Preface i
Scientific and organising committees ii
Sponsors iii
List of participants iv
I Physics of star-planet magnetic interactions1
1 Introduction 2
1.1 The hot exoplanets population......................... 2
1.2 Observational status of star-planetmagnetic interactions ........... 3
2 Magnetic interactions in compact exosystems:overview 4
2.1 Sub- vs Super-alfvénic interaction....................... 4
2.2 Different regimes of sub-alfvénic interactions ................. 6
3 Magnetic interactions in compact exosystems: the Alfvén wings 7
3.1 Pre-requisites on magneto-hydrodynamic waves ................ 7
3.2 The concept of Alfvén wings.......................... 9
3.3 Energetics of Alfvén wings . . . . . . . .. . . . . . . . . . . . . . . . . . . 12
3.4 Angular momentum transfer and the secular evolution of stellar systems . . . 15
4 Conclusions 17
Bibliography 17
II Stellar variability in radial velocity 22
1 Introduction 23
2 From the instruments to radial velocities 24
2.1 Instruments . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . 25
2.2 From spectra to radial velocities . . . . .. . . . . . . . . . . . . . . . . . . 25
2.3 Observational strategies . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 26
2.4 Complementary information: chromospheric emission . . . . . . . . . . . . 27
2.5 Effect of stellar variability on exoplanetstudies in radial velocity: impact and challenges . . . . . . . . . . . . . . . . . . . . 28
3 Stellar processes contributing to radial velocities 29
3.1 General overview . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . 29
3.2 Spot and plage contrasts . . . . . . . . .. . . . . . . . . . . . . . . . . . . 30
3.3 Oscillations . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 32
3.4 The granulation . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . 33
3.5 Supergranulation . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . 36
3.6 Convective blueshift inhibition in plage .. . . . . . . . . . . . . . . . . . . 37
YL Star-Planet Interactions – Evry Schatzman School 2019
3.7 Evershed flows . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . 38
3.8 Meridional circulation . . . . . . . . . .. . . . . . . . . . . . . . . . . . . 38
3.9 Flares . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 40
4 Approaches to the problem 40
4.1 Mitigating techniques . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . 40
4.2 Simulations . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . 43
4.2.1 Simulations with 1-2 spots . . . . . . .. . . . . . . . . . . . . . . . 43
4.2.2 Simulations with complex activity patterns . . . . . . . . . . . . . . 44
4.2.3 Simulations of the small or large scale dynamics . . . . . . . . . . . 50
4.3 Stellar observations: simultaneous campaigns . . . . . . . . . . . . . . . . . 50
4.4 Observations of the Sun as a star . . . . .. . . . . . . . . . . . . . . . . . . 50
5 Conclusion 51
Bibliography 52
III Stellar activity and transits 65
1 Introduction 66
2 Solar and stellar activity observations 67
3 High precision photometry 68
3.1 Stellar rotation periods . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 69
3.2 Stellar surface reconstruction . . . . . .. . . . . . . . . . . . . . . . . . . . 71
3.3 Stellar differential rotation and star spot evolution . . . . . . . . . . . . . . . 72
4 Planetary transits and stellar activity features in photometry 73
4.1 Effect of non-occulted activity features on the transit depth . . . . . . . . . . 74
4.2 Effect of occulted activity features . . .. . . . . . . . . . . . . . . . . . . . 75
5 Starspots and faculae in transmission spectroscopy 77
6 Effects on other transit parameters 80
7 Planetary transits and stellar granulation 84
7.1 Effect on measured stellar parameters . . .. . . . . . . . . . . . . . . . . . 84
7.2 Effect on transit parameters . . . . . . .. . . . . . . . . . . . . . . . . . . . 84
8 Conclusions 86
Bibliography 87
IV High resolution spectroscopy for exoplanet characterisation 103
1 Introductory concepts 104
1.1 The underlying scientific questions . . . .. . . . . . . . . . . . . . . . . . . 104
1.2 Resolution vs Resolving Power . . . . . . .. . . . . . . . . . . . . . . . . . 106
1.3 Using spectroscopy to find exoplanets . . .. . . . . . . . . . . . . . . . . . 107
1.4 Exoplanets and their orbits . . . . . . . .. . . . . . . . . . . . . . . . . . . 108
1.5 Spectroscopy of transiting exoplanets . . .. . . . . . . . . . . . . . . . . . 109
1.5.1 Transmission spectroscopy . . . . . . . .. . . . . . . . . . . . . . . 109
1.5.2 Information from secondary eclipses: reflected light . . . . . . . . . 112
