D ISCOVERY ,C HARACTERIZATION , AND DISCOVERY,CHARACTERIZATION, D AND YNAMICS YNAMICS OF D OF TRANSITING EXOPLANETS T RANSITING INCENT AN YLEN E V V E XOPLANETS –V INCENT V AN E YLEN Discovery,Characterization, and Dynamics of Transiting Exoplanets Vincent Van Eylen PhDThesis,November 2015 Advisor:Prof.Simon Albrecht Co-advisors:Prof.Hans Kjeldsen,Prof.Josh Winn Stellar Astrophysics Centre (SAC) Department of Physics and Astronomy Faculty of Science and Technology Aarhus University,Denmark Vincent Van Eylen Discovery, Characterization, and Dynamics of Transiting Exoplanets November 2015 phd thesis advisors: Prof. Simon Albrecht Prof. Hans Kjeldsen Prof. Josh Winn Aarhus University – Faculty of Science and Technology Department of Physics and Astronomy – Stellar Astrophysics Centre (SAC) Ny Munkegade 120, Building 1520, Aarhus, Denmark front image: All known transiting exoplanets to date. The size of the circles is proportional to the size of the planets, while the colors range from orange for planets larger than Jupiter, to blue for planets smaller than Earth. The eight planets in the solar system are shown in white. PREFACE When doing astronomy for a few years, at some point you inevitably find yourself dragged down to tiny details - stuck at a computer, writing, calcu- lating, computing. It can be easy to forget about cool science. But there is a cure! Fly to Gran Canaria. Ignore all the tour operators and the families on their way to an all-inclusive hotel, instead, take the next plane to La Palma. Say hello to the beach. Drive up the Roque de los Muchachos: enjoy an hour cruising up on the windy road from sea level up to 2000 meter. Make sure that Radio Quarenta keeps you company. Get handed over keys, accompanied by the words, it’s your telescope now. Feel the building move as you point to a star. Be amazed as you realize the light you are now seeing has traveled hun- dreds of years to get here. Observe binary stars. Observe the effect of planets on stars. Split the light into a full spectrum of colors. Don’t be upset when a bit of your observing time gets taken away for a target of opportunity, instead realize that you are pointing your telescope elsewhere to look at a gamma ray burst. As you get more tired, blast several entire Muse concerts through the speakers and sing along – no one can hear you – and eat your super snacks. Go outside and realize that this is one of the darkest places in the world. No sound but the wind. Look up! See so many stars! See the milky way! Stay longer, and see even more as your eyes adapt! Wonder if all those stars have Earths? Identify the summer triangle – you don’t need to be in La Palma for this – where the Kepler field is and where we know of the existence of thousands of planets. Do they have forests and deserts and beautiful beaches? Bacteria or dinosaurs? Do you know? Realize that within our lifetime, we may find out. Wonder if there’s an exoplanet’s astronomer right now, who’s looking back at you? Look up once again, smile! Hurry back to the control room, worry that something may have gone wrong in your absence, but find that the tele- scope has been flawlessly compensating for the Earth’s rotation and tracking your star’s movement on the sky. Collect the last photons, they’ve traveled hundreds of years, so don’t be late! Close down the dome well into twilight. Enjoy the sunrise! This is the big picture – this is why I do astronomy. For the past three years, I’ve had the pleasure to learn about exoplanets in the uni- verse. Whether it was about the big picture or the tiny details, I have not done so alone. Thank you Simon, because I could not have wished for a better thesis ad- visor. I started as your first student, and if I am a scientist today it is in no small part due to your guidance. You’ve made me better in countless ways. I will take what you taught me with me through the rest of my career, in science or otherwise. Hans, tusind tak for the help and advice throughout the years, in the beginning of my degree, and even before. You taught me my first exoplanet course and supervised my masterthesis project. Without that, I wouldn’t be doing astronomy today, let alone studying exoplanets. I owe v a great deal of gratitude to Josh, for being a mentor and a source of scien- tific creativity and encouragement during six months at MIT. You went above and beyond what I could hope for. Thank you Sara, for hosting me in Boston during the early days of my PhD, and for being an example and a source of inspiration. There’s