|
| | | | |
| | | |
| Stat |
Members: 3665
Articles: 2'599'751
Articles rated: 2609
23 January 2025 |
|
| | | | |
|
Article overview
| |
|
|
Can the soft excess in AGN originate from disc reflection? | | Chris Done
; Sergei Nayakshin
; | | Date: |
15 Jan 2007 | | Abstract: | The soft excess seen in many AGN is most probably due to partially ionized material moving at relativistic speeds close to the black hole. There are currently two potential geometries for this material, one where it is out of the line of sight, seen via reflection, e.g. the accretion disc, the other where it is in the line of sight, seen in absorption e.g. a wind above the disc. Both models require apparent fine tuning of the ionization parameter of this material in order to produce the large jump in opacity at ~0.7 keV associated with OVII/VIII, as required to make the soft excess. However, Chevalier et al (2006) show that these states rather naturally dominate the absorption spectrum for soft X-ray spectra if the illuminated material is (at least approximately) in pressure balance. Here we explore whether hydrostatic pressure equilibrium in a disc can likewise naturally select the required ionization states in reflection. We find the opposite. The soft excess X-ray excess is much weaker in the hydrostatic models than it is in the constant density models. Since even the constant density models cannot fit the largest soft excesses seen without the intrinsic continuum being hidden from view, this means that reflection from a hydrostatic disc cannot realistically match the data. Even if the disc structure is instead more like constant density atmosphere, the required fine-tuning of the ionization parameter still remains a problem, making this also an unlikely explanation for the soft excess. | | Source: | arXiv, astro-ph/0701410 | | Services: | Forum | Review | PDF | Favorites | |
|
|
No review found.
Did you like this article?
Note: answers to reviews or questions about the article must be posted in the forum section.
Authors are not allowed to review their own article. They can use the forum section.
|
| |
|
|
|
REGISTER