https://lib.uliege.be https://matheo.uliege.be Constraining the dynamics and masses of the TRAPPIST-1 planets with the transit timing variations method Auteur : Houge, Adrien Promoteur(s) : Gillon, Michaël Faculté : Faculté des Sciences Diplôme : Master en sciences spatiales, à finalité approfondie Année académique : 2019-2020 URI/URL : http://hdl.handle.net/2268.2/9196 Avertissement à l'attention des usagers : Tous les documents placés en accès ouvert sur le site le site MatheO sont protégés par le droit d'auteur. Conformément aux principes énoncés par la "Budapest Open Access Initiative"(BOAI, 2002), l'utilisateur du site peut lire, télécharger, copier, transmettre, imprimer, chercher ou faire un lien vers le texte intégral de ces documents, les disséquer pour les indexer, s'en servir de données pour un logiciel, ou s'en servir à toute autre fin légale (ou prévue par la réglementation relative au droit d'auteur). 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University of Li`ege Faculty of sciences Astrophysics, Geophysics and Oceanography department Constraining the dynamics and masses of the TRAPPIST-1 planets with the transit timing variations method Thesis presented by Adrien HOUGE to obtain the Master's degree in Space Sciences Board of Examiners: Olivier Absil Supervisor: Laetitia Delrez Micha¨elGillon Fran Pozuelos Valerie Van Grootel June 2020 Contents 1 Theoretical introduction1 1.1 Exoplanetology.......................................1 1.2 Transit............................................3 1.2.1 Method.......................................3 1.2.2 A discovery tool..................................7 1.2.3 Further studies...................................8 1.3 Transit timing variations................................. 11 1.3.1 Method....................................... 11 1.3.2 Results....................................... 12 1.4 TRAPPIST-1........................................ 14 1.4.1 Discovery...................................... 14 1.4.2 Host star...................................... 16 1.4.3 Planets....................................... 17 2 Goal of this Master thesis 21 3 Data acquisition and analysis 22 3.1 Observation......................................... 22 3.1.1 SPECULOOS project............................... 22 3.1.2 Data acquisition.................................. 24 3.2 Data processing....................................... 27 3.2.1 SSO pipeline.................................... 27 3.2.2 SPECPHOT.................................... 28 3.3 Data analysis........................................ 30 3.3.1 The Markov Chain Monte Carlo method................... 30 3.3.2 Analysis of the dataset.............................. 32 4 Results 37 4.1 Individual analysis..................................... 37 4.1.1 Transit timings and variations......................... 37 4.1.2 Flares........................................ 45 4.1.3 Blended transits.................................. 48 4.2 Global analysis....................................... 51 5 Conclusions and future prospects 55 A Baseline functions and correction factors 57 B Individual analysis - Lightcurves 59 Bibliography 67 ii Acknowledgements First of all, I would like to sincerely thank my supervisor, Micha¨elGillon, who selected me for this amazing project. This Master thesis offered me the possibility to develop my skills in several domains and gave me the opportunity, thanks to a complete immersion in a research environment, to confirm the fact that a research-related career is what I want to do with my life. I thank Elsa Ducrot for all her precious advice notably concerning the use of the MCMC algorithm. Despite being focused on her PhD and the writing of her article, she always man- aged to find time for me. I am grateful for all the help provided by Lionel Garcia concerning the use of specphot, and Sandrine Sohy for the informatics-related issues. I acknowledge Eric Agol for useful discussions about the transit timing variations method, and the members of the Board of Examiners, Olivier Absil, Laetitia Delrez, Fran Pozuelos, and Valerie Van Grootel, for the time they will devote to this Master thesis. Then, I would like to use this section for a special thanks to Micha¨elDe Becker, who supported me during all the important steps of my academic experience, from my registration in the Mas- ter in Space Sciences to the PhD applications, passing by the organization of my Erasmus in Oulu, Finland. This international exchange was a major turning point in my academic and per- sonal life, and I am very grateful towards him and the University of Li`egefor making it possible. In addition, I would like to thank my family, Sabrina, Philippe, Am´eline,and Eliott, for all the support during these five years at the University of Li`ege,and all the future support during my PhD in Exeter, England. Finally, I thank all my friends who helped to take my mind off when I needed some breaks, notably during the months of lock-down. I think notably about Fran¸cois,Alexis, Arnaud, Thibault and Julien from the EMH, Laura, Cl´emence,Margot, Dima, Guillaume, and Jascal. But also all my amazing international friends met during the Erasmus in Oulu, Jakob, Lili, Felix, Mojo, Pedro, Maeva, Samuel, David, and Ella. Last but not least, a very special thanks to my partner and best Tirolintie flatmate, Angelica. Despite being at more than 3000km from me, it feels like we are always next to each other. iii CHAPTER 1 Theoretical introduction 1.1 Exoplanetology Since the dawn of Humanity, we have tried to catch the meaning of our role in the Universe. Most of the ancient cultures used metaphysical models to understand human nature and make logical sense of the planets, the stars, the Moon, the Sun and their respective motions. The geocentric model, mainly supported by Aristotle and Ptolemy in Ancient Greece, was the first in attempting to provide an explanation without relying on supernatural or divine beliefs. In this model, the Earth and humans are the center of everything, the stars occupy a distant fixed background, and the planets, the Sun and the Moon are in circular motions around the Earth. Even though the latter concept had been accepted for more than a thousand years in Europe, it did not survive the Copernican revolution and was replaced by the heliocentric model, thanks to the rise of Newtonian mechanics combined with rigorous observations. In consequence, the Sun was gradually considered as an individual star similar to any visible one when looking up at the sky. And as a result, the Earth lost its singularity and became one common planet lost in the many others potentially cohabiting in the Universe. Following this approach, the evolution of life had no reason to be limited to a single planet and could have emerged in any other worlds, provided conditions for life development are met. Exoplanetology is based upon this thought and is dedicated to the search and study of extrasolar planets. Its most ambitious objective is the detection of traces of life beyond the Solar System. On top of that, other precious information can be gathered from this field. For example, the discovery of Jupiter-sized planets orbiting close to their host stars, named hot Jupiters, enabled scientists to confirm the fundamental process of planetary migration, which is of major importance in the evolution of planetary systems, Solar System included (see Nice model [1]). However, the detection of exoplanets remained a daunting task until the end of the last century. Their luminosity depends on their size, temperature and albedo (i.e. their ability to reflect the light from their host stars) and even under the best circumstances, it is extremely faint compared to the brightness of their host stars. Moreover, the size of a planetary system is small as opposed to the distance between the Earth and this system, resulting in a low angular separation between an exoplanet and its host (smaller than a second of arc). This makes the direct observation of exoplanets extremely challenging, which explains why most of the objects known so far have been discovered through indirect methods. 1 2 1. Theoretical introduction It is Otto Struve who paved the way in 1952. In its article "Proposal for a project of high- precision stellar radial velocity work" he argued that, provided a significant improvement in precision, putative short-period giant exoplanets could be detected by radial velocity and eclipse techniques, used at that time to study eclipsing binaries. Forty-three years later, in 1995, Michel Mayor and Didier Queloz used the first of these two techniques to announce the first genuine detection of an exoplanet, the gas giant 51 Pegasi b [2]. For their work, they were awarded the Nobel Prize in Physics in 2019. In the years that followed, several methods were developed and even more exoplanets were detected (Fig.1.1). As each method is more practical and efficient for different