a countless number of researchers and collaborators who have my gratitude for teaching me, helping me, guiding me. Science can rarely be done alone, and I’ve had the pleasure to work with many brilliant people. Thank you Conny, my first astronomy mentor, without whom I would have never even made it to Denmark. Throughout the years in Aarhus I’ve met many wonderful people. Sandra, my first real friend in Denmark – now that my thesis is done you can expect me in Spain. Catalina, my fantastic flatmate, friend and so much more. Tina, for inspiring me to think outside the box and for making me take things less seriously. Gulnur, for always being there, and for countless conversations. Thank you Angela, for making me feel home away from home, and thank you to your beautiful dog Nevada – we’ve lived the snowiest Boston winter ever together. Lisa, my exoplanet friend on the other side of the ocean! None of what’s in this thesis would have ever materialized without so many colleagues at the Stellar Astrophysics Centre, and the morning coffee breaks. You and coffee are the best way to start the day and I am glad to call so many of you my friends. Mikkel, I’ve been grateful to rely on your scien- tific wisdom during so much of my PhD. Rikke: tak for kagen! Ditte, thank you for being so awesome. You, Tushar, Jakob, Chen, Michael, Rasmus, Bram, we’ve made the greatest office over the years. Jens and Fatemeh, for showing me the joys of La Palma, and so much more. What would work be without Fridays? Mikkel, Jens and Ditte, it’s been a pleasure to build a little office Fri- daybar, as well as a friendship which will outlast my time in Aarhus. Vichi, Karsten, Christoffer, Magnus, Victor, Brandon, Caro, I appreciate your regular contributions, be them talking or drinking. Mia, ever helpful with every little PhD struggle. Thank you Brigitte, for always compensating for my lack of administrative discipline, and for doing so with a smile. Louise, you’ve made many days just a little bit sunnier. Thank you, Jørgen, our center leader, and thanks to all the students in the exoplanet group! Thanks again to countless of the aforementioned people, for proofreading and improving this thesis in so many ways. Mum and dad, Wout, I enormously appreciate your encouragement regard- less of what it is I choose to undertake – I bet you didn’t expect I would ever become an astronomer. Sara, a friend in Belgium and beyond, for giving me a dinner to look forward to every few months. Michael, Christophe, Hanne, Christophe, Thomas, Pieter, Natascha, Sofie, Lynn, Kristien, Jorien, for mak- ing me remember what beer tastes like whenever I come home to Belgium and for being my friend as if I never left. Rhita: Parce que c’est toi le seul à qui j’peux dire, qu’avec toi je n’ai plus peur de vieillir! Vincent Van Eylen Aarhus, 1 November 2015 vi SUMMARY Are we alone in the Universe? So far, the question remains unanswered, but a significant leap forward was achieved two decades ago, with the discovery of the first planets orbiting stars other than our Sun. Almost 2000 exoplanets have now been detected. They are diverse in radius, mass and orbital period, but beyond those basic parameters very little is known about them. In this con- text, I have worked on the discovery and characterization of new, interesting planets, on the one hand, and on the other hand on studying the properties of known planets in much greater detail. To this end, in this thesis I make use of the transit method, which is based on the observed brightness drop of a star as a planet crosses in front of it. This thesis consists of two parts. The first part focuses on the discovery of new planets and the understanding of exoplanet properties. I report the discovery of the planet Kepler-410A b, a Neptune-sized planet in a 17 day orbit. Kepler-410 is composed of two stars, one of which hosts a transiting planet, and an additional non-transiting planet. The latter was discovered due to its gravitational influence on Kepler-410A b, which causes a variation in the timing of the transits. I was able to identify which of the two stars hosts the planet by using observations from the Kepler spacecraft, as well as infrared transit measurements using the Spitzer satellite. Furthermore, I found six new planets observed by Kepler, which were detected by precisely timing the duration of their transits to identify their host stars. I use asteroseismology, the study of stellar pulsations, to accurately measure the properties of the host stars and the planets.