Global asteroseismology of 19,000 red giants in the TESS Continuous Viewing Zones

Abstract

TESS (Transiting Exoplanet Survey Satellite) has produced long-term photometry for millions of stars across the sky. In this work, we present an asteroseismic catalogue of 19,151 red giants in the TESS Continuous Viewing Zones using sectors 1--87 (Years 1--7). We visually assessed the power spectra for oscillations, and then applied the computationally efficient nuSYD method to confirm reliability. We identified an increase of 80% in the number of previously known oscillating red giants at a TESS magnitude $>$ 8. We determined the frequency of maximum power ($\rm ν_{max}$) and the large frequency separation ($\rm Δν$) using the pySYD pipeline, achieving typical precisions of 1.5% and 1%, respectively. We classified the stars into Red Giant Branch (RGB) and Core Helium Burning (CHeB) classes using a Convolutional Neural Network. Using spectroscopic data for 10,298 stars with reliable asteroseismic measurements, we have been able to measure stellar mass and radii with precisions of 7.5% and 2.8%, which is comparable to that from 4-yr $Kepler$ data. A comparison of the seismic radii with Gaia radii shows excellent agreement. With three years of TESS data, the asteroseismic parameters are precise enough to identify the RGB bump and delineate the Zero Age Helium Burning edge. Combined with astrometric data, these parameters reveal established trends across the Galactic plane, providing a valuable set of uniformly determined asteroseismic parameters for Galactic Archaeology.

Figures (14)

• Figure 1: Colour-magnitude diagram using Gaia apparent magnitudes of all stars in TESS CVZ with TESS magnitude brighter than 13.5. The rectangle shows the 72,647 stars selected for analysis in this work.
• Figure 2: Solar like oscillations of a typical red giant. Panel a shows the power density spectra of an oscillating Kepler red giant (KIC 9075872, $K_{p}$ = 11.89 ) and Panel b for an oscillating red giant (TIC 237197414, $\rm T_{\rm mag}$ = 7.084) in the northern TESS CVZ.
• Figure 3: Gaia Absolute Magnitude ($M_{G}$) vs Frequency of Maximum power ($\nu_{\rm max}$) for all 16,094 Kepler stars in yu18. The red line corresponds to the fit provided in eqn. \ref{['eqn1']}.
• Figure 4: Frequency of Maximum power vs TESS Magnitude for all 17,617 stars in the sample. Top panel shows the stars colour coded by their detection probability. The bottom panel shows stars which were visually verified (black). The red points are the detections and the dashed line shows the empirical detection limit from honqlp.
• Figure 5: The correlation between $\nu_{\rm max}$ and $\Delta\nu$ for all 10,298 stars with reliable $\Delta\nu$ measurements is presented in Panel a. The dashed line represents a power-law fit in linear space. Panel b provides the same data, with the y-axis serving as a proxy for mass. Blue points indicate 7469 Red Giant Branch (RGB) stars, orange points denote 2723 Core Helium Burning (CHeB) stars, and grey points represent stars classified as ambiguous.