Fundamental properties and evolution of exoplanets and their host stars Author: Mazin R.Nasralla Faculty of Science and Engineering Department of Physics and Astronomy in the School of Natural Sciences A dissertation submitted to The University of Manchester for the degree of Master of Science by Research. 2020 BLANK PAGE 2 Fundamental properties and evolution of exoplanets and their host stars Contents List of Figures 8 List of Tables 12 Abstract 19 Declaration 20 Copyright Statement 21 Acknowledgements 23 The Author 24 List of Abbreviations and Symbols 26 1 Introduction and review 29 1.1 Motivation . 29 1.2 History of exoplanets . 30 1.2.1 Methods of detection . 34 1.3 Exoplanet populations . 35 1.3.1 Selection bias and the characterisation of populations . 36 1.3.2 Improvements in instrumental sensitivity . 38 1.3.3 Hot Jupiters . 39 1.3.4 The Kepler revolution . 41 Mazin Nasralla 3 CONTENTS 1.3.5 Delineation of super-Earths, mini-Neptunes and photo- evaporation . 42 1.4 Formation mechanisms . 45 1.4.1 Observations from the Solar System and beyond . 45 1.4.2 Accretionary models . 46 1.4.3 Evidence from exoplanet detections . 49 1.5 Star, planet and disc interaction . 49 1.5.1 The origin of hot Jupiters . 49 1.5.2 Dynamical evolution . 51 1.5.3 Viscous migration through a gas-rich disk . 51 1.5.4 In-situ formation . 54 1.5.5 Evidence from multiple planetary systems . 55 1.5.6 Evidence from the Solar System of a dynamic past . 57 1.5.7 Why would migration stop at 0.05 au? . 58 1.5.8 Stellar radiation pressure . 58 1.5.9 Stellar tides . 58 1.6 Stellar evolution models . 63 1.6.1 The Hertzsprung–Russell diagram . 63 1.6.2 Stellar evolution tracks . 64 1.6.3 Stellar lifetime and mass dependency . 65 1.6.4 The initial mass function . 65 1.6.5 Main-sequence and post-main-sequence cycles . 66 1.6.6 Stellar mass loss . 68 1.7 Characterisation of exoplanet host stars . 69 1.7.1 Stellar parameters . 69 1.7.2 Techniques to derive age . 69 1.7.3 Measuring distance, and stellar radii . 73 1.7.4 Measuring metallicity and effective temperature . 74 1.7.5 Techniques to derive mass . 77 4 Fundamental properties and evolution of exoplanets and their host stars CONTENTS 1.8 Summary . 79 2 Stellar Evolution Model 81 2.1 Introduction . 81 2.2 Aspects of the model . 82 2.2.1 Creation of a pre-main-sequence model . 83 2.2.2 Reaction rates . 83 2.2.3 Opacities and equation of state . 84 2.2.4 Rotation . 85 2.2.5 Initial mass, and evolution of composition . 85 2.2.6 Timestep control, termination and reporting . 87 2.2.7 Mesh resolution . 88 2.2.8 Mass loss . 88 2.2.9 Atmospheric mixing and convective overshooting . 89 2.3 Systematic uncertainty in isochrones . 90 2.4 A grid of main-sequence models . 90 2.5 Comparison of our model to well-studied stars . 91 3 Probabilistic stellar parameters 95 3.1 Introduction . 95 3.2 Prior probability of observing a model star . 96 3.3 Stellar observations . 98 3.4 Maximum likelihood estimates of exo-host properties . 100 3.5 Model forecasts compared to observation . 103 3.6 Exceptions . 109 4 Current orbital evolution 111 4.1 Introduction . 111 4.2 Assumptions regarding orbital evolution . 111 Mazin Nasralla 5 CONTENTS 4.3 Modelling orbital decay due to stellar tides . 112 4.3.1 Calculating da/dt . 113 4.4 Orbital decay results . 113 4.4.1 Comments . 115 5 Future orbital evolution 117 5.1 Introduction . 117 5.2 Post main-sequence evolution and orbital decay . 117 5.3 Calculating orbital evolution over time . 118 5.4 Orbital evolution results . 118 5.5 Overview of results . 130 6 Discussion 133 6.1 Probability model . 133 6.1.1 Defining the measurements of accuracy and precision . 133 6.1.2 Analysis of results . 135 6.1.3 Age determination in low-mass stars . 136 6.1.4 Model results for evolved stars . 139 6.1.5 Outliers in the survey, and error detection . 140 6.1.6 Scope and value of such surveys . 142 6.2 Tidal evolution study . 142 6.2.1 Current orbital decay . 142 6.2.2 Future orbital decay . 146 6.2.3 WASP-12 b . 147 6.3 Tidal migration, and stellar spin-rate . 149 6.3.1 Investigating correlations between stellar and planetary parameters and exo-host spin rates . 149 6.3.2 Implications for planet distribution around subgiants . 156 6.4 Suggestions for subsequent study . 