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Radiation mechanisms of VHE gamma-ray sources (Record no. 18777)

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control field IN-BaIIA
005 - DATE AND TIME OF LATEST TRANSACTION
control field 20211112143911.0
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fixed length control field 211028s9999 xx 000 0 eng d
040 ## - CATALOGING SOURCE
Transcribing agency IIA Library
080 ## - UNIVERSAL DECIMAL CLASSIFICATION NUMBER
Universal Decimal Classification number (043.2)524.3-64
Item number SHU
100 ## - MAIN ENTRY--PERSONAL NAME
Personal name Shukla, Amit
9 (RLIN) 35924
Relator term Author
245 #0 - TITLE STATEMENT
Title Radiation mechanisms of VHE gamma-ray sources
Remainder of title a thesis submitted for the award of doctor of philosophy in department of physics, Pondicherry university, Pondicherry
Statement of responsibility, etc. Amit Shukla
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. 2013
300 ## - PHYSICAL DESCRIPTION
Extent xxiii, 164p.
500 ## - GENERAL NOTE
General note Thesis Supervisor Prof. Anupama, G. C.
502 ## - DISSERTATION NOTE
Degree type Doctor of Philosophy
Name of granting institution Pondicherry University, Puducherry
Year degree granted 2013
520 ## - SUMMARY, ETC.
Summary, etc. Active galactic nuclei (AGN) are one of the most luminous objects in the uni-verse. They are the sub-class of galaxies which emit extremely luminous emissionfrom the nuclear regions of the galaxy. This emission is spread widely across the electromagnetic spectrum from radio wavelengths to -rays. This radiation from AGN is believed to be the result of accretion of matter onto the supermassive black hole of mass 108- 1010 M⊙ at the center of the host galaxy. The AGN are classified by their random pointing directions to the observer in the unified scheme. AGN are mainly divided into three classes : (i) Seyfert galaxies, (ii) quasars and (iii) blazars.<br/>(i) Seyfert galaxies have modest luminosities and they are best studied since they generally lie near to us; (ii) quasars are more luminous than the host galaxy and found further away, and (iii) blazars are characterized by nonthermal emission ex-<br/>tending from radio to high energies. The broadband radiation originates within a relativistic jet that is oriented very close to the line of sight of the observer. The extragalactic TeV astronomy began with the detection of the nearby (z=0.031) blazar Mrk 421 above 500 GeV by the Whipple observatory [1]. Spectral energy distribution (SED) of the high energy peaked TeV blazars show two broad<br/>peaks. The first peak is located between infrared to X-ray energies and the second peak at -ray energies. It is believed that the first peak of the SED originates due to synchrotron radiation by relativistic electrons gyrating in the magnetic field of the jet. The origin of the high energy GeV/TeV peak is still under debate. This high energy peak might originate either due to interaction of electrons with photon field via Inverse Compton (IC) scattering as in leptonic models [2, 3, 4] or due to interaction of protons with matter, magnetic field [5, 6] or photon fields as in the hadronic models. The existing data from multiwavelength observations are not good enough to<br/>constrain the dominant emission mechanisms in the jet that are responsible for the high energy bump. The main reason behind this is the lack of the data in the energies from 100 MeV to hundreds of GeVs. In the past few years, ground based Atmospheric Cherenkov Telescope (>100 GeV) and the space based Fermi-LAT telescope (30 MeV- 300 GeV) have started providing data in this energy range. The multiwavelength observations from radio to very high energy (VHE) -rays have started to provide better constraints on the AGN models [7] and also enhance our understanding about the these sources. A multiwavelength study of Mrk 421 and Mrk 501 are presented in this thesis. The very high energy -ray data obtaining using HAGAR array are combined with<br/>archival data from Fermi-LAT, RXTE-ASM, Swift-BAT, Swift-XRT, RXTE-PCA, SPOL and OVRO for a multiwavelength study. The observed multiwavelength SED is explained by using a one zone homogeneous SSC model [8]. We have attempted<br/>to obtain SEDs for different flux states using multiwavelength data of Mrk 421 and Mrk 501. The evolution of SED during a giant flare in February 2010 from Mrk 421 is also studied in detail. This study of TeV blazars shows that the observed broadband<br/>SED is oriented by Synchrotron self Compton (SSC) mechanism. It also suggests that the electron population in the jet is accelerated by shocks which are present in the jets. Modeling of the flux variability from Mrk 501 is also attempted to constrain the<br/>physical properties and emission mechanisms. Recently observed minute timescale variability of Mrk 501 at TeV energies has imposed severe constraints on jet models and TeV emission mechanisms. We present a viable model to explain this fast<br/>variability. Details of HAGAR telescope array located at an altitude of 4300 m in IAO, Hanle are also presented in this thesis, with a detailed description of the instrument. In addition to the telescope system, data analysis techniques adopted to detect point<br/>sources, and the basics of atmospheric Cherenkov technique are described.
650 ## - SUBJECT ADDED ENTRY--TOPICAL TERM
Topical term or geographic name entry element Gamma-ray astronomy
9 (RLIN) 7465
650 ## - SUBJECT ADDED ENTRY--TOPICAL TERM
Topical term or geographic name entry element Radiation
9 (RLIN) 1862
650 ## - SUBJECT ADDED ENTRY--TOPICAL TERM
Topical term or geographic name entry element Thesis
9 (RLIN) 18401
700 ## - ADDED ENTRY--PERSONAL NAME
Personal name T. P. Prabhu
Relator term Supervisor
9 (RLIN) 48848
856 ## - ELECTRONIC LOCATION AND ACCESS
Uniform Resource Identifier <a href="http://prints.iiap.res.in/handle/2248/6318">http://prints.iiap.res.in/handle/2248/6318</a>
Link text Click Here to Access eThesis
942 ## - ADDED ENTRY ELEMENTS (KOHA)
Koha item type Thesis & Dissertations
Source of classification or shelving scheme Universal Decimal Classification
Holdings
Withdrawn status Lost status Source of classification or shelving scheme Damaged status Not for loan Home library Current library Shelving location Date acquired Full call number Barcode Date last seen Price effective from Koha item type
    Universal Decimal Classification     IIA Library-Bangalore IIA Library-Bangalore General Stacks 23/08/2013 (043.2)524.3-64/ SHU 19699 05/11/2021 23/08/2013 Thesis & Dissertations

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