The profile of a stellar spectral line is formed by the transfer of radiation through the atmosphere by atomic processes in different chemical elements distributed usually unequally over the surface of a magnetic star.

The theory of model atmospheres accounts for all possible physical conditions. Usually one assumes chemical homogeneity with a plane parallel atmosphere. The resulting line profile, however, is strongly deformed by the geometrical influence of the topographic element distribution and the magnetic surface field structure as well as the projection onto the line of sight of the outgoing radiation from all surface points and its integration over the visible disk.

Line formation by the geometry of projection and element distribution is used for the inverse procedure of Doppler Imaging by V.L. Khokhlova and her followers. We consider here only the influence of the magnetic field on the line profile including the Stokes parameters $I, Q, U, V$, which we study separately from other effects. Thus as a function of the stellar aspect due to rotation the magnetic field and the projection make a symmetric “plane atmosphere profile” asymmetric.

Line profile deformation by the magnetic field leads to a fatal consequence for the traditional measurement of stellar magnetic fields by the Zeeman displacement of the circularly polarized $\sigma$-components. The large scatter of measuring points is partly due to the asymmetry of the line profiles!To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

More than half of all low-redshift AGN exhibit UV and X-ray absorption by highly ionized gas. The observed UV and X-ray absorption lines are almost aiways blue-shifted at velocities of hundreds of km s−1, indicating that the absorbing gas is outflowing from the active nucleus. In some cases the inferred mass flux rivals the Eddington limit of the central black hole, an indication that these outflows are intimately related to the mass accretion and energy generation mechanism in AGN. The ejected material can also have an affect on the interstellar medium of the host galaxy and the surrounding intergalactic medium. Over the past several years, coordinated UV and X-ray observations of several bright AGN at high spectral resolution using HST, FUSE, Chandra, and XMM-Newton have contributed greatly to our understanding of these outflows. I will give an overview of these recent observations, summarize our FUSE survey of low-redshift AGN, and interpret the results in the context of models of winds from accretion disks and thermally driven winds from the obscuring torus.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The data from the Greenwich Observatory for 1879–2003 (cycles 12–23) have been used to plot a time (Carrington rotations) vs. Carrington longitude diagram of distribution of the rotation–summed daily areas for each sunspot group. It has been revealed that most of the sunspots appear as clusters having common sources (Sunspot Formation Zones) that lie on a surface rotating with a period close to the Carrington rotation period $T=27.2753$ days. At the same time both the active longitudes and medium-size spots shift in the Carrington heliolongitude and rotate at an angular velocity corresponding to the rotation period $T\sim26.8-26.9$ days. An attempt is made to explain contradictory data on the character of rotation of sunspots and active longitudes.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

By using the observations of the Extreme-UV Imaging Telescope (EIT), we studied three major solar eruptions from the same super active region NOAA 10486 during the interval of October 26 to November 04, 2003. The three eruptions took place when the active region located on the eastern hemisphere, near the central meridian and on the western limb, respectively. In the first event (Oct 26 event), the coronal disturbance (indicated as an EIT wave) in EUV images was limited east to the central meridian, and there were no solar energetic particles (SEPs) detected. The second event (Oct 28 event) accompanied a nearly entire disk disturbance and very large and prompt SEP enhancements. For the last event (Nov 04 event), there was no obvious coronal disturbance on the disk, and the SEP enhancements were much more gradual. From these observational features, we suggest that different coronal disturbances correspond to different acceleration and propagation histories. A large-scale, cross-disk coronal disturbance may open quite a lot of magnetic field lines in the low corona, facilitating the direct access of flare accelerated SEPs to the Sun-Earth connected interplanetary magnetic field lines. Subsequently the SEP intensity will exhibit a very prompt enhancement.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We discuss evidence in local, present-day clusters of galaxies (from the ENACS survey) about the way in which those clusters have evolved and about the evolutionary relationships between the galaxies of different morphological types in them. This evidence is complementary to that obtained from the study of clusters at intermediate and high redshifts. We argue that the spatial distribution and the kinematics of the various types of galaxies in and outside substructures support the following picture.

