New Methods and First Results for Deriving CNO Surface Abundances
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Atmospheric NLTE-Models for the Spectroscopic Analysis of massive stars: New methods and first results for deriving CNO surface abundances Luiz P. Carneiro Atmospheric NLTE-Models for the Spectroscopic Analysis of massive stars: New methods and first results for deriving CNO surface abundances Dissertation an der Ludwig–Maximilians–Universitat¨ (LMU) Munchen¨ Ph.D. Thesis at the Ludwig–Maximilians–University (LMU) Munich submitted by Luiz Paulo Carneiro Gama born on 23st March 1989 in Rio de Janeiro, Brazil Munich, August 22th 2018 1st Evaluator: Priv. Doz. Dr. Joachim Puls 2nd Evaluator: Prof. Dr. Barbara Ercolano Date of the oral exam: 10th October, 2018 In memory of my cousins Denis Rosman and Daniel Schwin that could not wait for me to come back home and nowadays watch and protect my steps. Contents Contents v List of Figures x List of Tables xi Zusammenfassung xiii Abstract xv 1 Introduction 1 1.1 Massive star evolution . 2 1.1.1 Phasesofevolution............................... 3 1.2 Mass loss through stellar winds . 6 1.3 CNO evolution and internal mixing . 9 1.4 Motivation of this thesis . 12 1.5 Outline of this thesis . 13 2 Atmospheric NLTE models for the spectroscopic analysis of blue stars with winds: X-ray emission from wind-embedded 2.1 Introduction....................................... 15 2.2 Implementation of X-ray emission and absorption in FASTWIND . 17 2.2.1 X-rayemission ................................. 17 2.2.2 X-ray absorption and Auger ionization . 20 2.2.3 Radiative and adiabatic cooling . 20 2.3 Modelgrid ....................................... 21 2.4 Tests........................................... 23 2.4.1 Impact of various parameters . 24 2.4.2 Scaling relations for Lx ............................. 28 2.4.3 Comparison with WM-basic models...................... 30 2.5 Results.......................................... 34 2.5.1 Ionization fractions . 35 2.5.2 Impact of Auger ionization . 46 2.5.3 Dielectronic recombination of O v ....................... 47 vi CONTENTS 2.5.4 Mass absorption coefficient........................... 50 2.6 Summary and conclusions . 58 2.A Appendix A: Ionization fractions of selected ions: Dependence on X-ray filling factor and shock temperature 2.B Appendix B: Comparison with WM-basic: Ionization fractions and UV line profiles . 67 2.C Appendix C: Averaged mass absorption coefficients: Clumped winds and dependence on averaging interval 3 Carbon line formation and spectroscopy in O-type stars 71 3.1 Introduction....................................... 72 3.2 Prerequisites for a carbon diagnostics . 74 3.2.1 Thecode .................................... 74 3.2.2 Thecarbonmodelatom ............................ 75 3.2.3 Diagnostic optical carbon lines . 78 3.2.4 Modelgrid ................................... 78 3.2.5 Observationaldata ............................... 80 3.3 Testing the atomic model . 80 3.3.1 Dielectronic recombination . 82 3.3.2 Further comparison with WM-basic ...................... 86 3.3.3 Optical carbon lines – dependence on stellar parameters . 88 3.4 First comparison with observed carbon spectra . ...... 91 3.4.1 Basic considerations . 91 3.4.2 Details on individual spectra . 94 3.4.3 Which lines to use? . 96 3.4.4 ImpactofX-rays ................................ 102 3.5 Summary and conclusions . 103 3.A Appendix A: Electronic states of each carbon ion . 107 3.B Appendix B: Dependence on stellar parameters . 110 4 Surface abundances of CNO in Galactic O-stars:A pilot study with FASTWIND 114 4.1 Introduction....................................... 115 4.2 Observations and target selection . 117 4.3 Abundance analysis: strategy . 118 4.3.1 Basic considerations . 118 4.3.2 Stellar parameters and model grids . 120 4.3.3 Diagnostic lines in the optical . 122 4.4 Analysis of CNO abundances . 124 4.4.1 Equivalent width measurements . 124 4.4.2 Which lines to use? . 125 4.4.3 χ2-minimization and error estimates . 125 4.5 Results.......................................... 128 4.5.1 Basic considerations . 128 4.5.2 Generalcomments ............................... 130 4.5.3 Microturbulence ................................ 131 CONTENTS vii 4.5.4 Stellar evolutionary models . 131 4.5.5 A consistency check – mixing-sensitive ratios . 133 4.5.6 Comparison with previous studies . 135 4.6 Comparison with evolutionary calculations . 137 4.6.1 Evolutionary stages . 138 4.6.2 CNOevolution ................................. 140 4.7 Summary, conclusions, and future work . 147 4.A Appendix A: Equivalent width measurements – three typical examples . 150 4.B Appendix B: χ2 minimization – exemplary cases . 