In this short letter we present our new work on the coronal emission in a sample of AGN. We used the adaptive optics system NACO on the VLT to obtain high angular resolution images (∼0.15”) of the coronal emission in the vicinity of the central engine.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

SigSpec is a new method to compute the significance of the amplitude levels in the frequency domain, based on the false-alarm probability associated with a peak in the amplitude spectrum. The underlying probability density function (PDF) of the amplitude spectrum generated by pure noise may explicitly be derived if treated as frequency and phase-dependent. A comparison of the analytical solution with the results of extensive numerical calculatgions provides excellent agreement. In addition, the SigSpec software has already demonstrated clear advantages compared with the commonly used Fourier methods in various respects. A few examples for ground-based as well as space photometry are presented.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Formation and evolution of coronal holes of different type are investigated. Occurrence and evolution of coronal holes in active regions are connected to the processes occurring in these active regions in particular with flares and CMEs. Coronal holes which are not connected to active regions reflect distribution of large-scale solar magnetic fields and their dynamics determined by global solar magnetic field structure changes.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present preliminary results of a photometric multisite campaign on the $\delta$ Scuti-type Pre–Main-Sequence star IP Per. Nine telescopes have been involved in the observations, with a total of about 173 hour of observations over around 40 nights. Our current data permitted us to confirm the multiperiodic nature of this star and to determine at least 9 pulsational frequencies. A preliminary nonradial theoretical analysis seems to show that the star pulsates in a mixture of $l=0, 1, 2$ modes.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

According to the current paradigm, galaxies form and reside in extended cold dark matter (CDM) halos and in turn are key tracers of cosmological structure. Understanding how different types of galaxies occupy halos of different masses is one of the major challenges facing extragalactic astrophysics. The observed galaxy properties depend on the environment surrounding the galaxy. Within the framework of most galaxy formation models the environmental dependence of the galaxy population is mainly due to the change of the halo mass function with large-scale environment. Such models make precise predictions for how galaxy clustering should depend on environment. We will illustrate this by presenting analytical models of dark matter and galaxy clustering along with results obtained from numerical simulations. With these results we can hope to obtain a better understanding of the link between galaxies and dark matter and thereby constrain galaxy formation models.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In Eselevich V. and M. Solar Phys. 195, 319, 2000 is shown that in brightness rays of the streamer belt from time to time there exist additional plasma streams of enhanced density moves antisunward and occupies a separate ray. The duration of additional streams can range from a few hours to several days. For that reason, some of them may be categorized as sporadic SW streams and the others as quasi-stationary SW streams. Preliminary investigations showed that the leading edge of such streams can be extremely small in width. The purpose of this paper is to verify the conclusions about the existence of additional plasma streams with steep fronts in streamer belt rays, based on analyzing the calibrated data from LASCO/SOHO C2 and C3.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The emission line spectra of active galactic nuclei fall into three main categories: star formation nuclei (or HII regions), Seyfert nuclei and LINERs (low ionization narrow emission-line regions). A subset of these galactic nuclei has intermediate characteristics between LINERs and HII regions. These so-called transition objects were the subject of numerous studies in the past, but their true nature has remained elusive. It's almost impossible to explain these objects with models that take into account only one ionization mechanism, being it stars, an AGN or shocks. We show how the use of a set of elaborated photoionization models, that account consistently for these parameters (ionization by stars, shocks and/or AGN and dust), constrained by a detailed study of the stellar population properties, can help us understand the nature of these transition objects.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present new spectroscopic observations of the 3.4μm absorption feature in a Seyfert 2 galaxy and a ULIRG. A signature of C–H bonds in aliphatic hydrocarbons, the 3.4μm feature indicates the presence of organic material in Galactic and extragalactic dust. The feature in these galaxies closely resembles that seen in the Galactic diffuse ISM and in newly-formed dust in a protoplanetary nebula. This similarity implies a common composition for the hydrocarbon component of interstellar dust in a range of galaxy types, and one which is resistant to processing in the interstellar and/or circumnuclear medium.