Post-graduate theses
Current Record: 4989 of 6513
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| Identifier |
000381526 |
| Title |
A study of the iron line variability in the X-Ray spectrum of active galaxy MCG-6-30-15 |
| Alternative Title |
Μελέτη μεταβλητότητας της γραμμικής σιδήρου στο φάσμα ακτίνων Χ του ενεργού γαλαξία MCG-6-30-15 |
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Author
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Επιτροπάκης, Αναστάσιος
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Thesis advisor
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Παπαδάκης, Ιωσήφ
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| Abstract |
To this day, the geometry of the inner-most region of active galaxies remains unknown. A promising (and perhaps the only) way to indirectly probe this region is through X-ray variability studies. Observations reveal the presence of a strong emission line centered at 6.4 keV, interpreted as Fe Kα emission, in the X-ray spectra of active galaxies. This has led to the formulation of the so-called "illuminated disc" hypothesis, according to which the Fe line arises due to emission from a "primary" X-ray source being reflected by an accretion disc. In many cases, the profile of the Fe K$alpha$ line is found to be broad (~5-6.6 keV) and "skewed" towards longer wavelengths, which is indicative of material orbiting close to a black hole.
The above facts stimulated an ongoing attempt to identify and study correlations, in the form of temporal delays, between light-curves that are thought to represent "reflected" (traditionally identified with the 0.5-1.5 keV band) and "primary" (traditionally identified with the 2-4 keV band) emission components envisaged in an "illuminated disc" scenario. Studies of such delays have so far indicated that the data are consistent with an "illuminated disc" scenario in its simplest form.
In this work I focused my attention on a particular active galaxy, MCG-6-30-15, since (a) it was the first one for which a broad Fe Kα line was observed, (b) it is a bright source of X-rays, and (c) it has been observed by many satellites. I collected all available data from both the Suzaku and XMM-Newton X-ray satellites. This is the first time that data from the former satellite has been used to estimate delays. The purpose of my work is, first of all, to use estimates from both satellites in order to constrain the delays between the "reflected" and "primary" emission that have already been observed in MCG-6-30-15, and secondly to estimate, for the first time, the delays between the Fe Kα line itself (which is expected to be a clearer signature of reflection than the traditionally used 0.5-1.5 keV band) and the ``primary" emission. My results indicate that the delays between the line and the "primary" X-ray source are not consistent with a simple "reflection scenario", while it remains unclear whether Suzaku and XMM-Newton data can be reliably combined in order to constrain the delays.
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| Language |
English |
| Subject |
X-rays |
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Ακτίνες-Χ |
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Ενεργός γαλαξίας |
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Μεταβλητότητα |
| Issue date |
2013-11-15 |
| Collection
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School/Department--School of Sciences and Engineering--Department of Physics--Post-graduate theses
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Type of Work--Post-graduate theses
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| Permanent Link |
https://elocus.lib.uoc.gr//dlib/f/1/d/metadata-dlib-1387278761-545352-15697.tkl
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| Views |
577 |
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