Faculté des Sciences
Faculté des Sciences

Observation and analysis of transits of TRAPPIST-1 systems

Thimmarayappa, Darshini ULiège
Promotor(s) : Gillon, Michaël ULiège
Date of defense : 6-Sep-2018 • Permalink :
Title : Observation and analysis of transits of TRAPPIST-1 systems
Author : Thimmarayappa, Darshini ULiège
Date of defense  : 6-Sep-2018
Advisor(s) : Gillon, Michaël ULiège
Committee's member(s) : Grodent, Denis ULiège
Jehin, Emmanuel ULiège
Absil, Olivier ULiège
Language : English
Number of pages : 98
Keywords : [en] TRAPPIST-1
[en] Exoplanetology
[en] Markov Chain Monte-Carlo (MCMC)
[en] Photometry
[en] Analysis
Discipline(s) : Physical, chemical, mathematical & earth Sciences > Physics
Physical, chemical, mathematical & earth Sciences > Space science, astronomy & astrophysics
Target public : Researchers
Professionals of domain
General public
Institution(s) : Université de Liège, Liège, Belgique
Degree: Master en sciences spatiales, à finalité approfondie
Faculty: Master thesis of the Faculté des Sciences


[en] My chosen topic for this thesis is the newly discovered TRAPPIST-1 planetary system with its seven planets revolving around the nearby ultracool dwarf star. The main need to focus on the TRAPPIST-1 system is to refine the masses of the seven planets, to constrain their composition and also their dynamics. In order to do that we use the measured transit timing variations (TTVs) to constrain their masses, orbits and hence refine the transit parameters through analysis. Measured TTVs are used to detect a change in the orbital period of each planet caused by gravitational pull of the planets in a resonant chain, this causes the planets to accelerate and decelerate along its orbit in a packed planetary system and therefore change the orbital period. We also reduce the photometric data obtained from the Liverpool telescope over the time span of 2017/05/31 to 2017/10/28. The photometric data obtained consists of 19 light curves and each of these light curves were analyzed individually and then a global analysis was performed on all the transits pertaining to a single planet. The individual and global analysis was performed with the most recent version of the adaptive Markov Chain Monte-Carlo (MCMC) code developed by M. Gillon. For the reduction of the data, we first performed differential photometry to measure the flux of our target star with respect to a standard star in the field of view and eventually from this we obtain the dip in the value of the measured flux of a star during a planetary transit. Individual analysis is performed for each light curve to obtain the astrophysical and instrumental effects observed at the photometric variation level and finally we perform global analysis for a set of light curves obtained for the same planet. Both individual and global analysis is done in a preliminary chain of 10,000 steps and a secondary chain of 100,000 steps. In the global analysis, we improve the accuracy of the system parameters, de-trended light curves along with photometric representations which are also included in the report.\\

The global analysis result for TRAPPIST-1b gave us a transit duration of 0.025 $\pm 0.00050$ days with its 1 − $\sigma$ limit of the posterior PDF, similarly we have a value of 0.029$\pm0.00076$ days for TRAPPIST-1c and a value of 0.0388$\pm0.00075$ days for TRAPPIST-1e. These values are in good agreement with the values obtained from the Spitzer analysis. These timings will be useful to constrain further the dynamics of the TRAPPIST-1 system and the masses and compositions of its planets. We also compare the results with the already reduced Spritzer results, to check the accuracy of the results obtained from the Liverpool telescope. Some of our results are presented in the paper "The 0.6-4.55μm broadband transmission spectra of TRAPPIST-1 planets" (Ducrot et al. 2018, under review).



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  • Thimmarayappa, Darshini ULiège Université de Liège > Master sc. spatiales, à fin.


Committee's member(s)

  • Grodent, Denis ULiège Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
    ORBi View his publications on ORBi
  • Jehin, Emmanuel ULiège Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa)
    ORBi View his publications on ORBi
  • Absil, Olivier ULiège Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > ISSPSILAB
    ORBi View his publications on ORBi
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