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Halo CMEs represent the three-dimensional moving structures, located out of the plane of the sky (Howard et al. 1982, St. Cyr et al. 2000). At that one halo CMEs move toward the Earth (frontside Halo CMEs), other - away from the Earth, St. Cyr. Frontside halo CMEs play the special role in phenomena, associated with space weather, Crosby (2001). The largest geomagnetic storms are caused by influencing such CMEs on the magnetosphere of the Earth (Webb et al. 2000, St. Cyr et al. 2000). Using the images of halo CMEs in the field of view of a coronagraph it is possible to determine only their apparent characteristics in the plane of the sky. But in this case it is difficult define its important parameters such as directions of movement, angular sizes in various sections of CME, position of the CME “center” or of its front, velocities of CME elements along directions which are not located in the plane of the sky. Without these parameters it is impossible to find the mass of CME, it's kinetic and potential energy. In the present work the methods are offered and approved allowing the estimation of the listed above halo CMEs parameters, which are determined with difficulty.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The propagation of cosmological ionization fronts during the reionization of the universe is strongly influenced by small-scale ($\sim$ kpc) gas inhomogeneities caused by structure formation. In this paper we study this important effect by performing detailed radiative-hydrodynamic simulations of photoevaporation of cosmological minihalos (MHs) and incorporating the results into a semi-analytical model of reionization, which also includes the effect of mean intergalactic medium (IGM) clumping and the nonlinear clustering of minihalos. We find that small-scale structures have a significant effect on the process of reionization, slowing it down and extending it in time. This can help in understanding the recent observations by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite, which point to an early and extended reionization epoch.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We report the results of the search for rapid periodic magnetic variations in $\gamma$ Equ. Observations were collected in August 1989 with the 6-m telescope of Special Astrophysical Observatory (Russia). We analysed a 3-hour series of 1720 rapid $B_{\rm e}$ measurements of $\gamma$ Equ obtained with an average time resolution of 6.6 s. A power spectrum analysis shows a period of $P = 3.596\,{\rm min}$. That period differs from the well-known photometric period of rapid variability $P_{\rm phot} = 12.44\,{\rm min}$. We do not confirm variations of the $B_{\rm e}$ field of $\gamma$ Equ with the $P_{\rm phot}$.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Between 2000 and 2003 more than 600 hours of photometric data of the $\delta$ Scuti star 44 Tauri (HD 26322) were collected in Strömgren $v$ and $y$ as well as in Johnson $V$. Observations were carried out at Washington Camp (Arizona), the Sierra Nevada Observatory (Spain) and the Ege University Observatory (Turkey). After analyzing the data with Period98 (Sperl 1998) more than 30 frequencies were found to be significant. We present the data and the results of our observational campaigns.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Coronal holes (CHs) are large-scale regions of the corona with decreased density of material and temperatures. CHs are characterized by predominantly an open configuration of magnetic field lines. CHs are observed as regions of corona with decreased emission in soft X-rays, and appear simultaneously in different emission lines in distinct regions of solar atmosphere, Zirin (1988). CHs are known to be the source of the fast quasi-stationary solar wind (Nolte et al. 1976). At the same time answers to key questions which are related to the originating (the birth) of coronal holes till now are not obtained. It is known a little works in which the birth of CHs were investigated (Solodina et al. 1977; Bohlin & Sheeley 1978; Watari et al. 1995). The objective of this paper is to study the birth of non-polar CHs. This paper continues our paper Fainshtein et al. (2002), in which one the birth of coronal holes was studied.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Mrk 1210 is an Sa galaxy at z = 0.01350. Its optical spectrum displays a strong featureless continuum and Wolf-Rayet features within the central 200 pc (Storchi-Bergmann et al. 1998), evidencing the presence of a circumnuclear starburst. Here, we present SpeX near-infrared (NIR) spectroscopy in the interval 0.8−2.4 μm, combined with optical (3700Å-7400Å) observations, aimed at studying the physical properties of the nuclear and extended gas. Kinematics derived from the line profiles, extinction affecting the emitting gas, temperature and density indicators of the NLR, and excitation sources for the molecular and low-ionization gas are discussed. The presence of high-ionization as well as low-ionization and molecular lines in the optical and NIR spectrum suggests a strong competition between the starburst component and the ionized gas