Understanding X‐ray reflection emissivity profiles in AGN: locating the X‐ray source

By D. Wilkins, A. C. Fabian. 2012

204 citations recorded by the source corpus.

The illumination pattern (or emissivity profile) of the accretion disc due to the reflection of X-rays in active galactic nucleus can be understood in terms of relativistic effects on the rays propagating from a source in a corona surrounding the central black hole, both on their trajectories and on the accretion disc itself. Theoretical emissivity profiles due to isotropic point sources as well as simple extended geometries are computed in general relativistic ray-tracing simulations performed on graphics processing units (GPUs). Such simulations assuming only general relativity naturally explain the accretion disc emissivity profiles determined from relativistically broadened emission lines which fall off steeply (with power-law indices of between 6 and 8) over the inner regions of the disc, then flattening off to almost a constant before tending to a constant power law of index 3 over the outer disc. Simulations for a variety of source locations, extents and geometries show how the emissivity profiles depend on these properties, and when combined with reverberation time lags allow the location and extent of the primary X-ray source to be constrained. Comparing the emissivity profile determined from the broadened iron K emission line in spectra of 1H 0707−495 obtained in 2008 January to theoretical emissivity profiles and applying constraints from reverberation lags suggest that there exists an extended region of primary X-ray emission located as low as 2rg above the accretion disc, extending outwards to a radius of around 30rg.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/0ede417d28735e58355a8271c5decd9b4feaaa04

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Citations in the corpus

X-ray reverberation around accreting black holes (2014, background): “The corona is inferred to extend to around 35rg over the disc in the narrow line Seyfert 1 galaxy 1H0707-495 (Wilkins & Fabian 2011, 2012) and to around 10rg in IRAS 13224-3809 (Fabian et al. 2013).”
The role of the reflection fraction in constraining black hole spin (2014, background): “Furthermore, since an extended source can be treated as the superposition of point sources (e.g., Dauser et al. 2010, 2013; Wilkins & Fabian 2012), it is easy to see that the broadening of the reflection spectrum will be dominated by the emission from the point where th flux intercepted by the disc…”
IMPROVED REFLECTION MODELS OF BLACK HOLE ACCRETION DISKS: TREATING THE ANGULAR DISTRIBUTION OF X-RAYS (2013, unknown): “In detail, for a standard Shakura & Sunyaev (1973) disk the emitted intensity behaves like I ∝ r−3, while for a disk irradiated by a source on the black hole’s rotational axis, generally, an even steeper profile is expected (e.g., Fukumura & Kazanas 2007; Wilkins & Fabian 2012; Dauser et al. 2013).”
Testing black hole candidates with electromagnetic radiation (2015, background): “Observations seem to require a high, or even very high, value of q at small radii (Wilkins & Fabian, 2011, 2012)21.”
Irradiation of an accretion disc by a jet: general properties and implications for spin measurements of black holes (2013, methodology): “The 4-velocity is then given by uµh = u t h ( 1, dr dt , 0, 0 ) (22) The velocityβ as seen by an observer at the same location in the locally non-rotating frame (LNRF) is connected todr/dt through β = e (r) µ u µ h e (t) ν uνh = r2 + a2 ∆ · dr dt , (23) where e(ν)µ are the tetrad basis vectors forν ”
The Masses and Spins of Neutron Stars and Stellar-Mass Black Holes (2014, background): “Parameters central to the blurring include the emissivity of the disk reflection spectrum (typically a power-law in radius, with zero–two breaks; see [253, 254, 255] ), and the inclination of the inner disk.”