Devon Hamilton

Devon Hamilton A Thesis submitted in conformity with the requirements for the Degree of Doctor of Philosophy. Graduate Department of -4stronomy and Astrophysics, in the University of Toronto. @ Copyright by Devon Hamilton 2001 National Libraiy Bibliothèque nationale 191 of Canada du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellington Street 395. nie Wellington Ottawa ON K1A ON4 Ottawa ON K1A ON4 Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant a la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distnbute or sell reproduire, prêter, distribuer ou copies of this thesis in rnicroform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/film, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protege cette thèse. thesis nor substantid extracts fiom it Ni la thèse ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author' s ou autrement reproduits sans son permission. autorisation. Observational Signatures of Convection in Solar Type Stars Doctor of Philosophy, 2001 Devon Harnilt on Graduate Department of .4stronomy and Astrophysics University of Toronto Abstract In t his t hesis. a new technique for studying convection is developed using relative line-shifts. The technique is tested using the sun's visible flu spectrum and the most current Fe 1line positions anilable. and cm be applied at significant ly lotver spectral resolut ions and signal- to-noise ratios than has been done previously. These line-shifts show a clear dependence on both line srrmgrh and wavelengt h. Similar observations in the solar intensity spectrum dernons trate t hat the rffects of limb darkening on the line-shifts are relatively minor. Because the solar intensity spectriim tias ben observed well into the infrared, it has been rised to itudy the lineshift techniqiies over the broadest possible spectral region. The Fe 1 Iiiie-core shift distributions show clear evidence of a clependence on line strength at al1 wavelengt hs. and sensi tivities to wavelengtli are foiind at sliorter wwelengths. Line-shifts for 1323 CO lines betteen 2.2 and 5.5 prn are also deterinined. Clear evidence of a dependence on line strength is found at al1 wavelengths. and interesting linc-shift behavior is found when the excitation energy and quantum nurnbers of the CO transitions are examined. .A similar study of CO and OH line-shifts is done using a sunspot unibral spectrum. and the convective motions are found to be greatly suppressed. Line-shifts are also examined in the infrared spectrum of six cool giant stars. The vigorous nature of convection seerns to declirir with Thwhich is consistent with expectations. Acknowledgements To properly express my gratitude to al1 the different people who have influenced this thesis is truly a daunting task. I owe a tremendous debt to my supervisor, John Lester, who siipported and guidecl my research over the past five years. His suggestions and insight lead to some of the more interesting and useful portions of this thesis; thanks John! The initial impetus for this thesis came from both John Lester and from SIavek Rucinski, who suggested a particular review article that sparked the author's curiosity. Slavek has also proven to be a valuable critic of much of this work. and his insight is appreciated. Without the great assistance of JeamPierre Slaillard, and of course the night assistants at CFHT. it would not have been possible to complete this thesis. J.-P. provided both tecl-inical assistance with the FTS and scientific advice, which was very helpf~~l.Discussion with .Allm Irwin. Dainis Dravins and Dag Gulfberg also influenced the direction and content of this thesis. whicfi is greatly appreciated. And of course. ri. debt of gratitude is o~veclto the rcferees for the CFHT time allocation requests and the journal paper P=\SP lll:1133. much of which was incorporatcd into Chapter 2. The suggestions and comments of the referees wrc rnost valilable. Large postions of Chapter 2 originally appeared in the Publications of the .-lstronomical Society of the Pacific (Hamilton and Lester, 1999, PXSP, !11. 1132). Copyright 2000. Xstronomical Society of the Pacific; reproduced with permission of the Editors. 