We have modeled the time-variable profiles of the Hα emission line from the non-axisymmetric disk and debris tail created in the tidal disruption of a solar-type star by a $10^{6} M_{\odot}$ black hole. We find that the line profiles at these very early stages of the evolution of the post-disruption debris do not resemble the double peaked profiles expected from a rotating disk since the debris has not yet settled into such a stable structure. The predicted line profiles vary on fairly short time scales (of order hours to days). As a result of the uneven distribution of the debris and the existence of a ‘tidal tail’ (the stream of returning debris), the line profiles depend sensitively on the orientation of the tail relative to the line of sight. Given the illuminating UV/X-ray light curve, we also model the Hα light curve from the debris.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Several radio-loud objects exhibit a complex structure when observed at radio wavelengths: a stationary core, which is thought to harbour the central engine that powers the AGN phenomena, and a relativistic jet, formed by several superluminal components. In some cases, jet components are ejected with different apparent proper motions and directions on the plane of the sky. Moreover, these sources can also show signatures of long-term periodic variability in their historical optical light curve. In this work, we selected the objects 3C 120 and 3C 345, which exhibit both characteristics mentioned above, and interpret them in the framework of jet inlet precession. A brief discussion about what kind of mechanism could be responsible for jet precession is also presented.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present long-slit HST/STIS measurements of the ionized-gas kinematics in the nucleus of three disk galaxies, namely NGC 2179, NGC 4343, NGC 4435. The sample galaxies have been selected on the basis of their ground-based spectroscopy, for displaying a strong central velocity gradient for the ionized gas, which is consistent with the presence of a circum nuclear keplerian disk (CNKD, Bertola et al. 1998; Funes et al. 2002) rotating around a super massive black hole (SMBH). For each target galaxy we obtained the Hα and [NII] 6583 Å kinematics along the major axis and two 0."25 parallel offset positions. Out of three objects only NGC 4435 turned out to have a disk of ionized gas in regular motion and a regular dust-lane morphology. Preliminary modeling indicates a SMBH mass (M[bull ]) one order of magnitude lower than the one expected from the M[bull ]−σc relation for galaxies (Ferrarese & Merritt 2000; Gebhardt et al. 2000).To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We study the NLR emission line spectrum of 12 NLS1s to constrain the EUV – soft X-ray continuum SED using accurate photoionization modeling. We find that the NLR emission line ratios, which we measure for several NLS1 galaxies, can be reproduced within ±15% without a strong BBB component in the framework of a two-component model.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Brightness variations across the entire electromagnetic spectrum, occurring at several time scales, are known properties of blazars. The variability of the continuum emission may be related to the formation and propagation of shock waves in the relativistic jet. In this case we may expect variations also in the degree of polarization and its position angle. In order to effectively constrain such models, we begun in 2003 a program to monitor the optical polarimetry of a sample of blazars, of which we present here the first results.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

High resolution radio and X-ray observations of a subsample of composite LINER/H II galaxies with arcsec-scale radio cores were obtained. These observations yield a 12% detection rate of low luminosity AGN among the entire composite sample in the Palomar survey. Four of these low luminosity AGN also possess sub-parsec jet-like radio extensions. While canonical advection-dominated accretion flows may be responsible for the radio and X-ray emission in submillijansky cores like NGC 7331, they do not appear consistent with the radio emission in these milliarcsecond-scale radio cores; the latter sources are more likely to have an energetically important contribution from a radio-emitting jet.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Spectroscopic optical data (∼4200-6300 Å in the rest-frame) acquired during the monitoring of some QSOs seem to confirm that AGN spectra normally harden at higher luminosities. Focusing only on the global trend (i.e. comparing different objects), the implications in deriving luminosities using optical photometric data (through the K-correction) is briefly outlined here, as well as the result of its parameterization for calculating BH masses through the M$_{BH} \propto$ L$_V^\gamma$ (FWHM Hβ)2 virial relation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present the results of over 20 years of optical spectroscopic monitoring of the prototypical double-peaked emitter, Arp 102B. Its distinct double-peaked, extremely broad (FWHM ≈15,000 km s−1) low-ionization lines (Hα, Hβ, and Mg II) are well-modeled by emission from photoionized gas in a relativistic Keplerian accretion disk around a central black hole (Chen & Halpern 1989; Halpern et al. 1996). A ubiquitous property of double-peaked emitters is long-term variability in the shape of their line profiles on the timescale of months to years, which is consistent with the dynamical timescale of an accretion disk. This variability can be attributed to inhomogeneities in the line-emitting disk, i.e., hot spots, spiral arms, eccentricity, and warps. We characterize the profile variability of Arp 102B in detail, and use it to constrain physical models for the structure and dynamics of its line-emitting accretion disk.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present a new sample of 30 nearby (z < 0.2) BL Lacs, selected to study the nuclear as well as the large scale properties of low power radio sources. New VLA and VLBA radio data have been obtained to discuss the morphology, physical properties, and overall properties of the sample. We show that the distributions of total radio power and intrinsic core radio power for BL Lacs are consistent with their being drawn from the same population as FR I radio galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