The elliptical and S0 galaxies have been around for a long time and have obtained an isotropic velocity distribution. The spatial distribution and kinematics of the early spirals are consistent with the idea that many of their kind have transformed into an S0, but that they have survived, most likely because of their velocities. The distribution and kinematics of the late spirals are consistent with a picture in which they have been accreted fairly recently. They have mildly radial orbits and hardly populate the central regions, most likely because they suffer tidal disruption. Finally, the distribution and kinematics of the galaxies in substructures, when taken at face value, imply tangential velocity anisotropy for these galaxies, but this result may be (partly) due to the procedure by which these galaxies are selected. A first attempt to take the effects of selection into account shows that isotropic (or even mildly radial) orbits of subcluster galaxies cannot be excluded.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The experimental and theoretic investigation of the halo (a detail of local source structure genetically associated with an active region magnetosphere) is presented by the example of the AR 5200 (October, 1988). Accordingly to the high space resolution observations of RATAN-600 and SSRT the emission of this region was almost completely ($\approx 80$%) consist of halo emission. The peculiarities of the observed halo spectrum and polarization with the model explaining these peculiarities are described. It is shown that the inversion phenomenon for the halo is strongly affected by the propagation conditions influence on the polarized emission inside the large source of this emission. The term ‘self-inversion’ is introduced for this effect. Maximum in the halo spectrum at the wavelengths 5–10 cm is clarified by the scattering and by the strong suppression of the emissivity of non-thermal electrons at these and more longer wavelengths.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Using observational data published as phase curves of the effective magnetic field strength $B_{\rm e}(P)$ and the surface field $B_{\rm s}(P)$, magnetic models of three stars with long rotational periods are calculated by the Magnetic Charge Distribution method. For two of these stars (HD 2453 and HD 12288), the structure of the magnetic field can be described well by a central dipole model. The third star (HD 200311) is better fitted by a model of a displaced dipole, being decentered by $\triangle r = 0.08 R$ along the dipole axis.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We use low resolution, near-IR spectra of eight of the most distant quasars known, with redshifts in the range 4.9<z<6.4, to investigate the gas and dust properties in their circumnuclear regions. Half of these quasars are characterized by deep, broad and blueshifted absorption features associated with both high and low ionization species, i.e. they belong to the class of Broad Absorption Line (BAL) quasars, which are associated with powerful outflows of dense gas. The large fraction of BAL quasars, the depth and ionization state of the absorption features suggest that these most distant quasars are surrounded by a much larger amount of dense gas than lower redshift (z<4) quasars. We discuss the possible interpretation of this result in terms of extremely high accretion rates and the association with the early formation of quasars.

The spectral shape of all these very distant quasars, and in particular of the BAL quasars, is bluer than for quasars at z<4, suggesting an evolution of the properties of the dust responsible for the quasar reddening. We show that the observed spectral shape can be explained by an extinction curve due to dust produced by SNe. This finding would address the problem of the dust production at z>6, when the age of the universe was lower than the evolutionary timescales of AGB stars.

Finally, these spectra allow to investigate the Fe/α-element abundance ratio, which is a tracer of the star formation history, through the relative strengths of the FeII UV bump and the MgII doublet. We find indications for a large abundance of Fe even in the most distant quasars at z∼6. This finding requires that a strong burst of star formation occurred in the hosts of these quasars already at z>9.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

