Library Declaration and Deposit Agreement
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Library Declaration and Deposit Agreement 1. STUDENT DETAILS Gregory Charles Brown 1258033 2. THESIS DEPOSIT 2.1 I understand that under my registration at the University, I am required to deposit my thesis with the University in BOTH hard copy and in digital format. The digital version should normally be saved as a single pdf file. 2.2 The hard copy will be housed in the University Library. The digital ver- sion will be deposited in the Universitys Institutional Repository (WRAP). Unless otherwise indicated (see 2.3 below) this will be made openly ac- cessible on the Internet and will be supplied to the British Library to be made available online via its Electronic Theses Online Service (EThOS) service. [At present, theses submitted for a Masters degree by Research (MA, MSc, LLM, MS or MMedSci) are not being deposited in WRAP and not being made available via EthOS. This may change in future.] 2.3 In exceptional circumstances, the Chair of the Board of Graduate Studies may grant permission for an embargo to be placed on public access to the hard copy thesis for a limited period. It is also possible to apply separately for an embargo on the digital version. (Further information is available in the Guide to Examinations for Higher Degrees by Research.) 2.4 (a) Hard Copy I hereby deposit a hard copy of my thesis in the University Library to be made publicly available to readers immediately. I agree that my thesis may be photocopied. (b) Digital Copy I hereby deposit a digital copy of my thesis to be held in WRAP and made available via EThOS. My thesis can be made publicly available online. 3. GRANTING OF NON-EXCLUSIVE RIGHTS Whether I deposit my Work personally or through an assistant or other agent, I agree to the following: Rights granted to the University of Warwick and the British Library and the user of the thesis through this agreement are non- exclusive. I retain all rights in the thesis in its present version or future ver- sions. I agree that the institutional repository administrators and the British Library or their agents may, without changing content, digitise and migrate the thesis to any medium or format for the purpose of future preservation and accessibility. 4. DECLARATIONS (a) I DECLARE THAT: I am the author and owner of the copyright in the thesis and/or I have • the authority of the authors and owners of the copyright in the thesis to make this agreement. Reproduction of any part of this thesis for teaching or in academic or other forms of publication is subject to the normal limitations on the use of copyrighted materials and to the proper and full acknowledgement of its source. The digital version of the thesis I am supplying is the same version • as the final, hardbound copy submitted in completion of my degree, once any minor corrections have been completed. I have exercised reasonable care to ensure that the thesis is original, • and does not to the best of my knowledge break any UK law or other Intellectual Property Right, or contain any confidential material. I understand that, through the medium of the Internet, files will be • available to automated agents, and may be searched and copied by, for example, text mining and plagiarism detection software. (b) IF I HAVE AGREED (in Section 2 above) TO MAKE MY THESIS PUB- LICLY AVAILABLE DIGITALLY, I ALSO DECLARE THAT: I grant the University of Warwick and the British Library a licence to • make available on the Internet the thesis in digitised format through the Institutional Repository and through the British Library via the EThOS service. If my thesis does include any substantial subsidiary material owned • by third-party copyright holders, I have sought and obtained permis- sion to include it in any version of my thesis available in digital format and that this permission encompasses the rights that I have granted to the University of Warwick and to the British Library. 5. LEGAL INFRINGEMENTS I understand that neither the University of Warwick nor the British Library have any obligation to take legal action on behalf of myself, or other rights holders, in the event of infringement of intellectual property rights, breach of contract or of any other right, in the thesis. Please sign this agreement and return it to the Graduate School Office when you submit your thesis. Student's signature: ..................................Date: ................. A Study of Exotic Nuclear Extragalactic Transients by Gregory Charles Brown Thesis Submitted to the University of Warwick for the degree of Doctor of Philosophy Department of Physics September 2016 Contents List of Tables iv List of Figures v Acknowledgments vii Declarations viii Abstract ix Chapter 1 Introduction 1 1.1 The Study of an Ever-changing Universe . .1 1.2 An Introduction to Black Holes . .3 1.2.1 Supermassive Black Holes . .6 1.3 Active Galactic Nuclei . 