158 6.4.1 Improvements to the tidal model . 158 6 Fundamental properties and evolution of exoplanets and their host stars CONTENTS 6.4.2 Investigating the three-day build-up, and the formation of HJ systems . 158 6.4.3 Extending the model to habitable planetary systems, and nearby systems subject to observational study . 159 6.4.4 Measuring the ages of HJ exo-hosts . 159 6.4.5 Probing the Galaxy for systematic change . 160 7 Conclusions 161 A MESA inlist file for the model 165 B Probability model and orbital evolution results 173 Bibliography 239 Word Count: 28,381 (see page 238 for details.) Mazin Nasralla 7 CONTENTS BLANK PAGE 8 Fundamental properties and evolution of exoplanets and their host stars List of Figures 1.1 The planar b Pictoris debris disc. 32 1.2 Exoplanet detections and milestones. 33 1.3 Confirmed planets by methodology. 36 1.4 Pipeline injection. 37 1.5 Exoplanet detections by mass and orbital separation. 39 1.6 Distance to star vs Kepler magnitude. 41 1.7 The radius gap between SE and MN. 43 1.8 A stellar mass dependency in the radius gap? . 44 1.9 A model of the solar nebula. 45 1.10 A slice through the Semarkona meteorite detailing chondrules set in a black dust matrix. The image is 3.35mm x 3.65 mm. 47 1.11 Condensation sequence of solids in the solar nebula. 50 1.12 Spin-orbit misalignments (l) vs Teff for HJs. 51 1.13 Type I migration. Torque from density currents acting on an embedded planet. 52 1.14 Type II migration. Jupiter mass planet opens a gap in the disc. 53 1.15 Mass and orbital period of HJs and CJs. 54 1.16 Multiple-planet architecture (NEA, 8th September 2019). 55 1.17 Resonance structure within multiple-planet systems. 56 1.18 The Neptunian desert illustrating a region of space where Nep- tunes and SN are very rare (NEA, 21st July 2019). 56 Mazin Nasralla 9 LIST OF FIGURES 1.19 Stellar Tides. A key for the parameters that follow. 59 1.20 The 3 days pile-up. The distribution of semi-major axis for HJs with Mp ¡ 0.3 MJup peaks at 0.05 au (NEA, 5th March 2020). 61 1.21 Differential orbital and stellar rotation rates and stellar tides. 62 1.22 Torques on a 1 MJup planet embedded in a proplyd around a Sun-like star. 62 1.23 Density coded HR diagram from the Hipparcos catalogue featur- ing stars < 300 pc distance. 63 1.24 MESA stellar evolution track (1 Md). 64 1.25 The temporal evolution of a 1.5 Md star towards the RGB. 67 1.26 Rotation rate in solar units from different clusters. 72 1.27 Stellar rotation rates decreasing and converging over time. 73 1.28 Radial velocity curve for 51 Pegasi. 77 1.29 Power spectrum for a KOI, an asteroseisomological target. 78 2.1 Sodium D absorption lines in the spectra of exo-host HD 209458. 87 3.1 Prior PDF of metallicity, based on s = 0.3 dex and m = ´1.82 dex. 97 3.2 Prior PDFs for a Centauri A. 99 3.3 Galactic, stellar, and model forecast for a Centauri A, based on data from Heiter et al. (2015). 99 3.4 Probability map of a Centauri A. 102 3.5 Stellar mass. Model forecasts compared to the literature. 103 3.6 Stellar age. Model forecasts compared to the literature. 104 3.7 Surface gravity. Model forecasts compared to the literature. 105 3.8 Model mass forecasts versus the literature. 106 3.9 Age forecasts versus the literature. 106 3.10 log g forecasts versus the literature. 107 3.11 Teff forecasts versus the literature. 107 3.12 L˚ forecasts versus the literature. 108 10 Fundamental properties and evolution of exoplanets and their host stars LIST OF FIGURES 3.13 log Z forecasts versus the literature. 108 5.1 Future stellar and orbital evolution of planets 1-6. 120 5.2 Future stellar and orbital evolution of planets 7-12. 121 5.3 Future stellar and orbital evolution of planets 13-18. 122 5.4 Future stellar and orbital evolution of planets 19-24. 123 5.5 Future stellar and orbital evolution of planets 25-30. 124 5.6 Future stellar and orbital evolution of planets 31-36. 125 5.7 Planetary engulfments. (Planet labels listed in Tables 5.2–5.4). 129 5.8 HATS-18 b accelerating from 9 cm yr´1 to 16 m yr ´1 at engulf- ment. 131 6.1 Uncertainty and deviation from the NEA’s ages, linked to stellar mass. 138 6.2 Planet deficit, at a ă 1 au around stars with M˚ > 1.5 Md. (Data sourced from NEA, 17/09/2019). 144 6.3 Engulfment of WASP-12 b forecast by our tidal model.