RVxTESS: Mitigating RV Signal Induced by Stellar Jitter

The Radial Velocity (RV) method, measuring the Doppler Shifts from stellar spectra, is widely used for the detection and characterization of exoplanets. For low-mass planets, RV detection typically requires cm/s precision, whereas the stellar jitter becomes an issue at the m/s level. Thus, it is essential to mitigate such stellar jitter in order to detect Earth-like planets using RVs.

Our project will focus on the asteroseismic signals of stellar jitter, including stellar oscillation and granulation. We study HD 5562 with fitting the model of stellar jitter to the observational data from TESS and Carnegie Planet Finder Spectrograph with Magellan II Telescope (Magellan/PFS). HD 5562 is a G-type subgiant with 0.93M_⨀. It has a magnitude of V=7.16 and a luminosity of 2.3L_⨀. Previously, mitigating the stellar oscillation signal is done by averaging it out via longer exposures and taking multiple observations. We take a different approach and conduct a Gaussian Process (GP) regression on the star's photometric and RV data to describe the stellar jitter.

Our new model suggests that the primary mode of its oscillation is around 15 minutes, shorter than the previous prediction of 44 minutes derived from its mass and luminosity. The periodogram suggests that photometrically, granulation has a stronger signal than oscillation in the light curve. The preliminary result for photometric data from TESS shows 2 granulation terms and 1 oscillation term. The RV fit will be aided by the GP regression of the light curve. Our project is part of the RVxTESS program (RVxTESS.com), which combines simultaneous TESS photometry with ground-based RV observations to study stellar jitter.