For the first time the possible presence of radial gradients of magnetic fields in the atmospheres of three magnetic Ap stars has been critically examined by measurements of the mean magnetic field modulus from spectral lines resolved into magnetically split components lying on the different sides of the Balmer jump. A number of useful diagnostic lines below and above the Balmer discontinuity, only slightly affected by blends, with simple doublet and triplet Zeeman pattern have been identified from the comparison between synthetic spectra computed with the SYNTHMAG code and the high resolution and $S/N$ spectra obtained in unpolarized light with the ESO-VLT UVES spectrograph. For all three stars of our sample, HD 965, HD 116114 and 33 Lib (HD 137949), an increase of the magnetic field strength of the order of a few hundred Gauss has been detected bluewards of the Balmer discontinuity. These results should be taken into account in future modelling of the geometric structure of Ap star magnetic fields and the determination of the chemical abundances in Ap stars with strong magnetic fields.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We studied the association between SEP events during 1977-2003 and related CMEs and found each GLE event was associated with a primary CME, which was faster (average speed $\sim$1762 $km \cdot s^{-1}$) and wider (average angle width of $317^{0}$) than an average CME . All SEP-related CMEs distributed within solar source regions of latitude strip of S$30^{0}$-N$40^{0}$, while 11 (85%)GLE-related CMEs originated from the western hemisphere. These fast halo CMEs (75% full-halo and 25% partial-halo) were associated with type II radio bursts in the decameter hectometer (DH) wavelengths.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The phenomena ($\sim 15$ cases) observed with Siberian Solar Radio Telescope (SSRT) in 2003–2004 years are under investigations. These phenomena are identified with CMEs by LASCO and with the associated active regions (ARs). The structure of low corona above these ARs is studied using the observations with RATAN–600. The aim of this cooperative investigation is to follow this phenomenon at the earliest stage when it is developing in low corona.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We provide the first direct lifting of the mass/anisotropy degeneracy for a cluster of galaxies, by jointly fitting the line of sight velocity dispersion and kurtosis profiles of the Coma cluster, assuming an NFW tracer density profile, a generalized-NFW dark matter profile and a constant anisotropy profile. We find that the orbits in Coma must be quasi-isotropic, and find a mass consistent with previous analyses, but a concentration parameter 50% higher than expected in cosmological $N$-body simulations. We then test the accuracy of our method on realistic non-spherical systems with substructure and streaming motions, by applying it to the ten most massive structures in a cosmological $N$-body simulation. We find that our method yields fairly accurate results on average (within 20%), although with a wide variation (factor 1.7 at 1$\sigma$) for the concentration parameter, with decreased accuracy and efficiency when the projected mean velocity is not constant with radius.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Despite many years of effort, observational studies have not found a strong correlation between the presence of any proposed fueling mechanism and low-luminosity AGN. After a discussion of the mass requirements for fueling, I summarize this observational work and provide a number of hypotheses for why the nature of AGN fueling has remained unresolved. In particular, I stress the potential importance of the increasing number of candidate fueling mechanisms with decreasing mass accretion rate, the relevant spatial scales for different fueling mechanisms, and the lifetime of an individual episode of nuclear accretion. The episodic AGN lifetime is a particularly relevant complication if it is comparable to or shorter than the time that the responsible fueling mechanisms are observationally detectable. I conclude with a number of relatively accessible areas for future investigation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Radio-loud AGNs can inhabit regions with a very rich ISM. The presence of this rich medium is likely related to the origin and evolution of the host galaxy and of the active nucleus. Recent observations show that a large fraction of radio galaxies contains a significant young stellar population. This supports the idea that mergers are responsible for both the starburst phase and the triggering of the nuclear activity. The gas that reaches the central regions can have quite disturbed kinematics, likely due to the effects of the AGN activity and in particular of the powerful radio jets. The recent detection of fast nuclear gas outflows, observed both in ionised and neutral gas, is giving new and important insights into the physical conditions of the gaseous medium around the nucleus and the interaction between the AGN and this medium. Finally, as another example of the interplay between the radio activity and the ISM, the possibility of star formation induced by the passage of the radio jet will be discussed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Height series of Doppler observation in $H_{\alpha}$ and $D_3$ spectral lines of solar spicules obtained by big coronagraph (53 cm) of Abastumani Astrophysical Observatory have been analyzed. Time duration of each height series was 7 s. Totally 8 different heights from the photosphere were covered. Spatial difference between neighboring heights was 1 arc sec. We found the periodic spatial distribution of Doppler velocities during height series in certain spicules. We suggest that the periodic spatial distributions are caused by propagating or standing kink waves. The wave length is found to be in the range 3500–4000 km which probably indicates to the granular origin of the waves.