(Charla Invitada) Signatures of Rocky Planet Engulfment in HAT-P-4

SAFFE, CARLOS

San Francisco

Congreso; Science and Evolution of the Gemini Observatory - SEG2018; 2018

Gemini Observatory - AURA

The detection of a possible chemical signature of planet formation in the photosphere of a star is a challenge for the current observational techniques. It requires a careful selection of the targets, obtain spectra with the highest possible quality (S/N), and a detailed analysis using the so-called full differential technique. I will start this talk by reviewing the statistical trends of metallicity for stars with and without exoplanets, for both main-sequence and giant stars. We will compare the chemical solar pattern with similar stars of the solar neighborhood i.e. solar-twins and solar-analogs, showing that our Sun do present a lack of refractory elements. Then, I will focus on the study of binary stars with similar components, which allow to increase the precision in the derivation of stellar parameters and chemical abundances, by applying the differential technique. Finally, I will present the results for the remarkable binary system HAT-P-4, with observations acquired through Gemini + GRACES (Gemini Remote Access to CFHT ESPaDOnS Spectrograph) under a fast-turnaround (FT) observing mode. Notably, the exoplanet host star HAT-P-4 is ~0.1 dex more metal rich than its companion, its Lithium content is greater by ~0.3 dex, and is enhanced in refractory elements relative to volatile. We propose a scenario where at the time of planet formation, the star HAT-P-4 locked the inner refractory material in planetesimals and rocky planets, and formed the outer gas giant planet at a greater distance. The inner rocky material (at least 10 MEarth) where then accreted, resulting the notable chemical pattern that we observe today in this binary system.