MARC details
| 000 -LEADER |
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| fixed length control field |
04912nam a2200241Ia 4500 |
| 003 - CONTROL NUMBER IDENTIFIER |
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| control field |
IN-BaIIA |
| 005 - DATE AND TIME OF LATEST TRANSACTION |
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| control field |
20211110155027.0 |
| 008 - FIXED-LENGTH DATA ELEMENTS--GENERAL INFORMATION |
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| fixed length control field |
211028s9999 xx 000 0 eng d |
| 040 ## - CATALOGING SOURCE |
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| Transcribing agency |
IIA Library |
| 100 ## - MAIN ENTRY--PERSONAL NAME |
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| Personal name |
Priyanka Rani |
| 9 (RLIN) |
37289 |
| Relator term |
Author |
| 245 #0 - TITLE STATEMENT |
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| Title |
Temporal and spectral characteristics of active galactic nuclei in x-rays using NuSTAR |
| Remainder of title |
a thesis submited for the degree of doctor of philosophy in the department of physics, Pondicherry University, Puducherry |
| Statement of responsibility, etc. |
Priyanka Rani |
| Medium |
[Ph.D Thesis] |
| 260 ## - PUBLICATION, DISTRIBUTION, ETC. |
|---|
| Place of publication, distribution, etc. |
Bangalore |
| Name of publisher, distributor, etc. |
Indian Institute of Astrophysics |
| Date of publication, distribution, etc. |
2019 |
| 300 ## - PHYSICAL DESCRIPTION |
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| Extent |
xiii, 112p. |
| 502 ## - DISSERTATION NOTE |
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| Degree type |
Doctor of Philosophy |
| Name of granting institution |
Indian Institute of Astrophysics, Bangalore |
| Year degree granted |
2019 |
| 520 ## - SUMMARY, ETC. |
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| Summary, etc. |
Flux variability is one of the defining characteristics of active galactic nuclei<br/><br/>(AGN). This has been known over the past six decades ever since the discov-<br/>ery of quasars in 1963. Since then AGN have been observed for flux variability<br/><br/>over all accessible wavelengths on a range of timescales from hours to days and<br/>months. Studying flux variability of AGN is important as it is a effective tool to<br/>probe the central regions of AGN that are not accessible by any current imaging<br/>techniques set by Rs < c×tvar, where tvar is the time scale of variability and Rs<br/>is the size of the emitting region. Of all the wavelengths that are used to probe<br/>AGN, hard X-ray is very important, because firstly it is known to originate in the<br/>immediate vicinity of the central supermassive black hole (SMBH) and secondly,<br/>it is less affected by absorption. However, available studies on the hard X-ray<br/>variability characteristics of different classes of AGN on hour like timescale is very<br/>limited.<br/><br/>The primary X-ray emission in AGN is believed to originate in a compact region<br/>called the corona situated very close to the SMBH and the accretion disk. The<br/>knowledge of the cut-off energy (Ecut) of the primary X-ray continuum in AGN is<br/>very important as it carries information on the physical characteristics of the hot<br/>X-ray emitting corona. Though Ecut has been measured in AGN in the past, the<br/>existing measurements have large error bars largely attributed to the sensitivity<br/>of the instruments used to carry out the observations. The availability of a new<br/><br/>hard X-ray focussing instrument Nuclear Spectroscopic Telescope Array (NuS-<br/>TAR) which is about 100 times more sensitive than earlier hard X-ray missions<br/><br/>has opened up the possibility to explore both the hard X-ray variability charac-<br/>teristics of AGN as well as to obtain precise Ecut values on a large sample of AGN to infer their coronal properties. Exploiting the high sensitivity of NuSTAR to<br/>observations in the 3−79 keV band, we in this thesis work aimed to address two<br/>problems (a) to carry out a comparative analysis of the hard X-ray flux variability<br/>characteristics of different classes of AGN to look for similarities and/or differences<br/>in the hard X-ray variability characteristics of radio-loud vis-a-vis radio-loud AGN<br/>on hour like time scales and (b) determine new Ecut values for a sample of AGN<br/>to infer the coronal properties and look for correlations if any between Ecut and<br/>other physical properties of AGN.<br/><br/>The first part of the thesis objective is addressed in Chapter 3, wherein we have<br/>analysed 557 sets of observations pertaining to 335 AGN that comprises of 24 BL<br/>Lac objects, 24 flat spectrum quasars (FSRQs), 20 Narrow Line Seyfert 1 galaxies,<br/>121 Seyfert 1 galaxies and 146 Seyfert 2 galaxies. Our analysis indicates that on<br/>hour like time scales, blazars (that includes FSRQs and BL Lac objects) are more<br/>variable that their radio-quiet counterparts namely the Seyfert galaxies, which<br/>could be attributed to the contribution of relativistic jets to the observed X-ray<br/>emission in blazars. We also found brighter AGN to be less variable as well as<br/>AGN powered by more massive black holes to be less variable.<br/><br/>The second part of the thesis objective is addressed in two chapters, namely Chap-<br/>ter 4 and Chapter 5. In Chapter 4, we report the first time measurement of Ecut<br/><br/>value for the radio-loud AGN, namely 3C 120, whereas in Chapter 5, we report<br/>first time measurement of Ecut values for nine AGN and an upper limit of one<br/>AGN. Combining our new Ecut measurements with those available in literature,<br/><br/>totalling 30 AGN, we found that the correlation between Ecut and the photon in-<br/>dex of AGN is complicated, thereby requiring more Ecut measurements on a large<br/><br/>number of AGN in the future to understand the complicated behaviour between<br/>Ecut and photon index.<br/> |
| 650 ## - SUBJECT ADDED ENTRY--TOPICAL TERM |
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| Topical term or geographic name entry element |
Galaxies: active |
| 9 (RLIN) |
37290 |
| 650 ## - SUBJECT ADDED ENTRY--TOPICAL TERM |
|---|
| Topical term or geographic name entry element |
Galaxies: seyfert |
| 9 (RLIN) |
37291 |
| 650 ## - SUBJECT ADDED ENTRY--TOPICAL TERM |
|---|
| Topical term or geographic name entry element |
Galxies: nuclei |
| 9 (RLIN) |
37292 |
| 650 ## - SUBJECT ADDED ENTRY--TOPICAL TERM |
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| Topical term or geographic name entry element |
X-rays: general |
| 9 (RLIN) |
37293 |
| 700 ## - ADDED ENTRY--PERSONAL NAME |
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| Personal name |
Stalin C. S. |
| Relator term |
Supervisor |
| 9 (RLIN) |
48866 |
| 856 ## - ELECTRONIC LOCATION AND ACCESS |
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| Uniform Resource Identifier |
<a href="http://prints.iiap.res.in/handle/2248/7527">http://prints.iiap.res.in/handle/2248/7527</a> |
| Link text |
Click Here to Access eThesis |
| 942 ## - ADDED ENTRY ELEMENTS (KOHA) |
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| Koha item type |
Thesis & Dissertations |
| Source of classification or shelving scheme |
Universal Decimal Classification |