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present new results of our ongoing project to find new magnetic stars in stellar groups and open clusters. Observations are carried out at the 6-m and 1-m telescopes of the Special Astrophysical Observatory. Candidates are selected by analyzing the profiles of the λ5200 broad, continuum features with low resolution spectra (a modification of the Cramer & Maeder method). These candidates are observed then with high resolution and a Zeeman analyzer. We present the measurements of 6 new magnetic stars and discuss results for 2 stars with outstanding magnetic fields. To date we found 31 new magnetic stars, listed for the most part in catalogues of stellar groups. Several stars have very strong magnetic fields, among them is the SrCrEu star HD 178892 with a surface magnetic field ${\rm B}_{\rm s}\geq 20\,{\rm kG}$.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We studied the solar proton differential energy spectra with energy range of 1$\sim$500 MeV at several time intervals during the 2000 July 14 solar flare. The results showed that before flare the spectra could be described by a power law function and after flare the power law spectra still existed above 30 MeV although spectra became softer with time. There was a spectral “knee” occurring at $\sim$30 MeV. We constructed a solar proton differential spectrum from 30 MeV to 3 GeV at peak flux time 10:30 UT and fitted it in the same manner. On the basis of a supposition of having the same power law spectrum in higher energy, we calculated the solar proton integrated fluxes in energy range of from 500 MeV to 20 GeV and compared them with other results obtained from experimental, modeling and theoretical calculations in other big historic SEP events.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the first determination of the pairwise velocity dispersion of galaxies at different luminosity with the final release of the Two-Degree Field Galaxy Redshift Survey (2dFGRS). Our result surprisingly shows that the random velocities of the faint galaxies are very high, around $700 {\rm km\,s}^{-1}$, reaching similar values as the brightest galaxies. At intermediate luminosities slightly brighter than the characteristic luminosity $M_*$, the velocities exhibit a well defined steep minimum near $400 {\rm km\,s}^{-1}$. The result challenges the current halo model of galaxies of Yang et al. that was obtained by matching the clustering and luminosity function of 2dFGRS, and can be an important constraint in general on theories of galaxy formation, e.g., the semi-analytical model. Combining the observed luminosity dependence of clustering, our result implies that quite a fraction of faint galaxies are in massive halos of galaxy clusters as the brightest ones, but most of the $M_*$ galaxies are in galactic halos.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The global bipolar structure of the magnetic surface field is asymmetric for many stars, making its analytical description by an expansion of spherical harmonics problematic because of the coordinates. Landstreet (1970) proposed that the asymmetry could be understood assuming a decentered magnetic dipole in the stellar interior. Its surface field can be calculated for different arrangements inside and outside the star using the Magnetic Charge Distribution method. We demonstrate the effect for the two cases of the shift of the dipole along and perpendicular to the radial direction.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We investigate the line-of-sight velocity oscillations in the sunspot NOAA 0051 during it's disk transit. A favorable concourse of circumstances (observational method, excellent seeing plus intrinsic processes in the sunspot) allowed us to observe in some instances a clear picture of waves propagating in the umbra chromosphere (chevron structure in figure 1). Thus it was possible to measure directly their phase velocity in the immediate region of sunspot umbra. These waves have a period of 2.8 min and propagate from the sunspot center outward with the phase velocity of 45–60 km s$^{-1}$ with the line-of-sight velocity amplitude of about 2 km s$^{-1}$ (figure 2, 3). The waves terminate rather abruptly on the umbra boundary and show no direct linkage with (RPW) running penumbral waves (Zirin and Stein 1972). We pointed out that in our observations the picture of propagation of the waves from the sunspot center in two opposite directions is not accompanied by the propagation of H$\alpha$ umbral flashes in these same directions. Our investigations showed that three-minute oscillations are very poorly pronounced in H$\alpha$ intensity, and no “chevron” structure is present. The spatial coherence of the waves at the umbra center is no more than 2$^{\prime\prime}$. No phase delay was found between line-of-sight velocity signals measured in H$\alpha \pm$0.2 Å and H$\alpha \pm$0.7 Å for a single spatial element. This would imply that the vertical extent of the source is comparable to the observed height scale (1000–1500 km). At the photospheric level there are clearly pronounced periodic motions (T $\sim$5 min) propagating from the umbra and from the superpenumbra to the lines of maximum Evershed velocity. One gets the impression that in some portions the Evershed flow itself is pulsating (Kobanov 2000; Rimmele 1995). Balthasar and Wiehr (1990) developed the idea that the Evershed flows may be a result of superposition of some penumbral structure affected by the underlying oscillating layers. Numerical simulations of wave propagation in a stratified magneto-atmosphere presented by Bogdan et al. (2003) show that the coupling between the fast and slow magneto-acoustic-gravity waves is confined to thin atmospheric layers where the sound speed and the Alfen velocity are comparable in magnitude. Their coherent superposition presents a large variety of Doppler and intensity time series. Interesting, some of their pictures resemble our “chevrons”.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html