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X-Ray Studies of Highly Magnetized Neutron Stars and Their Environs

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X-Ray Studies of Highly Magnetized Neutron Stars and Their Environs X-ray studies of highly magnetized neutron stars and their environs Harsha Sanjeev Kumar A thesis submitted to the Faculty of Graduate Studies of The University of Manitoba in partial fulfillment of the requirements of the degree of Doctor of Philosophy Department of Physics and Astronomy University of Manitoba Winnipeg, Canada Copyright (c) 2013 by Harsha S. Kumar Abstract Supernova explosions are among the most energetic events known in the universe, leaving supernova remnants (SNRs) as their relics. The cores of massive stars collapse to form neutron stars, among the most compact and strongest magnets in the cosmos. The thesis studies a sample of such magnetic “beauties” in X-rays, the magnetars and high-magnetic field pulsars (HBPs), with the motivation to understand their evolutionary links. We also address the connection between these sources by investigating their environs through their securely associated SNRs. Magnetars have ultra-high magnetic fields B 1014 ∼ – 1015 Gauss (G) and include the soft-gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs). The HBPs have magnetic fields B 1013 – 1014 G, intermediate between ∼ the classical rotation-powered pulsars (B 1012 G) and magnetars. ∼ We focussed on two HBPs: J1119–6127 and J1846–0258, with similar spin-properties and associated with the SNRs G292.2–0.5 and Kes 75, respectively. In our studies, magnetar-like behavior was discovered from the Crab-like pulsar J1846–0258, clearly es- tablishing a connection between the HBPs and magnetars for the first time, while no such behavior has been observed from PSR J1119–6127 so far. J1119–6127’s overall X- ray properties together with its compact pulsar wind nebula resemble more the classical rotation-powered pulsars. We studied two magnetars, one from each sub-class: SGR 0501+4516 and AXP 1E 1841–045. The spectral and statistical analysis of the bursts and the persistent X-ray emission properties observed from them were found consistent with the magnetar model predictions as well as those seen in other SGRs. Finally, we iii probed the environment of these stellar magnets by performing a detailed X-ray imaging and spatially resolved spectroscopic study of two SNRs: G292.2–0.5 and Kes 73 associ- ated with J1119–6127 and 1E 1841–045, respectively. We found that both SNRs point to very massive progenitors (&25 solar masses), further supporting the growing evidence for magnetars originating from massive progenitors using other multiwavelength studies. Acknowledgements At this moment when I am winding up my Ph.D. thesis, I would like to thank my thesis supervisor, Dr. Samar Safi-Harb, who was kind enough to accept me as her student from the other side of the world. I am grateful for all her help, guidance, enduring encouragement, and the patience she has shown towards me. I have also been greatly benefited from all the scientific discussions with her, that have increased my curiosity and interest in this challenging field. Her positive attitude and the incredible dedication she has towards her family, Astro-group, and the research field are inspiring in many ways. Thanks to all my friends and members (past and present) of our small Astro-group at the University of Manitoba. Thanks to Heather for being a good friend and helping me with issues related to science, as well as for all the fun trips (conference, hiking) we had. Thanks to Adam Rogers for carefully reading my thesis and providing feedback. A special thanks to Maiko Langelaar for computer support as well as looking promptly into any astronomy software related issues I had encountered. Thanks also to Susan Beshta and Wanda Klassen for all their help and making my life easier here as an international student. I am greatly indebted to my husband, for being with me through thick and thin, motivating and supporting my dreams and aspirations. None of this would have been possible without him. I would like to thank my parents for their unconditional love and support, for believing in me, and for all that they have done for me. Thanks also to my sister and brother for being there for me always. v The research presented in this thesis has been been generously funded by the Natural Science and Engineering Research Council of Canada (NSERC). The work presented in this thesis has made use of state of the art facilities: Chandra X-ray Observatory operated by the National Aeronautics and Space Administration (NASA), the XMM-Newton oper- ated by the European Space Agency (ESA), and Swift gamma-ray observatory operated by an international consortium from the United States, United Kingdom, and Italy. For my dearest Mom and Dad Preface Statement of Originality The results presented in this thesis, based on the X-ray observations of highly magnetized neutron stars and associated supernova remnants, are original work that was, or will be, published in the following refereed articles, as given below. Chapter 3 Kumar, H. S., & Safi-Harb, S., Variability of the high magnetic field X-ray pulsar J1846–0258 associated with the SNR Kes 75 as