1 am gratefui to Chuck Shepherd for bot h his friendship and his useful suggestions. Chuck often proved hirnseif to be a strong sounding board off of him ideas could be boiinced. A special note of thanks has to be extencled to Milie Allen. who providcd a great deal of assistance the formatting and witing of this thesis, and for being an ea.y mark in the v;irioils hockey pools we have had over the years. Perhaps the greatest debt of gatitiide 1 owe is to my hmily. whose love. patience and support have carried throughout the iast 5 years. To my parents Glen and Rae, who have given me their love and support throughout this long process, a heartfelt thank you. To my children. Megan and Patrick, whose curiosity has often been an inspiration to me, 1 dedicate this thesis with al1 of my love. Last, but definitely not least. the greatest debt 1 owe is to my wife. Erin. Her love. support. patience. humor and understanding have sustained me throughout this proccss. and 1 am erernally grateN for that (goodness knows. 1 certainly did not deserve it!). Contents 1 An Introduction to Photospheric Convection 1 1.1 Background . 1 1.2 At mosp heric Convection . - . 9- 1.3 The hliuing Length Theory , . - . - . 5 1.4 Curent Approaches . 6 1.4.1 Turbulent Convection Theories . ti 1.. Xumerical Sirnuiat ions . 8 1.5 Convection and Spectral Line .Asymmetries . ID 1.6 Diagnostic Candidates . 13 2 A Technique for the Study of Stellar Convection: The Visible Solar Flux Spectrum 17 2. Introduction. - - 17 2.2 Slethodoiogy . 1s 2.2.1 Solar Flux Spectrum . 15 2.2.2 The Determination of Line Positions . 1S 2.2.3 Errors . 9-- .FI 2.3 Analysis . + . -- 2.3.1 Line-shifts . -2.2-- 2.3.2 Spectral Resolution Effects . 30 2.4 Conclusions . 37 3 Fe 1 in the Central Intensity Spectrum of the Sun 42 3.1 Introduction ......................................... 42 3.2 Methodology ........................................ 43 3.2.1 Spectral Sources .................................. 43 3.2.2 Wavelength Errors ................................. 45 3.3 LineSelection ........................................ 46 3.3.1 Fe1 .........................................46 3.3.2 Ti1 ......................................... 46 3.4 hnalysis ........................................... 47 3.4.1 F~LY-IntensityComparison ............................ 47 3.4.2 Fe1 .........................................47 3.4.3 Ti1 .........................................39 3.4.4 Summary ......................................61 3.5 Intensity Spectra ...................................... 62 3.5.1 WaveIength Dependence .............................. 62 3.5.2 Line-Depth Dependence .............................. 64 3.5.3 Excitation Enerby Dependence .......................... 67 3.5.4 Line Formation Depth ............................... 6'3 -- 3.6 Conclusions ......................................... Ia 4 CO in The Centrai Intensity Spectrum of the Sun 77 .. 4.1 Introduction ......................................... 1, 4.2 Methodology ........................................ 7S 4.2. S01a.r Intensity Spectral Atlases .......................... 7S 4.3.2 Line Selection .................................... 78 4.3.3 Errors ........................................ 79 4.3 Xndysis ........................................... 80 4.3.1 CN ....................................... $0 4.3.2 CO Av=I ..................................... S1 4.3.3 COAv=2 ..................................... 90 4.4 Discussion .......................................... 90 4.5 Conclusions ......................................... 96 7.3 Future Projects .......................................159 7.3.1 Exploring Convection in Stek Parameter Space ................159 7.3.2 Fe 1 Line-shifts at High .r1 ............................. 160 1+3.3 CO Formation -4ltitudes ..............................160 List of Tables 2.1 Fe I Visible Flku Bin Characteristics ........................... 41 6.1 Properties of Observed Stars ...............................141 6.2 CFHT Observations .................................... 6.3 CO lv=2 Distribiition Properties ............................ 1-14 vii List of Figures 1.1 Two example bisectors ................................... 11 1.2 Tracing the bisector using line-core positions ...................... I:! 2.1 Method schematic ..................................... 20 2.2 Fe 1 line-shifts vs . y1 ....................................24 2.3 Fe 1 line-shifts vs ki binned by X and line strength ................... 25 2.4 Fe 1 line-shift vs . line depth ................................ 23 2.5 Fe I line-shifts vs . wavelength ............................... '19 2.6 Fe 1 meclian bisectors .................................... 31 2 .7 Resolrition effects on Ftb I line-siiift distributions ................... 33 '?.Y Slope of Fe 1 line depth/line-siiift distributions vs . R .................. 35 2.9 Resoiution effects on Fe 1 wavelength dependence .................... 36 2.10 Cornparison to other methods ............................... 'JY 3.1 Fe 1

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