images which show a system of loops at increasingly higher altitudes after the event. Northward of the CME, UVCS observed repeated, sudden and short lived emission peaks in the “cool” $Ly \beta$, $Ly \gamma$, C iii and O vi lines. These events seem to be the extension at higher altitudes of the chromospheric plasma jets observed in the EIT He ii images. Electron temperatures of both the hot and cool region will be presented here and their time evolution will also be illustrated.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We reanalyzed high quality spectra of 158 stars of spectral types A0–F1 and $v\,\sin{i}$ values between 60 and 150 km s$^{-1}$. Using a least squares deconvolution technique we extracted high $S/N$ broadening profiles and determined the loci of the Fourier transform zeros $q_{1}$ and $q_{2}$ where the $S/N$-ratio was high enough. For 78 stars $q_{2}$ could be determined and the ratio $q_{2}/q_{1}$ was used as a shape parameter sensitive to solar-like differential rotation (the equatorial velocity is faster than the near polar velocities). Seventy-four of the 78 stars have values of $q_{2}/q_{1}$ consistent with solid body rotation; in four of the 78 cases, values of $q_{2}/q_{1}$ are not consistent with rigid rotation. Although these stars may be binaries, none of their profiles shows any signatures of a companion. The Fourier transforms do not indicate any distortions and the broadening profiles can be considered due to single objects. One of these candidates may be an extremely rapid rotator seen pole-on, but for the other three stars of spectral types as early as A6, differential rotation seems to be the most plausible explanation for the peculiar profiles.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The variability of solar radiance over a solar cycle is thought to be a delicate balance between the radiative deficit of sunspots and the extra contribution of plage and network regions. Although the net effect is tiny, it must imply structural and thermal changes in the Sun or in partial layers of it as an unavoidable consequence of the virial theorem. Using the virial theorem for continua including the magnetic field it is shown, how solar radiance variability might be connected to a deeply seated flux-tube dynamo and how this connection is established on a hydrodynamical time-scale.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Results of the photographic observations of 61 Cyg are given. The orbital elements and mass ratio of the components of the pair are calculated. The preliminary orbit of a hypothetical satellite with a period of 6.5 yr is given.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the results of a search for gravitational lensing of the cosmic microwave background (CMB) in cross-correlation with the projected density of luminous red galaxies (LRGs). The CMB lensing reconstruction is performed using the first year of Wilkinson Microwave Anisotropy Probe (WMAP) data, and the galaxy maps are obtained using the Sloan Digital Sky Survey (SDSS) imaging data. We find no detection of lensing; our constraint on the galaxy bias derived from the galaxy-convergence cross-spectrum is $b_g=1.81\pm 1.92$ ($1\sigma$, statistical), as compared to the expected result of $b_g\sim 1.7$ for this sample. We discuss possible instrument-related systematic errors and show that the Galactic foregrounds are not important. We do not find any evidence for point source or thermal Sunyaev-Zel'dovich effect contamination.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The rotational evolution of the radiative zone of magnetic Ap stars is investigated with numerical simulations. An angular-velocity profile decreasing with axis distance in combination with a magnetic field leads to a magnetorotational instability. The resulting flows efficiently transport angular momentum outwards. The corresponding decay of angular-velocity gradients in the radiative zone is estimated to take about 10–100 million years.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The early gas and dust protosolar nebula of the solar composition is considered analytically. A simultaneous formation of the sun and all the planets around it ($\approx 5 \times 10^9$ yr ago) through a local gravitational Jeans-type instability of small-amplitude gravity perturbations in the nebula disk is suggested. It is shown that a collective process, forming the basis of the disk instability hypothesis, solves with surprising simplicity the two main problems of the dynamical characteristics of the system, which are associated with its observed spacing and orbital momentum distribution, namely, Bode's law on planet spacing and the concentration of angular momentum in the planets and mass in the sun. Besides, the analysis is found to imply the existence of new planets or other Kuiper-type belts of comets at mean distances from the sun of 87 AU, 151 AU, 261 AU, 452 AU, 781 AU (Mercury, Venus, $\ldots$, Asteroid belt, $\ldots$, Neptune, Kuiper belt, new planets or other Kuiper-type belts).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Ground based radio imaging observations play an useful role in the study of mass ejections from the solar corona since they do not have the limitation of an occulter and both the disk/limb events can be detected early in their development, particularly via the thermal bremmstrahlung emission from the frontal loop of the CME. I present here some of the recent results on the above topic using data obtained with the Gauribidanur radioheliograph, near Bangalore in India.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html