Eduardo Campos Gonçalves
FCUP / IA
Abstract
For a long time, spectroscopy has been used to analyze and characterize the nature of stars, from their composition to the amount of stellar activity. Spectroscopy has also been used for the detection of exoplanets through the radial velocity method as was the famous discovery of 51 Pegasi b back in 1995. Since then thousands of exoplanets have been discovered using a variety of methods. As more and more exoplanets are known, interest has shifted to characterizing these bodies and to obtain data from small terrestrial exoplanets. This poses a challenge as the signal they induce in the light we observe is very small and on similar order to stellar activity. In fact, stellar rotation and line of sight phenomena like convective blueshift, are known to affect the shape and strength of spectral lines across a star's surface. The former can be observed through the Rossiter–McLaughlin effect and the latter is shown for example by Cegla et al. (2018). Our current technology does not allow for the resolution of details in stellar surfaces, however in the last few years a "Doppler shadow" method that relies on planetary transits has been employed to probe the spectrum of a stellar surface partly obscured by a transiting planet.
Such method was employed by another work of Cegla et al. (2016) for HD 189733, also by Dravins et al. (2017) and Dravins et al. (2018) for both HD 209458 and HD 189733 respectively, and most recently by Cristo, E. et al. (2024) for HD 189733. Until now these observations have been conducted with the use of Cross Correlation functions (CCFs) due to this method requiring very high resolution spectra. In this dissertation not only do we attempt at recreating the results from Dravins et al. (2018), but with new high resolution data from the ESPRESSO spectrograph, we extend this analysis to individual lines, namely the sodium doublet lines and the H alpha line.
2024 October 16, 13:30
IA/U.Porto
Centro de Astrofísica da Universidade do Porto (Classroom)
Rua das Estrelas, 4150-762 Porto
