Academic Journal
Preprint typeset using L ATEX style emulateapj v. 03/07/07 PROBING THE ACCRETION DISK AND CENTRAL ENGINE STRUCTURE OF NGC 4258 WITH SUZAKU AND XMM-NEWTON OBSERVATIONS
| العنوان: | Preprint typeset using L ATEX style emulateapj v. 03/07/07 PROBING THE ACCRETION DISK AND CENTRAL ENGINE STRUCTURE OF NGC 4258 WITH SUZAKU AND XMM-NEWTON OBSERVATIONS |
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| المؤلفون: | Christopher S. Reynolds, Michael A. Nowak, Sera Markoff, Jack Tueller, Joern Wilms, Andrew J |
| المساهمون: | The Pennsylvania State University CiteSeerX Archives |
| المصدر: | http://arxiv.org/pdf/0810.2543v1.pdf. |
| سنة النشر: | 2008 |
| المجموعة: | CiteSeerX |
| الوصف: | We present an X-ray study of the low-luminosity active galactic nucleus (AGN) in NGC 4258 using data from Suzaku, XMM-Newton, and the Swift/BAT survey. We find that signatures of X-ray reprocessing by cold gas are very weak in the spectrum of this Seyfert-2 galaxy; a weak, narrow fluorescent-Kα emission line of cold iron is robustly detected in both the Suzaku and XMM-Newton spectra but at a level much below that of most other Seyfert-2 galaxies. We conclude that the circumnuclear environment of this AGN is very “clean ” and lacks the Compton-thick obscuring torus of unified Seyfert schemes. From the narrowness of the iron line, together with evidence for line flux variability between the Suzaku and XMM-Newton observations, we constrain the line emitting region to be between 3 × 10 3 rg and 4 × 10 4 rg from the black hole. We show that the observed properties of the iron line can be explained if the line originates from the surface layers of a warped accretion disk. In particular, we present explicit calculations of the expected iron line from a disk warped by Lens-Thirring precession from a misaligned central black hole. Finally, the Suzaku data reveal clear evidence for large amplitude 2–10keV variability on timescales of 50ksec as well as smaller amplitude flares on timescales as short as 5–10ksec. If associated with accretion disk processes, such rapid variability requires an origin in the innermost regions of the disk (r ≈ 10rg or less). Analysis of the difference spectrum between a high- and low-flux state suggests that the variable component of the X-ray emission is steeper and more absorbed than the average AGN emission, suggesting that the primary X-ray source and absorbing screen have spatial structure on comparable scales. We note the remarkable similarity between the circumnuclear environment of NGC 4258 and another well-studied low-luminosity AGN, M81*. |
| نوع الوثيقة: | text |
| وصف الملف: | application/pdf |
| اللغة: | English |
| Relation: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.244.6841; http://arxiv.org/pdf/0810.2543v1.pdf |
| الاتاحة: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.244.6841 http://arxiv.org/pdf/0810.2543v1.pdf |
| Rights: | Metadata may be used without restrictions as long as the oai identifier remains attached to it. |
| رقم الانضمام: | edsbas.BAAC7268 |
| قاعدة البيانات: | BASE |
| الوصف غير متاح. |