Michael Palumbo
The Pennsylvania State University, US

Abstract
The radial velocity (RV) method, which measures the Doppler reflex motion of stars to infer planetary masses and orbital parameters, is also sensitive to intrinsic stellar variability, which can produce signals exceeding the 1 m/s level, dwarfing the ~10 cm/s RV amplitude produced by Earth-twin planets. To pave the way for future direct imaging missions, which aim to conduct targeted atmospheric characterizations of known Earth-mass planets, astronomers in the extremely precise radial velocity (EPRV) community will need to overcome this stellar activity barrier. In this presentation, I will discuss my work using two approaches for using observations of the Sun, the only star whose center-of-mass motion is precisely known, to understand the origin of and potential mitigation strategies for intrinsic stellar RV variability. In the first approach, I use high-resolution solar spectra to empirically model changes in absorption line shapes arising from convective motions in the solar atmosphere. Analyses of these synthetic stellar spectra suggest that future RV spectrographs will need to observe stars at higher spectral resolution in order to differentiate convection-induced line asymmetries from planet-induced Doppler shifts. In the second approach, I use observations from the space-based Solar Dynamics Observatory to understand how the spatial distributions of stellar surface inhomogeneities contribute to observed stellar variability. In closing, I will discuss how physical insights gleaned from these two approaches will enable RV measurements at greater accuracy using both current- and future-generation RV spectrographs.

2023 March 01, 13:30

IA/U.Porto
Centro de Astrofísica da Universidade do Porto (Auditorium)
Rua das Estrelas, 4150-762 Porto