10 1.3.1 Background . 11 1.3.2 AGN Variability . 15 1.3.3 Identifying Active Hosts . 19 1.4 Tidal Disruption Flares . 20 1.5 Relativistic Tidal Disruption Flares . 30 1.5.1 A connection between long-lived gamma-ray events? . 34 1.6 Supernovae . 36 1.6.1 Superluminous Supernovae . 40 1.7 Summary of Transient Properties . 41 Chapter 2 Methods and Observations 44 2.1 Detectors across the electromagnetic spectrum . 44 2.1.1 UV, Optical and Near-Infrared detectors . 44 2.1.2 X-ray and Gamma-ray detectors . 47 2.2 Reduction and Analysis Techniques . 49 i 2.2.1 Optical Image Reduction . 49 2.2.2 Optical Spectroscopic Reduction . 56 2.3 Astrometry . 58 2.3.1 Astrometric Matching . 58 2.3.2 Image Subtraction . 60 2.3.3 Modelling Galaxy Morphology and Determining Centroid Po- sitions . 61 2.4 Magnitude Systems and Cosmology . 62 Chapter 3 The Candidate Relativistic Tidal Disruption Flare Swift J1112.2-8238 64 3.1 Introduction . 64 3.2 Observations . 65 3.2.1 Swift BAT data . 65 3.2.2 X-ray data . 66 3.2.3 Optical Imaging . 67 3.2.4 Spectroscopy . 75 3.3 Discussion . 77 3.3.1 Physical properties . 77 3.3.2 Comparison to other sources . 78 3.4 Implications . 83 3.5 Summary . 87 Chapter 4 Late Time Observations of Swift J1112.2-8238 88 4.1 Introduction . 88 4.2 Observations . 89 4.2.1 HST Imaging . 89 4.2.2 X-Shooter Spectroscopy . 93 4.2.3 Late-time Radio Observations of the Host . 101 4.3 Discussion . 104 4.3.1 Host Morphology and Transient Position . 104 4.3.2 Internal Extinction . 106 4.3.3 Metallicity and Classification of the Host . 107 4.3.4 Stellar Mass and Black Hole Mass . 109 4.3.5 UV/Optical Star Formation Rate Estimates . 110 4.3.6 Properties of the Radio Emission . 111 4.4 Implications for the interpretation of the flare . 115 4.5 Summary . 118 ii Chapter 5 A Study of Four Unusual Nuclear Transients 119 5.1 Introduction . 119 5.2 Observations . 121 5.2.1 HST imaging . 121 5.2.2 CSS100217: Optical Observations . 130 5.2.3 CSS100217: Swift Observations . 130 5.3 Discussion . 135 5.3.1 Astrometry of the Transients . 135 5.3.2 Evolution of the Transients . 138 5.4 Implications for the origins of the flares . 143 5.4.1 ASASSN14ae . 143 5.4.2 ASASSN14li . 144 5.4.3 CSS100217 . 145 5.4.4 ASASSN15lh . 147 5.5 A Possible New Class of AGN flare or a Sub-Class of TDF? . 148 5.6 Summary . 151 Chapter 6 Conclusions 153 6.1 Summary of Results . 153 6.1.1 The Relativistic Tidal Disruption Flare Candidate: Swift J1112.2- 8238 . 153 6.1.2 The Late-time Analysis of Swift J1112-8238 . 155 6.1.3 An Expanding Variety of Nuclear Flares . 156 6.2 Overview and Future Prospects . 157 iii List of Tables 3.1 GMOS and FORS2 photometry of Swift J1112-8238 . 73 4.1 HST photometry of the host of Swift J1112-8238, broken down by component . 94 4.2 The emission line fluxes determined from the X-Shooter spectrum of the host of Swift J1112-8238 . 101 4.3 The radio fluxes determined from the ATCA observations of Swift J1112-8238 and Swift J2058+05 . 104 4.4 The inferred star formation rate estimates for the components of the host of Swift J1112-8238 . 111 5.1 The key features of the HST observations . 125 5.2 The HST photometry of the host and transient emission of ASASSN14ae, ASASSN14li, CSS100217 and ASASSN15lh . 128 5.3 Swift-UVOT photometry of CSS100217 . 131 5.4 The angular distances and physical offsets of the host and transient centroids for ASASSN14ae, ASASSN14li and ASASSN15lh . 137 iv List of Figures 1.1 Typical spectra of active galactic nuclei . 12 1.2 The unified model of AGN . 14 1.3 A typical multiwavelength AGN lightcurve . 17 1.4 Baldwin Phillips & Terlevich diagrams for SDSS galaxies . 21 1.5 Three possible configurations of the infall of a star towards a super- massive black hole . 23 1.6 The lightcurves of ROSAT detected tidal disruption flares . 26 1.7 Continuum subtracted spectra from a range of tidal disruption flare candidates showing a range of line strengths that indicate a variety of disrupted stars . 29 1.8 The X-ray Luminosity - Optical Absolute Magnitude phase space for a selection of extragalactic transients and AGN . 32 1.9 The T90 and hardness ratios for GRBs detected by CGRO, BATSE and Swift ................................. 35 1.10 A summary of the classes of supernovae .