150 4.C AppendixC:Lineprofiles ............................... 152 5 Summary and Conclusions 160 Bibliography 163 Acknowledgements 183 viii CONTENTS List of Figures 1.1 Schematic picture of the CNO cycle . 10 2.1 Emergent Eddington fluxes for model S30 and for a model with an unshocked wind . 25 2.2 Ratio of shock emissivity to total emissivity for model S30 from Fig. 2.1 with Rmin= 1.2 R 26 6 input ∗ 2.3 Emergent Eddington fluxes for model S30, with Ts∞ = 3 10 K and R = 1.5 R , for different values of fX, · min ∗ 2.4 Emergent Eddington fluxes for model S30 . 28 1 2.5 Emergent X-ray luminosities (in erg s− ) as a function of M˙ /v ............ 29 2 1 ∞ 1 2.6 Logarithmic, scaled Eddington flux (in units of erg cm− s− Hz− ) as a function of wavelength/energy 31 2.7 Logarithmic Eddington fluxes as a function of wavelength for supergiant models . 33 2.8 Ionization fractions of important ions at v(r) = 0.5 v , as a function of Teff, for models with typical X-ray emission ∞ 2.9 Helium ionization fractions as a function of local velocity . 37 2.10 Helium ionization fractions as a function of τRoss, for S30 models calculated by FASTWIND and WM-basic 2.11 Synthetic He ii 1640 and He ii 4686 profiles for our S30 model . 40 2.12 Ionization fractions of selected ions as a function of Teff, for 14 O-star models . 42 2.13 Radial stratification of phosphorus ionization fractions, as a function of τRoss ..... 43 2.14 Ionization fractions of P iv and P v as a function of normalized velocity for an S35 and S40 model 44 2.15 Ionization fractions of ions most affected by Auger ionization, at different depth points 45 2.16 Radial stratification of oxygen ionization fractions, as a function of τRoss, for an S40 model 48 2.17 Ionization fractions of oxygen, as a function of τRoss, for a D45 model . 49 2.18 Contour plots illustrating the radial dependence of the mass absorption coefficient, κν(r), as a function of wav 2.19 Radial variation of the mass absorption coefficient in dwarf and superginat models for specific values of wavelength 2.20 Density-weighted mean of the mass absorption coefficient,κ ¯ν, for the interval between 1.2 and 110 R , as a function ∗ 2.21 Ionization fractions of C iv (at v(r) = 0.5v ), as a function of Teff, and for different X-ray emission parameters ∞ 2.22 As above (C iv at v(r) = 0.5v ), but now for dwarf and supergiant models, for all X-ray emission parameters ∞ 2.23 As Fig. 2.21, but for N v at v(r) = 0.6v ........................ 63 ∞ 2.24 As Fig. 2.22, but for N v (v(r) = 0.6v )......................... 63 ∞ 2.25 As Fig. 2.21, but for O v at v(r) = 0.6v ......................... 64 ∞ 2.26 As Fig. 2.22, but for O v (v(r) = 0.6v ). ........................ 64 ∞ 2.27 As Fig. 2.21, but for O vi at v(r) = 0.6v ......................... 65 ∞ 2.28 As Fig. 2.22, but for O vi (v(r) = 0.6v )......................... 65 ∞ 2.29 As Fig. 2.21, but for P v at v(r) = 0.5v ......................... 66 ∞ 2.30 As Fig. 2.22, but for P v (v(r) = 0.5v ). ........................ 66 ∞ x LIST OF FIGURES 2.31 Ionization fractions of specific ions, as calculated by FASTWIND (black) and WM-basic (magenta) for dwarf 2.32 As Fig. 2.31, but for supergiant models. ..... 68 2.33 Emergent line profiles for strategic UV lines as calculated by WM-basic and FASTWIND 69 2.34 As Fig. 2.20, but for clumped models . 70 2.35 As Fig. 2.20, but averaged over the interval between 10 and 110 R .......... 70 ∗ 3.1 Ratios of ionization fractions resulting from our former and our new model atom, as a function of τRoss, for model 3.2 Bound-free cross-section of the C iii ground state including resonances and the resonance-free data 83 3.3 Ionization fractions of carbon ions, as a function of τRoss, for model D45 . 84 3.4 Impact of dielectronic recombination on C ii/iii lines, for the D35 model . 85 3.5 Ionization fraction of carbon ions, as a function of τRoss, for the S45 model, as calculated by WM-basic and F 3.6 C ii 5145, C iii 5696, and C iv 5801 line profiles for model D35 and similar models with relatively small changes 3.7 AsFig.3.6,butformodelS35 ............................ 89 3.8 Fine-tuning of stellar parameters (here, Teff), for the case of HD 36512 (O9.7V) . 92 3.9 Observed carbon spectrum of HD 36512 (O9.7V), and synthetic lines, calculated with carbon abundance of 8.25 3.10 As Fig. 3.9, but for HD 303311 (O6V), and a carbon abundance of 8.33 dex . 99 3.11 As Fig. 3.10, but for HD 93128 (O3.5V), and a carbon abundance of 8.23 dex . 99 3.12 As Fig. 3.9, but for HD 188209 (O9.5Iab), and a carbon abundance of 8.23 dex . 100 3.13 As Fig. 3.10, but for HD 169582 (O6Ia), and carbon abundance of 8.53 dex . 101 3.14 As Fig. 3.10, but for CygOB2-7 (O3I), and a carbon abundance of 8.03 dex .