Matter Outflows from AGN: A Unifying Model

We discuss a self-consistent unified model of the matter outflows from AGNs based on a theoretical approach and involving data on AGN evolution and structure. The model includes a unified geometry, two-phase gas dynamics, radiation transfer, and absorption spectrum calculations in the UV and X-ray bands. We briefly discuss several questions about the mass sources of the flows, the covering factors, and the stability of the narrow absorption details.Comment: 6 figures, accepted for publication in Astrophysics and Space Scienc

Investigating the reasons of variability in Si IV and C IV broad absorption line troughs of quasars

In this paper we analyze the C IV and Si IV broad absorption troughs of two BALQSOs (J101056.69+355833.3, J114548.38+393746.6) to the individual components they consist of. By analyzing a BAL trough to its components we have the advantage to study the variations of the individual absorbing systems in the line of sight and not just the variations of the whole absorption trough or the variations of selected portions of BAL troughs exhibiting changes. We find that the velocity shifts and FWHMs (Full Width at Half Maximum) of the individual components do not vary between an interval of six years. All variable components show changes in the optical depths at line centers which are manifested as variations in the EW (Equivalent Width) of the components. In both BALQSOs, over corresponding velocities, Si IV has higher incidence of variability than C IV. From our analysis, evidence is in favour of different covering fractions between C IV and Si IV. Finally, although most of our results favour the crossing cloud scenario as the cause of variability, there is also strong piece of evidence indicating changing ionization as the source of variability. Thus, a mixed situation where both physical mechanisms contribute to BAL variability is the most possible scenario

Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. VIII. An intensive HST, IUE, and ground-based study of NGC 5548

We present the data and initial results from a combined HST/IUE/ground-based spectroscopic monitoring campaign on the Seyfert I galaxy NGC 5548 that was undertaken in order to address questions that require both higher temporal resolution and higher signal-to-noise ratios than were obtained in our previous multiwavelength monitoring of this galaxy in 1988-1989. IUE spectra were obtained once every 2 days for a period of 74 days beginning on 1993 March 14. During the last 39 days of this campaign, spectroscopic observations were also made with the HST Faint Object Spectrograph (FOS) on a daily basis. Ground-based observations, consisting of 165 optical spectra and 77 photometric observations (both eco imaging and aperture photometry), are reported for the period 1992 October-1993 September, although many of the data are concentrated around the time of the satellite-based program. These data constitute a fifth year of intensive optical monitoring of this galaxy. In this contribution we describe the acquisition and reduction of ali of the satellite and ground-based data obtained in this program. We describe in detail various photometric problems with the FOS and explain how we identified and corrected for various anomalies. During the HST portion of the monitoring campaign, the 1350 Å continuum flux is found to have varied by nearly a factor of 2. In other wave bands, the continuum shows nearly identical behavior, except that the amplitude of variability is larger at shorter wavelengths, and the continuum light curves appear to show more short­ timescale variability at shorter wavelengths. The broad emission lines also vary in flux, with amplitudes that are slightly smaller than the UV continuum variations and with a small time delay relative to the UV continuum. On the basis of simple time-series analysis of the UV and optical continuum and emission-line light curves, we find (1) that the ultraviolet and optical continuum variations are virtually simultaneous, with any lag between the 1350 Å continuum and the 5100 Å continuum amounting to less than about 1 day; (2) that the variations in the highest ionization lines observed, He II λ1640 and N v λ1240, lag behind the continuum variations by somewhat less than 2 days; and (3) that the velocity field of the C IV-emitting region is not dominated by radial motion. The results on the C IV velocity field are pretiminary and quite uncertain, but there are some weak indications that the emission-line wings (|Δv|≥ 3000 km s-ˡ) respond to continuum variations slightly more rapidly than does the core. The optical observations show that the variations in the broad Hβ line flux follow the continuum variations with time lag of around 2 weeks, about twice the lag for Lyα and C IV, as in our previous monitoring campaign on this same galaxy. However, the lags measured for Lyα, C IV, and Hβ are each slightly smaller than previous determmations. We confirm two trends reported eartier, namely, (1) that the UV /optical continuum becomes "harder" as it gets brighter and (2) that the highest ionization emission lines have the shortest lags, thus indicating radial ionization stratification of a broad-line region that spans over an order of magnitude range in radius