Mass-losing accretion discs around supermassive black holes

We study the effects of outflow/wind on the gravitational stability of accretion discs around supermassive black holes using a set of analytical steady-state solutions. Mass-loss rate by the outflow from the disc is assumed to be a power-law of the radial distance and the amount of the energy and the angular momentum which are carried away by the wind are parameterized phenomenologically. We show that the mass of the first clumps at the self-gravitating radius linearly decreases with the total mass-loss rate of the outflow. Except for the case of small viscosity and high accretion rate, generally, the self-gravitating radius increases as the amount of mass-loss by the outflow increases. Our solutions show that as more angular momentum is lost by the outflow, then reduction to the mass of the first clumps is more significant.Comment: Accepted for publication in Astrophysics & Space Scienc

Probing the extremes of Seyfert activity: BeppoSAX observations of Narrow-Line Seyfert 1 galaxies

Results are presented for the first year of observations of a selected sample of Narrow-Line Seyfert 1 galaxies (Ton S 180, RE J1034+396, Ark 564) obtained with the imaging instruments onboard BeppoSAX. These are the first simultaneous broad band (0.1--10 keV) spectra so far obtained for this class of objects.Comment: Contributed Talk, to appear in : The Active X-ray Sky: Results from BeppoSAX and Rossi-XTE, Nuclear Physics B Proceedings Supplements, L. Scarsi, H. Bradt, P. Giommi and F. Fiore (eds.), Elsevier Science B.V. 6 pages LateX and 8 ps figures, using espcrc2 and epsfi

AGN with extreme X-ray amplitude variations

We present active galactic nuclei (AGNs) that have shown extreme amplitude variability in X-rays. These AGN appear as bright for long periods, but then suddenly become extremely X-ray weak sources. Most likely this behavior is due to strong absorption along the line of sight or by relativistically blurred reflection. Two extreme examples are the Narrow Line Seyfert 1 (NLS1) galaxies WPVS 007 and Mkn 335. WPVS 007 is a peculiar AGN because it combines the properties of a normal NLS1 with those of a broad-absorption line (BAL) quasar, which typically only appear in high-luminousity, high black hole mass systems. Mkn 335 has appeared an an X-ray bright AGN for most of the past few decades, but was caught by Swift in a deep X-ray flux minimum state in 2007, and has remained in that state for most of the time since. One potential explanation for this low state is absorption. Several Other AGN have been in deep minimum X-ray flux states, including PG 0844+349 and 1H 0707–495, for which the dramatic drops in X-ray flux have been explained by blurred X-ray reflection

AGN with extreme X-ray amplitude variations

We present active galactic nuclei (AGNs) that have shown extreme amplitude variability in X-rays. These AGN appear as bright for long periods, but then suddenly become extremely X-ray weak sources. Most likely this behavior is due to strong absorption along the line of sight or by relativistically blurred reflection. Two extreme examples are the Narrow Line Seyfert 1 (NLS1) galaxies WPVS 007 and Mkn 335. WPVS 007 is a peculiar AGN because it combines the properties of a normal NLS1 with those of a broad-absorption line (BAL) quasar, which typically only appear in high-luminousity, high black hole mass systems. Mkn 335 has appeared an an X-ray bright AGN for most of the past few decades, but was caught by Swift in a deep X-ray flux minimum state in 2007, and has remained in that state for most of the time since. One potential explanation for this low state is absorption. Several Other AGN have been in deep minimum X-ray flux states, including PG 0844+349 and 1H 0707–495, for which the dramatic drops in X-ray flux have been explained by blurred X-ray reflection

RX J1624.9+7554: A new X-ray transient AGN

SIGLEAvailable from: www.mpa-garching.mpg.de / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Steps toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XII. Ground-based Monitoring of 3C 390.3

Results of a ground-based optical monitoring campaign on 3C 390.3 in 1994-1995 are presented. The broadband fluxes (B, V , R, and I), the spectrophotometric optical continuum flux Fλ(5177 Å), integrated emission-line fluxes of Hα, Hβ, Hγ, He I λ5876, and He II λ4686 all show a nearly monotonic increase with episodes of milder short-term variations superposed. The amplitude of the continuum variations increases with decreasing wavelength (4400-9000 Å). The optical continuum variations follow the variations in the ultraviolet and X-ray with time delays, measured from the centroids of the crosscorrelation functions, typically around 5 days, but with uncertainties also typically around 5 days; zero time delay between the high-energy and low-energy continuum variations cannot be ruled out. The strong optical emission lines Hα, Hβ, Hγ, He I λ5876 respond to the high-energy continuum variations with time delays typically about 20 days, with uncertainties of about 8 days. There is some evidence that He II λ4686 responds somewhat more rapidly, with a time delay of around 10 days, but again, the uncertainties are quite large (~8 days). The mean and rms spectra of the Hα and Hβ line profiles provide indications for the existence of at least three distinct components located at ±4000 and 0 km s-1 relative to the line peak. The emission-line proÐle variations are largest near line center