This paper describes some useful results that can be obtained through long-term infrared photometric monitoring of Seyfert galaxies.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A systematic study of 30 Radio Loud AGNs available in the BeppoSAX archive has been carried out. The sample consists of 9 Broad Line radio Galaxies, 5 Steep Spectrum Radio Quasars and 16 Flat Spectrum Radio Quasars. These objects represent, according to Unified Models, objects with decreasing viewing angles. Our analysis shows considerable differences between FSRQs and BLRGs'SSRQS. As expected in the AGN Unified Model: i) the X-Ray spectrum of FSRQs is a simple power law with a hard spectral slope (the only exception being 3C273), ii) Broad Line and Steep Radio Spectrum AGNs show a steeper X-Ray continuum and Seyfert like features. We also find that the Fe line is weaker than in radio quiet objects. However no strong evidence emerges that a jet contamination may be the main responsible for the EW shrinking in BLRGs and SSRQs. Recent XMM-Newton observations of Pictor A, 3C445 and PKS 2152-69 confirm the nuclear BeppoSAX results and better constrain the Fe line parameters.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We analyzed 13 narrow-line Seyfert 1 galaxies (NLS1s) observed with XMM-Newton. Their X-ray continua are well parameterized by a combination of a hard power law and thermal emission from a standard Shakura-Sunyaev accretion disk. However, the observed disk temperatures are significantly higher than the prediction from the standard disk, and the temperatures are distributed within an extremely narrow range (0.15–0.22 keV) in spite of the wide range of luminosities (LX = 1041–45 erg s−1). Furthermore, we found an anti-correlation between the disk temperature and luminosity of PKS 0558–504. These results strongly indicate the breakdown of the standard accretion picture in NLS1s. We suggest that a slim disk, which is a stable disk solution under a high mass-accretion rate, could be able to explain the observational results, if the photon trapping effect is properly taken into account.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We determined a central black hole mass of $M_{\rm virial}=1.8\pm 0.4\times 10^{7} M_{\odot}$ in the Seyfert galaxy Mrk 110 with reverberation mapping methods – i.e. from integrated optical line profile variations as well as from velocity-delay maps. But this black hole mass depends on the unknown orientation of the central accretion disk. Here we report on the detection of gravitational redshifted emission in the variable fraction of all broad optical emission lines in Mrk 110. We derive a central black hole mass of $M_{\rm grav}=14.0\pm 3.0\times 10^{7} M_{\odot}$ with this method. This value is independent on the orientation of the accretion disk. A comparison of both black hole mass estimates allows to determine the central accretion disk inclination angle i to 21° in Mrk 110, and therefore the orientation of the spin axis of the central black hole.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

An increasing number of AGNs exhibit broad, double-peaked Balmer emission lines, which arise from the outer regions of the accretion disk which fuels the AGN. The line profiles vary on timescales of 5–10 years. Our group has monitored a set of 20 double-peaked emitters for the past 8 years (longer for some objects). Here we describe a project to characterize the variability patterns of the double-peaked Hα line profiles and compare with those of two simple models: a circular disk with a spiral arm and an elliptical disk.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

By fitting to the quiescent galaxy MBH−σ∗ relation, we calculate the average shift required to scale reverberation-mapped AGN masses to the same zero-point. We use reanalyzed virial products (rV2/G) and both new and published velocity dispersions to find the offset in the AGN calibration. This scaling factor, 〈f〉, accounts for the detailed dynamics and geometry of the broad-line region (BLR). Finally, we confirm the rough correlation between σ∗ and FWHM([O III]) for these 16 AGNs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We collected X-ray and optical images for a X-ray flux-limited, complete sample of 93 active galactic nuclei (AGNs) at z<0.1, selected from the ROSAT Bright Survey. By modeling the host galaxy and the central AGN, we decompose the optical emission into nuclear, bulge and disk components. We cross-correlated our sample with the NVSS and FIRST radio catalogs, and, due to their limited sky coverage, 53 matches were found. We find that the nuclear optical luminosity, thought to be associated with the accretion disk surrounding the active black hole, correlates with the X-ray luminosity, the radio luminosity, and the black hole mass.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We announce the construction of an Atlas of STIS-HST Spectra of Seyfert Galaxies, covering the UV and/or optical spectral range. Nuclear spectra of these galaxies have been extracted in windows of width 0.2″ for an optimized sampling (as this is the width of the slit in most cases), from a long-slit spectrum usually covering 52″. Extranuclear spectra have also been extracted, usually using larger windows to improve signal-to-noise ratio. Spectra obtained with different gratings have been combined in order to provide the largest possible wavelength coverage for each galaxy.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Can we determine spin parameters of black holes by observations of black hole shadows in accretion disks? In order to answer this question, we have investigated shapes and positions of black hole shadows in optically thick accretion disks around Kerr black holes. In conclusion, in order to measure black hole spin parameters from shapes and positions of black hole shadows, it is crucially important to determine a position of a mass centers of a black hole in a region of a black hole shadow.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Integral Field Spectroscopy provides a powerful new tool for disentangling the complex structure of Active Galactic Nuclei—allowing 2D mapping of the distribution, kinematics and excitation of ionized gas and of stellar velocity profiles and populations. Such comprehensive datasets are likely to reveal important clues about the physics of the narrow line region, interactions with the host galaxy and central dynamical forces. Here we present observations of the central regions of NGC1068, obtained using the visible-wavelength GMOS-IFU at Gemini North and NGC4151, taken with a prototype near-infrared fibre IFU at the UK Infrared Telescope.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

I describe very briefly the new libraries of empirical spectra of stars covering wide ranges of values of the atmospheric parameters Teff, log g, [Fe/H], as well as spectral type, that have become available in the recent past, among them the HNGSL, MILES, UVES-POP, and Indo-US libraries. I show the results of using the HNGSL to build population synthesis models. These libraries are complementary in spectral resolution and wavelength coverage, and will prove extremely useful to describe spectral features expected in galaxy spectra from the NUV to the NIR.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html