Detection and characterization of planets orbiting oscillating red-giant stars with NASA’s TESS mission
Filipe Pereira (University of Porto)
The number of confirmed exoplanets orbiting evolved hosts is considerably small, compared to their dwarf counterparts. Of that already small sample, fewer still are known gas giants at close-in orbits. Nonetheless, finding and characterizing more of these systems provides a unique opportunity to not only test existing theories of giant planet formation and dynamical evolution, which does predict their low occurrence rate, but also to constrain other phenomena such as the radius inflation observed in “hot jupiters”.
To this end, I have worked to both improve the characterization of these systems and increase the sample of confirmed planets. To improve their characterization, I developed a tool to model both the transit signal and the stellar signals of the granulation and oscillations in the time domain simultaneously, using Gaussian Processes. The tool reduces the uncertainties in the recovered transit parameters, which, coupled with an asteroseismic characterization of the host star improves the precision of the determined planetary properties, and is also capable of determining properties of the stellar signals, such as granulation timescale and amplitude, as well as the frequency of maximum oscillation, with precision similar to analyses in the frequency domain. To increase the sample of confirmed planets, I am performing a search for planetary candidates in all bright (TESS mag < 10) low luminosity red-giant branch stars (LLRGBs) in the south sectors of the TESS mission. As of now, the sample of potential candidates found has been lower than expected by simulations, and might challenge estimates of the occurrence rate of these systems.