A 20-second cadence view of solar-type stars and their planets with TESS: asteroseismology of solar analogs and a re-characterization of π Men c

We present an analysis of the first 20-second cadence light curves obtained by the TESS space telescope during its extended mission. We find a precision improvement of 20-second data compared to 2-minute data for bright stars when binned to the same cadence (≈ 10-25% better for T ≲ 8 mag, reaching equal precision at T ≈ 13 mag), consistent with pre-flight expectations based on differences in cosmic ray mitigation algorithms. We present two results enabled by this improvement. First, we use 20-second data to detect oscillations in three solar analogs (γ Pav, ζ Tuc and π Men) and use asteroseismology to measure their radii, masses, densities and ages to ≈ 1%, ≈ 3%, ≈ 1% and ≈ 20% respectively, including systematic errors. Combining our asteroseismic ages with chromospheric activity measurements we find evidence that the spread in the activity-age relation is linked to stellar mass and thus convection-zone depth. Second, we combine 20-second data and published radial velocities to recharacterize π Men c, which is now the closest transiting exoplanet for which detailed asteroseismology of the host star is possible. We show that π Men c is located at the upper edge of the planet radius valley for its orbital period, confirming that it has likely retained a volatile atmosphere and that the “asteroseismic radius valley’ remains devoid of planets. Our analysis favors a low eccentricity for π Men c (< 0.1 at 68% confidence), suggesting efficient tidal dissipation (Q/k_2,1 ≲ 2400) if it formed via high-eccentricity migration. Combined, these early results demonstrate the strong potential of TESS 20-second cadence data for stellar astrophysics and exoplanet science.