We present an analysis of the first 20 second cadence light curves obtained by the TESS space telescope during its extended mission. We find improved precision 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 the depth of the convection zone. 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.

Since the onset of the “space revolution” of high-precision high-cadence photometry, asteroseismology has been demonstrated as a powerful tool for informing Galactic archeology investigations. The launch of the NASA Transiting Exoplanet Survey Satellite (TESS) mission has enabled seismic-based inferences to go full sky—providing a clear advantage for large ensemble studies of the different Milky Way components. Here we demonstrate its potential for investigating the Galaxy by carrying out the first asteroseismic ensemble study of red giant stars observed by TESS. We use a sample of 25 stars for which we measure their global asteroseimic observables and estimate their fundamental stellar properties, such as radius, mass, and age. Significant improvements are seen in the uncertainties of our estimates when combining seismic observables from TESS with astrometric measurements from the Gaia mission compared to when the seismology and astrometry are applied separately. Specifically, when combined we show that stellar radii can be determined to a precision of a few percent, masses to 5%–10%, and ages to the 20% level. This is comparable to the precision typically obtained using end-of-mission Kepler data.

Asteroseismology is a very useful tool for exploring the stellar interiors and evolutionary status and for determining stellar fundamental parameters, such as stellar mass, radius, surface gravity, and the stellar mean density. In this work, we use it to preliminarily analyse the 14 new type pulsating stars: Blue Large-Amplitude Pulsators (BLAPs) which is observed by Optical Gravitational Lensing Experiment project, to roughly analyse their evolutionary status. We adopt the theory of single star evolution and artificially set the mass-loss rate of |$\dot{M}=-2\times 10^{-4} {\rm M_{\odot }\,yr\mathrm{ ^{ -1}}}$| and mass-loss beginning at the radius of R = 40 |$\rm R_{\odot }$| on red giant branch to generate a series of theoretical models. Based on these theoretical models and the corresponding observations, we find that those BLAP stars are more likely to be the core helium burning stars. Most of them are in the middle and late phase of the helium burning.

Asteroseismology is a powerful tool for probing the inner structure and determining the evolutionary status and the fundamental parameters of stars. The oscillation spectra of slowly pulsating B (SPB) stars show almost uniform period spans, whose pattern is sensitive to the structure of the μ-gradient shell beyond the central convective core and hence can be used to efficiently describe their shapes and constrain the convective core. The SPB star KIC 8324482 was observed by Kepler for over 1470 days with a long-cadence pattern. Nearly equidistant period spacing patterns are found for the 14 connective dipolar modes that are extracted from the oscillation spectrum by Zhang et al. In the present work, we analyze them in depth with the χ ²-matching method and determine their χ ²-minimization models (CMMs). Based on those calculated CMMs, we find that KIC 8324482 is a young ( Myr), metal-poor ( dex), and intermediate-mass ( ) star with a convective core of in mass and in radius and with a surface rotation velocity . The central hydrogen abundance is of . Asteroseismic analyses indicate that the “propagation time” of g-mode in KIC 8324482 is of μHz. To well match with the observed period spacing pattern, an extra diffusion mixing ( ) should be considered, but the normal core overshooting f _ov must be fixed as zero in the best-fitting model. Such ultraweak mixing beyond the convective core corresponds to a fast rotation that is about 20–30 times the asteroseismic suggested rotation Ω_rot ≃ 0.2 μHz, if it is thought of as shear mixing induced completely by differential rotation.

The slowly pulsating B star HD 50230, which is in fact a hybrid B-type pulsator, has been observed by CoRoT for at least 137 days. Nearly equidistant period spacing patterns are found among eight modes that are extracted from the oscillation spectrum with more than 500 frequencies. However, it is thought to be most likely accidental by Szewczuk et al. In the present work, we analyze the eight modes in depth with the χ ²-matching method. Based on the best-fitting model (model MA), we find that they can be well explained as sequences of consecutive dipolar (l, m) = (1, 0). The period discrepancies between observations and the best-fitting model are within 100 s except for the outlier, which is up to 300 s. Based on the calculated χ ²-minimization models, we find that, for pure g-mode oscillations, the buoyancy radius, Λ₀, can be precisely measured with the χ ²-matching method between observations and calculations. It represents the “propagation time” of the g-mode from the stellar surface to the center. It is of Λ₀ = 245.78 ± 0.59 μHz with a precision of 0.24%. In addition, we also find that HD 50230 is a metal-rich (Z _init = 0.034–0.043) star with a mass of M = 6.15–6.27 M _⊙. It is still located in the hydrogen-burning phase with central hydrogen of X _C = 0.298–0.316 (or ); therefore, it has a convective core with a radius of R _cc = 0.525–0.536 R _⊙ (or ). In order to interpret the structure of the observed period spacing pattern well, the convective core overshooting (f _ov = 0.0175–0.0200) and the extra diffusion mixing ( ) should be taken into account in theoretical models.