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Download Version of Record (PDF / 6MB) Open Research Online The Open University’s repository of research publications and other research outputs The Formation and Evolution of Cataclysmic Variables Thesis How to cite: Davis, Philip (2009). The Formation and Evolution of Cataclysmic Variables. PhD thesis The Open University. For guidance on citations see FAQs. c 2009 The Author https://creativecommons.org/licenses/by-nc-nd/4.0/ Version: Version of Record Link(s) to article on publisher’s website: http://dx.doi.org/doi:10.21954/ou.ro.0000f236 Copyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyright owners. For more information on Open Research Online’s data policy on reuse of materials please consult the policies page. oro.open.ac.uk e-p> Faculty of Science, The Open University The Formation and Evolution of Cataclysmic Variables Philip Davis MPhys. Submitted for the degree of Doctor of Philosophy June 2009 T>ecr€ <yf Suamission ; i=i Jotoe 2 ^rr£ op B S ProQuest Number: 13837663 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest 13837663 Published by ProQuest LLC(2019). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 CONTENTS LIST OF FIGURES iv LIST OF TABLES vii ABSTRACT viii ACKNOWLEDGEMENTS ix I Background and Context 1 1 Introduction 2 1.1 Mass Transfer In Binary Systems ........................................................................... 5 1.1.1 The Roche Model ........................................................................................... 5 1.1.2 Driving Mass Transfer ..................................................................................... 10 1.1.3 Mass Transfer S ta b ility .................................................................................. 11 1.2 Evolution of the Binary Parameters ........................................................................ 15 1.2.1 Orbital Parameters ........................................................................................... 15 1.2.2 Evolution of the Donor’s Stellar and Roche Lobe R adius ......................... 19 2 The Evolution of Cataclysmic Variables 26 2.1 Magnetic Braking................................................................................................................27 2.2 Parameterised Modelling of Magnetic Braking ............................................................29 2.3 The Orbital Period Distribution of the Observed CV P o p u la tio n ..........................31 2.3.1 The Period Gap and the Disrupted Magnetic Braking Hypothesis . 32 2.3.2 The Period M axim um .......................................................................................... 36 2.3.3 The Period M in im u m ..........................................................................................37 2.4 Caveats With the Standard Evolutionary P ictu re ......................................................................................................... 40 2.4.1 The Strength of Magnetic B rak in g .................................................................. 40 2.4.2 The Disruption of Magnetic B raking ................................................................ 42 2.4.3 An Alternative to the Disrupted Magnetic Braking M o d e l? ......................45 2.5 Testing the Disruption of Magnetic B ra k in g ............................................................................................................................ 46 3 The Common Envelope Phase 48 3.1 Formation of the Common E n velop e ........................................................................ 49 3.2 Common Envelope E volu tion ..................................................................................... 51 3.2.1 Rapid In-Fall P h a s e ......................................................................................... 51 3.2.2 Termination of the CE P h a s e ......................................................................... 54 3.3 Modelling of the Common Envelope Phase ...................................................................56 3.4 The Pre-CV P h a s e ............... 62 3.4.1 Subdwarf-main sequence binaries .......................................................................64 3.4.2 WD+MS Binaries via Stable Roche Lobe Overflow ...................................................................................................................64 4 Population Synthesis 66 4.1 Our Population Synthesis C o d e ................................................................................. 67 4.2 Calculating the Population ............................................................................................68 4.2.1 Formation R a t e s ................................................................................................ 70 4.2.2 The Present Day Population ............................................................................. 74 II Testing the Disruption of Magnetic Braking 77 5 Method 78 5.1 Modifications made to B iS E P S ................................................................................. 79 5.1.1 Mass Transfer in C V s ...................................................................................... 79 5.1.2 The Period Gap and Period Gap E volu tion ................................................... 86 5.2 Treatment of the CE P h a s e ............................................................................................94 6 Results and Analysis 97 6.1 Varying c* ce' Models hA to h C E 5 ...............................................................................99 6.1.1 The gPCEB P opulation ....................................................................................... 99 6.1.2 The dCV Population ............................................................................................102 6.1.3 Overall T ren d s ......................................................................................................109 6.2 oce as a function of Secondary Mass:models hPWR05 to h P W R 2 .................... 110 6.2.1 The gPCEB Population ............................................................................110 6.2.2 The dCV Population ............................................................................................I l l 6.2.3 Overall T ren d s ......................................................................................................112 6.3 Alternative Magnetic Braking Laws: Models rvj2A and rv j4 A .............................. 113 6.4 Discussion .......................................................................................................................... 114 6.4.1 Observational Predictions .................................................................................. 114 6.4.2 The Location of the Period Gap ............................................................. 115 6.4.3 An Extra Sink of Angular Momentum for Fully Convective Stars? . 116 6.4.4 Thermal Timescale Mass Transfer Sy s te m s ................................................... 118 6.4.5 Magnetic CVs ......................................................................................................118 6.4.6 PCEB C andidates ............................................................................................... 119 6.5 Conclusions ....................................................................................................................... 120 iii III A Comprehensive Population Synthesis Study of PCEBs 122 7 Method 123 7.1 The Initial Population ...................................................................................................124 7.2 Treatment of the CE P h a s e ......................................................................................... 125 7.3 The CE phase in terms of the binary’s angular momentum ....................................127 7.4 Magnetic Braking....................................................................................... 128 7.5 The Evolution of Subdwarf-Main Sequence Binaries..............................................................................................................129 7.6 Reconstructing the CE P h a s e ...................................................................................... 131 8 Results and Analysis 135 8.1 White dwarf-main sequence s y s te m s ..........................................................................136 8.2 Subdwarf-main sequence star b in a r ie s ...................................................................... 143 8.3 The shape of the distributions ...................................................................................... 147 8.4 The present day population and space densities of P C E B s .................................. 149 8.5 IK Peg: A Clue to the CE Mechanism?........................................................................................................................150 8.6 Reconstruction of the CE phase for observed P C E B s ..............................................155 8.6.1 The M 2 — l o g 10a c E p la n e .................................................................................156
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