Chris Done

ABSTRACT Ultra-fast outflows (UFOs) are seen in many AGN, giving a possible mode for AGN feedback onto the host galaxy. However, the mechanism(s) for the launch and acceleration of these outflows are currently unknown, with UV line driving apparently strongly disfavoured as the material along the line of sight is so highly ionised that it has no UV transitions. We revisit this issue using the Suzaku X-ray data from PDS 456, an AGN with the most powerful UFO seen in the local Universe. We explore conditions in the wind by developing a new 3-D Monte-Carlo code for radiation transport. The code only handles highly ionised ions, but the data show the ionisation state of the wind is high enough that this is appropriate, and this restriction makes it fast enough to explore parameter space. We reproduce the results of earlier work, confirming that the mass loss rate in the wind is around 30% of the inferred inflow rate through the outer disc. We show for the first time that UV line driving is likely to be a major contribution to the wind acceleration. The mass loss rate in the wind matches that predicted from a purely line driven system, and this UV absorption can take place out of the line of sight. Continuum driving should also play a role as the source is close to Eddington. This predicts that the most extreme outflows will be produced from the highest mass accretion rate flows onto high mass black holes, as observed.

We compute the Fourier phase spectra for the light curves of five low-luminosity active galactic nuclei observed by EXOSAT. There is no statistically significant phase coherence in any of them. This statement is equivalent, subject to a technical caveat, to a demonstration that their fluctuation statistics are Gaussian. Models in which the X-ray output is controlled wholly by a unitary

... However, a nonthermal electron distribution (as suggested by the rapid X-ray variability, Liang & Nolan ... If X-rays illuminate an optically thick accretion flow, as expected if it forms an ... Makishima 1986) and changing the line equivalent width (Ross & Fabian 1993; Matt, Fabian, & ...

AN IONIZED ACCRETION DISK IN CYGNUS X-1 C. DoNE,"2 JS MULCHAEY,3'4 RF MUSHOTZKY, AND KA ARNAUD3 Laboratory for High Energy Astrophysics, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 Received 1991 September 30; accepted 1992 ...

We show that the low-frequency quasi-periodic oscillations (QPOs) seen in the power-density spectra of black hole binaries (and neutron stars) can be explained by the Lense-Thirring precession. This has been proposed many times in the past, and simple, single-radius models can qualitatively match the observed increase in QPO frequency by decreasing a characteristic radius, as predicted by the truncated disc models. However, this also predicts that the frequency is strongly dependent on spin, and gives a maximum frequency at the last stable orbit which is generally much higher than the remarkably constant maximum frequency at ~10 Hz observed in all black hole binaries. The key aspect of our model, which makes it match these observations, is the precession of a radially extended region of the hot inner flow. The outer radius is set by the truncation radius of the disc as above, but the inner radius lies well outside of the last stable orbit at the point where numerical simulations show that the density drops off sharply for a misaligned flow. Physically motivated analytic estimates for this inner radius show that it increases with a*, decreasing the expected frequency in a way which almost completely cancels the expected increase with spin, and ties the maximum predicted frequency to around 10 Hz for all a*. This is the first QPO model which explains both frequencies and spectrum in the context of a well-established geometry for the accretion flow.

We test the truncated disc models using multiwavelength (optical/ultraviolet/X-ray) data from the 2005 hard state outburst of the black hole Swift J1753.5−0127. This system is both fairly bright and has fairly low interstellar absorption, so gives one of the best data sets to study the ...

... Matthew Middleton,; Chris Done. ... s −1 implies 1 < L/L Edd < 4. This is supported by the distinctive nature of the optical/ultraviolet/X-ray spectral energy ... a dim, harder, low/hard state to a bright, softer low/hard state, through to the hard intermediate state (Belloni, Méndez & Homan ...