from the central engine. This makes Mrk 1210 an ideal target to study the interplay between starburst and nuclear activity in galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Among variable stars, $\delta$ Scuti are particularly interesting since they can pulsate in different evolutionary phases and are characterized by both radial and nonradial pulsation modes. Even if the majority of $\delta$ Scuti stars are in their Main Sequence (MS) or post-MS phases, there are growing evidences in the recent years about the presence of $\delta$ Scuti variables among stars which are still in their pre-MS phase (the so-called Herbig Ae-stars). Due to the small number of the known class members, the boundaries of Instability Strip are not well constrained. In this context, we present the preliminary results of a long term project to define these limits by enlarging the sample of PMS $\delta$ Scuti stars.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

This paper is devoted to the investigation of the synchronous enhancements of the solar source fluxes according to the RATAN-600 Southern Sector observations at the 1.92 cm, 2.24 cm, 2.74 cm, and 3.21 cm radio waves. The observations were carried out on 11.09.01 from 8:30 UT to 10:30 UT every 8 min. We use the term “synchronous bursts” or “synchronous brightenings” instead of the “sympathetic bursts” as the time resolution of the RATAN - 600 is not high. The solar source brightenings are synchronous if they are registered in 2 - 2.5 min time lag, i.e. in the time interval of passage of the Sun through the central part of the main lobe of the antenna power pattern. The high flux sensitivity of the radio telescope - radiometer system was 0.005 s.f.u. The solar sources were identified with the active regions: AR 9610, AR 9608, AR 9606, AR 9616, AR 9617, which widely separated from each other (up to $10^{6}$ km). According to our observations, the synchronous enhancements were observed at the moments of the soft X ray brightenings and X ray bursts (Figure 1a). The temporal variations of the relative fluxes of the solar sources $F/F_{0}$ were compared to the $X$-ray (GOES 8,10; $H_{\alpha}$ - flares and to the radio bursts at 9100 MHz, $F_{0}$ - the radio emission flux from the “quiet” Sun, $F$ - the radio emission flux from the solar source). It turned out that the interrelationships of the active regions AR 9610, AR 9608, AR 9606 were the most interesting. It was registered 4 synchronous brightenings of solar sources AR 9610, AR 9608 at the moment of the observations: 8:38 UT, 9:02 UT, 9:50 UT, 10:30 UT. We recorded synchronous brightenings of solar sources at 1.92 cm, 2.24 cm, 2.74 cm, and 3.21 cm radio waves: at $\lambda=2.24 cm$ – $\Delta(F)=(0.24 \div 0.88)$ s.f.u. and at $\lambda=3.21$ cm – $\Delta(F)=(0.21 \div 0.94)$ s.f.u. The detailed halo solar source is the magnetosphere, which was identified with all extensive AR 9608 region excepting the primary the most strong solar source of the active region radio emission. The angular size of halo is closed to the angular size of AR 9608 ($7.7 \arcmin$). The comparison of the brightening onset of the AR 9610, AR 9608 interacting active regions in the time interval (9:26 - 9:58 UT) and the discovered forestalling of the halo flux quick intensification at $\lambda=2.24$ cm and $\lambda=3.21$ cm pointed to the active process start in the AR 9608 solar source at $\lambda=3.21$ cm. As it was shown, the dynamics of the time intensity variation of solar sources at $\lambda=3.21$ cm, $\lambda$=2.74 cm is more complicated. It is demonstrated by against of the synchronous of the moments of the AR 9610 relative flux maxima with the $\lambda$ increase (Figure 1b).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Gas in galaxy centers may be irradiated by far-ultraviolet, X-ray photons or both. We discuss the observational line diagnostics for PDRs (FUV) and XDRs (X-ray).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the results of an investigation of the magnetic Ap star HD 965 with high spectral and time resolution. We determine exact radial velocities using spectra obtained with the UVES spectrograph on the ESO VLT. Special attention is given to the spectral lines of the Rare Earth Elements which in roAp stars exhibit the strongest radial velocity variations with pulsation period. Careful time series analysis did not detect any convincing evidence of pulsation in HD 965 with an upper limit in amplitude of $15-20\,{\rm m\,s}^{-1}$.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Popular internal shock models, developed to explain the production of high energy flares in blazar jets, involve collisions between local overdensities of matter being ejected by a central engine and moving along the jet with different velocities. Prior to such collisions, the matter is relatively cold and therefore does not produce intrinsic non-thermal radiation. However, due to Comptonization of external radiation by cold electrons, the presence of such matter should be apparent by prominent precursor soft X-ray flares. We discuss the predicted properties of such precursors.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We report on detection of coronal streamer trace on the night sky over the horizon.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html