Prospects for Galactic and stellar astrophysics with asteroseismology of giant stars in the TESS continuous viewing zones and beyond

Abstract

The NASA Transiting Exoplanet Survey Satellite (NASA-TESS) mission presents a treasure trove for understanding the stars it observes and the Milky Way, in which they reside. We present a first look at the prospects for Galactic and stellar astrophysics by performing initial asteroseismic analyses of bright (G < 11) red giant stars in the TESS southern continuous viewing zone (SCVZ). Using three independent pipelines, we detect νmax and Δν in 41 per cent of the 15 405 star parent sample (6388 stars), with consistency at a level of $\sim \! 2{{\ \rm per\ cent}}$ in νmax and $\sim \! 5{{\ \rm per\ cent}}$ in Δν. Based on this, we predict that seismology will be attainable for ∼3 × 105 giants across the whole sky and at least 104 giants with ≥1 yr of observations in the TESS-CVZs, subject to improvements in analysis and data reduction techniques. The best quality TESS-CVZ data, for 5574 stars where pipelines returned consistent results, provide high-quality power spectra across a number of stellar evolutionary states. This makes possible studies of, for example, the asymptotic giant branch bump. Furthermore, we demonstrate that mixed ℓ = 1 modes and rotational splitting are cleanly observed in the 1-yr data set. By combining TESS-CVZ data with TESS-HERMES, SkyMapper, APOGEE, and Gaia, we demonstrate its strong potential for Galactic archaeology studies, providing good age precision and accuracy that reproduces well the age of high [α/Fe] stars and relationships between mass and kinematics from previous studies based on e.g. Kepler. Better quality astrometry and simpler target selection than the Kepler sample makes this data ideal for studies of the local star formation history and evolution of the Galactic disc. These results provide a strong case for detailed spectroscopic follow-up in the CVZs to complement that which has been (or will be) collected by current surveys.

A 'Quick Look' at All-Sky Galactic Archeology with TESS: 158,000 Oscillating Red Giants from the MIT Quick-Look Pipeline

“…We consider our yield of 158,505 oscillating giants to be a lower bound estimate of the yield of oscillating giants across TESS's nominal mission because of the conservative measures we have used in both detection and vetting methods. In comparison to the predicted all-sky yield of ∼ 3×10 5 as reported by Mackereth et al (2021), our current yield suggests that there are still many giants that can potentially be detected from TESS. We defer more extensive detections across TESS FFIs to future work, which will better assess the sample completeness of red giants.…”

“…Similar precision levels were found by Stello et al (2021) when comparing seismic results from TESS data against those from 4-year Kepler data for ∼2,000 red giants observed by both Kepler and TESS. Furthermore, Mackereth et al (2021) recovered median mass uncertainties of ∼ 8% and age uncertainties of ∼ 26% for ∼1,700 red giants with G < 11 near the southern ecliptic pole, where FFI targets were observed by TESS for up to a year. Mackereth et al (2021) additionally indicate that the seismic ages of giants from TESS are sufficiently precise to distinguish chemicallyand kinematically-defined structures within the Milky Way disk.…”

“…Furthermore, Mackereth et al (2021) recovered median mass uncertainties of ∼ 8% and age uncertainties of ∼ 26% for ∼1,700 red giants with G < 11 near the southern ecliptic pole, where FFI targets were observed by TESS for up to a year. Mackereth et al (2021) additionally indicate that the seismic ages of giants from TESS are sufficiently precise to distinguish chemicallyand kinematically-defined structures within the Milky Way disk. Although the current outlook for red giant asteroseismology with TESS is promising, it has yet to be extended to the majority of TESS FFI targets.…”

“…Although the current outlook for red giant asteroseismology with TESS is promising, it has yet to be extended to the majority of TESS FFI targets. Not only is this because significantly more effort is required to sys-tematically detect populations of oscillating red giants across the millions of TESS FFI targets, but detailed seismic parameters like the large frequency separation are difficult to measure with one-month long observations (Hekker et al 2012;Mosser et al 2019;Mackereth et al 2021;Stello et al 2021). The frequency at maximum oscillation power, ν max , however, can be measured from any star with a detected oscillation power excess, making it a more accessible seismic measurement for inferring fundamental stellar properties.…”

Final Targeting Strategy for the SDSS-IV APOGEE-2S Survey

“…In addition to better understanding the Milky Way through classic Galactic astronomy exploration, as APOGEE-1 was originally designed to perform, the APOGEE dataset has also been used to study scientific fields outside of it's original intent, delving into stellar astrophysics (Pinsonneault et al 2014;Epstein et al 2014;Pinsonneault et al 2018;Mackereth et al 2021), studies of the ISM (Schultheis et al 2014;Zasowski et al 2015b,a), and even time series analyses of radial velocity variability as an indicator of stellar companions (Troup et al 2016;Badenes et al 2018;Clark Cunningham et al 2019;Price-Whelan et al 2020;Mazzola et al 2020), planet hosts (Fleming et al 2015;Cañas et al 2018;Wilson et al 2018;Cañas et al 2019a,b) and intrinsically variable stars (Chojnowski et al 2015(Chojnowski et al , 2019(Chojnowski et al , 2020Lewis et al 2020).…”