revealed by the Chandra X-ray observatory, Astrophysical Journal Letters, 678, 43–46, 2008. Chapter 4 Safi-Harb, S., & Kumar, H. S. Using Chandra to Unveil the High-Energy Properties of the High Magnetic Field Radio Pulsar J1119–6127, Astrophysical Journal, 684, 532–541, 2008. Chapter 5 Kumar, H. S., Ibrahim, A. I., & Safi-Harb, S., Swift-BAT observations of the recently discovered magnetar SGR 0501+4516, Astrophysical Journal, 716, 97–105, 2010. Chapter 6 Kumar, H. S., & Safi-Harb, S., Swift study of the first SGR-like burst from AXP 1E 1841–045 in SNR Kes 73, Astrophysical Journal Letters, 725, 191–195, 2010. Chapter 7 Kumar, H. S., Safi-Harb, S., & Gonzalez, M. E., Chandra and XMM-Newton vi studies of the SNR G292.2–0.5 associated with the pulsar J1119–6127, Astrophysical Journal, 754, 96–110, 2012. Chapter 8 Kumar, H. S., Safi-Harb, S., Slane, P. O., & Gotthelf, E. V., Chandra and XMM-Newton imaging and spectroscopic study of the supernova remnant Kes 73, Astrophysical Journal: #ApJ90717, under revision, 2013. Contribution of Authors I would like to specify my contributions and acknowledge the contributions of my co- authors in the manuscripts listed above. The data presented in this thesis were reduced and analyzed by myself using the software provided by the operating centers of Chandra, XMM-Newton, and Swift observatories. All the manuscripts given above (except for Safi- Harb & Kumar 2008; see below) are mostly written by me, with contributions towards the content and publication of all manuscripts from my supervisor Samar Safi-Harb. She also provided invaluable suggestions all throughout and played a significant role in interpreting the results presented here. Chapter 4 (Safi-Harb & Kumar, 2008) Samar Safi-Harb was the principal investigator of the Chandra proposal for the high-magnetic field pulsar J1119–1627. The paper was entirely written by her, with myself contributing to the data reduction and analysis of the pulsar. The paper is included in this thesis to compare the pulsar’s X-ray properties with J1846–0258, a pulsar with similar spin properties but that showed a magnetar-like behavior. Chapter 5 (Kumar, Ibrahim, & Safi-Harb, 2010) Alaa Ibrahim proposed to study this SGR with Swift archival data. He provided valuable comments on the data analysis and suggestions on the manuscript. vii Chapter 6 (Kumar, Safi-Harb, & Gonzalez, 2012) Marjorie Gonzalez performed the archival XMM-Newton data reduction of SNR G292.2–0.5, which was used along with the Chandra data reduction performed by myself. She also provided valuable comments on the manuscript. Samar Safi-Harb was the principal investigator for the Chandra data presented in this study. Chapter 8 (Kumar, Safi-Harb, Slane, & Gotthelf, 2013) This paper made use of archival Chandra and XMM-Newton data. Patrick Slane was the principal investigator for one of the Chandra proposals for SNR Kes 73. He provided constructive comments and input for improving the manuscript and in the interpretation of the results. Eric Gotthelf was the principal investigator of the XMM-Newton proposal for SNR Kes 73, and provided valuable comments and suggestions on the manuscript. Contents Abstract ii Acknowledgements iv Preface v List of Figures xii List of Tables xiv List of Abbreviations xviii 1 Introduction 2 1.1 Supernovaeandtheirremnants . .. 2 1.1.1 Supernovaclassification . 3 1.1.2 Core-collapse supernova explosions . .... 4 1.1.3 Supernova remnants and their evolution . ... 6 1.2 Pulsars and pulsar wind nebulae . ... 10 1.2.1 Rotation-powered pulsars and observed properties . ........ 13 1.2.2 Pulsar wind nebulae (PWNe) . 15 1.3 Magnetars.................................... 16 1.3.1 Softgammarepeaters(SGRs) . 17 1.3.2 Anomalous X-ray pulsars (AXPs) . 19 1.3.3 Themagnetarmodel .......................... 21 1.4 High-magnetic field pulsars (HBPs) . .... 24 1.5 ProgenitorsofHBPsandmagnetars. ... 25 1.6 Thesismotivationandoutline . ... 27 Bibliography ..................................... 30 2 X-ray emission processes and observatories 35 2.1 Introduction................................... 35 2.2 X-rayemissionprocesses . .. 36 2.2.1 Bremsstrahlung ............................. 37 2.2.2 Lineemission .............................. 38 2.2.3 Blackbodyradiation . .. .. .. 39 CONTENTS ix 2.2.4 Synchrotronemission. 40 2.3 X-rayobservatories .............................. 42 2.3.1 Chandra ................................. 43 2.3.2 XMM-Newton .............................. 45 2.3.3 Swift ................................... 46 Bibliography ..................................... 47 3 Magnetar-like behavior from the high-magnetic field pulsar J1846–0258 50 3.1 Introduction................................... 51 3.2 Observations&ImagingResults . ... 52 3.3 Spectroscopy of PSR J1846 0258anditsPWN ............... 54 − 3.4 Discussion.................................... 57 3.4.1 X-ray variability of PSR J1846 0258................. 57 3.4.2 Comparison with the HBP PSR− J1119 6127............. 58 − 3.5 Conclusions ................................... 60 Bibliography ..................................... 61 4 X-ray properties of the high-magnetic field pulsar J1119–6127 in SNR G292.2–0.5 63 4.1 Introduction..................................
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