1.5.3 Information from secondary eclipses: thermal emission . . . . . . . . 113
1.5.4 Information from the whole orbit: phase curves . . . . . . . . . . . . 114
2 High-resolution spectroscopy of exoplanets115
2.1 Key characteristics . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . 115
2.2 The signal-to-noise formula and cross correlation . . . . . . . . . . . . . . . 116
2.3 Understanding the analysis of high-resolution exoplanet spectra . . . . . . . 118
2.4 Molecular and atomic species detected . . .. . . . . . . . . . . . . . . . . . 122
2.5 Thermal inversion layers . . . . . . . . .. . . . . . . . . . . . . . . . . . . 123
2.6 From demonstration to comparative exoplanetology . . . . . . . . . . . . . . 124
2.7 Follow-up of TESS exoplanets . . . . . . .. . . . . . . . . . . . . . . . . . 126
2.8 Cloudy atmospheres at high spectral resolution . . . . . . . . . . . . . . . . 127
3 The star as a source of astrophysical noise129
3.1 Stellar spectra are non-stationary . . . .. . . . . . . . . . . . . . . . . . . . 130
3.2 Stellar cross-correlation noise in day-side observations of exoplanets . . . . . 131
3.3 Stellar spectra are distorted during transit . . . . . . . . . . . . . . . . . . . 131
3.4 Modelling the background stellar spectrum .. . . . . . . . . . . . . . . . . 133
3.5 Stellar modelling to accurately measure exoplanet winds and rotation . . . . 135
4 Estimating significance and error bars 137
4.1 The signal-to-noise approach . . . . . . .. . . . . . . . . . . . . . . . . . . 137
4.2 The Welch t-test . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 138
4.3 Estimating the “model” cross correlation function . . . . . . . . . . . . . . . 139
4.4 Bayesian analysis on high-resolution spectra . . . . . . . . . . . . . . . . . . 140
4.4.1 Combining low- and high-resolution spectroscopy . . . . . . . . . . 141
5 Bridging the gap towards habitable planets141
5.1 Planets around M-dwarf stars . . . . . . .. . . . . . . . . . . . . . . . . . . 141
5.1.1 Detecting oxygen in planets around M-dwarfs . . . . . . . . . . . . . 143
5.1.2 Challenges in M-dwarf observations . . .. . . . . . . . . . . . . . . 143
5.2 Combining spectral and spatial resolution .. . . . . . . . . . . . . . . . . . 144
Bibliography 145
V Stellar Winds and Planetary Atmospheres 154
1 Introduction 155
2 Stellar rotation and activity evolution 158
2.1 The observational picture . . . . . . . . .. . . . . . . . . . . . . . . . . . . 158
2.2 The epochs of rotational evolution . . . .. . . . . . . . . . . . . . . . . . . 160
2.3 Activity and rotation . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . 161
2.4 Activity evolution . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 163
3 Properties and Evolution of Stellar Winds 164
3.1 Observational constraints on winds . . . .. . . . . . . . . . . . . . . . . . . 164
3.1.1 Rotational evolution . . . . . . . . . .. . . . . . . . . . . . . . . . 164
3.1.2 Radio observations . . . . . . . . . . .. . . . . . . . . . . . . . . . 166
3.1.3 Interactions with the interstellar medium. . . . . . . . . . . . . . . 166
3.1.4 Effects on planetary companions . . . . .. . . . . . . . . . . . . . . 168
3.2 Solar wind: basic properties . . . . . . .. . . . . . . . . . . . . . . . . . . 168
3.3 Wind physics . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . 171
3.4 Winds of active stars . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . 172
3.5 Coronal mass ejections . . . . . . . . . .. . . . . . . . . . . . . . . . . . . 174
4 Earth’s Upper Atmosphere and Wind Interactions 174
4.1 The vertical structure of the Earth’s atmosphere . . . . . . . . . . . . . . . . 175
4.2 Exospheres, magnetospheres, and winds . . .. . . . . . . . . . . . . . . . . 177
5 Planetary Upper Atmospheres and Escape 179
5.1 Hydrodynamic escape . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . 180
5.2 Upper atmospheres and active stars . . . .. . . . . . . . . . . . . . . . . . . 182
5.3 The importance of atmospheric cooling . . .. . . . . . . . . . . . . . . . . 184
5.4 The importance of the star’s rotational evolution . . . . . . . . . . . . . . . . 184
5.5 Stellar winds, CMEs, and habitable zone planets . . . . . . . . . . . . . . . . 186
6 Discussion 187
Bibliography 188
VI Main ways in which stars influence theclimate and surface hab[1]itability of theirplanets 202
1 Introduction 203
2 Influence of the bolometric emissiondistribution on the climate 205
3 Influence of the UV emission on the photochemistry 208
4 Influence of the X-EUV emission on atmospheric loss 209
5 Influence of the temporal evolution of the stellar emissions 210
6 Conclusions 211
Bibliography 212
