Asteroseismology of High-Mass Stars: New Insights of Stellar Interiors With Space Telescopes

Abstract

Massive stars are important metal factories in the Universe. They have short and energetic lives, and many of them inevitably explode as a supernova and become a neutron star or black hole. In turn, the formation, evolution and explosive deaths of massive stars impact the surrounding interstellar medium and shape the evolution of their host galaxies. Yet the chemical and dynamical evolution of a massive star, including the chemical yield of the ultimate supernova and the remnant mass of the compact object, strongly depend on the interior physics of the progenitor star. We currently lack empirically calibrated prescriptions for various physical processes at work within massive stars, but this is now being remedied by asteroseismology. The study of stellar structure and evolution using stellar oscillations-asteroseismology-has undergone a revolution in the last two decades thanks to high-precision time series photometry from space telescopes. In particular, the long-term light curves provided by the MOST, CoRoT, BRITE, Kepler/K2, and TESS missions provided invaluable data sets in terms of photometric precision, duration and frequency resolution to successfully apply asteroseismology to massive stars and probe their interior physics. The observation and subsequent modeling of stellar pulsations in massive stars has revealed key missing ingredients in stellar structure and evolution models of these stars. Thus, asteroseismology has opened a new window into calibrating stellar physics within a highly degenerate part of the Hertzsprung-Russell diagram. In this review, I provide a historical overview of the progress made using ground-based and early space missions, and discuss more recent advances and breakthroughs in our understanding of massive star interiors by means of asteroseismology with modern space telescopes.

Characterization of the variability in the O+B eclipsing binary HD 165246

“…Characterization of the variability (or lack thereof) in these stars is providing the basis upon which predictions of physical mechanisms can be tested. In particular, stars that reveal coherent oscillation modes whose degree and azimuthal order can be identified, are suitable to be probeb via asteroseismology (Aerts 2021;Bowman 2020). So far, such detections and identifications are typically achieved in only about 10% of the observed OB-type stars, but this fraction is expected to increase thanks to TESS.…”

“…Massive stars exhibit a multitude of phenomena, including (in some cases extreme) wind-mass loss (e.g., Vink et al 2011;Sander et al 2019), rapid rotation (e.g., Maeder 2009;Ekström et al 2012;de Mink et al 2013;Abdul-Masih et al 2019), magnetic fields (e.g., Wade et al 2016;Buysschaert et al 2017), as well as pulsations (e.g., Aerts et al 2010;Handler 2013;Bowman 2020). Additionally, massive O-and B-stars are observed to have a high binary or multiplicity fraction (Kiminki & Kobulnicky 2012;Sana et al 2012Sana et al , 2013Sana et al , 2014Aldoretta et al 2015).…”

Asteroseismology of Close Binary Stars: Tides and Mass Transfer

“…The subsequent gravity waves cannot pass the critical layer and waves dissipate strongly. Observationally, single upper main-sequence stars tend to have a nearly uniform rotation profile in the radiative envelope, inferred from asteroseismology (Bowman, 2020;Aerts, 2021) 3 . The gmode pulsating γ Dor stars (spectral type A-F-) in close binaries with P orb ≤ 10 d show a convective-core-boundary rotation period that is similar to the orbital period, suggesting that the tidal synchronization has already reached the deep interior Li et al, 2020a;Saio, 2020).…”

“…When forming global normal modes, these gravity (g) modes can be observed in photometry or spectroscopcy and be used to study the stellar interiors. Thanks to the recent space telescopes, significant advances have been made in asteroseismology (Aerts et al, 2010;Bowman, 2020) including, e.g., the self-excited gmode pulsators such as the F or A type γ Dor stars (Van Reeth et al, 2016;Li et al, 2020b) and the Slowly Pulsating Bstars (SPB) (Pápics et al, 2017). In binary stars, tidal forcing from the companion star naturally falls into the low-frequency (inertial and gravity mode) regime 1 , with characteristic periods on the order of days.…”

Space Photometry with Brite-Constellation

“…TESS (Ricker et al [29] focuses on the stars brighter than those observed by Kepler and the K2 follow-up, and it covers a sky area 400 times larger than that monitored by Kepler. As an example of the relevance of TESS data for asteroseismology we refer, for example, to Cunha et al [30], Antoci et al [31], Bowman [32] and Burssens et al [33].…”