TESS Asteroseismology of the Known Red-giant Host Stars HD 212771 and HD 203949

The Transiting Exoplanet Survey Satellite (TESS) is performing a near all-sky survey for planets that transit bright stars. In addition, its excellent photometric precision enables asteroseismology of solar-type and red-giant stars, which exhibit convection-driven, solar-like oscillations. Simulations predict that TESS will detect solar-like oscillations in nearly 100 stars already known to host planets. In this paper, we present an asteroseismic analysis of the known red-giant host stars HD;212771 and HD;203949, both systems having a long-period planet detected through radial velocities. These are the first detections of oscillations in previously known exoplanet-host stars by TESS, further showcasing the mission?s potential to conduct asteroseismology of red-giant stars. We estimate the fundamental properties of both stars through a grid-based modeling approach that uses global asteroseismic parameters as input. We discuss the evolutionary state of HD;203949 in depth and note the large discrepancy between its asteroseismic mass (M-* = 1.23 0.15 MM* = 1.00 0.16 M if in the clump) and the mass quoted in the discovery paper (M-* = 2.1 0.1 M), implying a change >30% in the planet?s mass. Assuming HD;203949 to be in the clump, we investigate the planet?s past orbital evolution and discuss how it could have avoided engulfment at the tip of the red-giant branch. Finally, HD;212771 was observed by K2 during its Campaign 3, thus allowing for a preliminary comparison of the asteroseismic performances of TESS and K2. We estimate the ratio of the observed oscillation amplitudes for this star to be 更多