Almost all massive stars explode as supernovae and form a black hole or neutron star. The remnant mass and the impact of the chemical yield on subsequent star formation and galactic evolution strongly depend on the internal physics of the progenitor star, which is currently not well understood. The theoretical uncertainties of stellar interiors accumulate with stellar age, which is particularly pertinent for the blue supergiant phase. Stellar oscillations represent a unique method of probing stellar interiors, yet inference for blue supergiants is hampered by a dearth of observed pulsation modes. Here we report the detection of diverse variability in blue supergiants using the K2 and TESS space missions. The discovery of pulsation modes or an entire spectrum of low-frequency gravity waves in these stars allow us to map the evolution of hot massive stars towards the ends of their lives. Future asteroseismic modelling will provide constraints on ages, core masses, interior mixing, rotation and angular momentum transport. The discovery of variability in blue supergiants is a step towards a data-driven empirical calibration of theoretical evolution models for the most massive stars in the Universe.
This is a preview of subscription content
Subscribe to Nature+
Get immediate online access to the entire Nature family of 50+ journals
Subscribe to Journal
Get full journal access for 1 year
only $8.25 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Tax calculation will be finalised during checkout.
Get time limited or full article access on ReadCube.
All prices are NET prices.
The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.
The K2 systematics correction code k2sc is freely available and documented at https://github.com/OxES/k2sc. The iterative pre-whitening code is freely available and documented at https://github.com/IvS-KULeuven/IvSPythonRepository. The Python Markov chain Monte Carlo code emcee is freely available and documented at http://dfm.io/emcee/current/. The stellar evolution code, MESA, is freely available and documented at http://mesa.sourceforge.net/, and the stellar pulsation code, GYRE, is freely available and documented at https://bitbucket.org/rhdtownsend/gyre/wiki/Home.
Heger, A., Langer, N. & Woosley, S. E. Presupernova evolution of rotating massive stars. I. Numerical method and evolution of the internal stellar structure. Astrophys. J. 528, 368–396 (2000).
Maeder, A. & Meynet, G. The evolution of rotating stars. Annu. Rev. Astron. Astrophys. 38, 143–190 (2000).
Georgy, C. et al. Grids of stellar models with rotation. III. Models from 0.8 to 120 M ⊙ at a metallicity Z = 0.002. Astron. Astrophys. 558, A103 (2013).
Nomoto, K., Tominaga, N., Umeda, H., Kobayashi, C. & Maeda, K. Nucleosynthesis yields of core-collapse supernovae and hypernovae, and galactic chemical evolution. Nucl. Phys. A 777, 424–458 (2006).
Aerts, C., Christensen-Dalsgaard, J. & Kurtz, D. W. Asteroseismology (Springer, 2010).
Bedding, T. R. et al. Gravity modes as a way to distinguish between hydrogen- and helium-burning red giant stars. Nature 471, 608–611 (2011).
Beck, P. G. et al. Fast core rotation in red-giant stars as revealed by gravity-dominated mixed modes. Nature 481, 55–57 (2012).
Mosser, B. et al. Spin down of the core rotation in red giants. Astron. Astrophys. 548, A10 (2012).
Aerts, C., Mathis, S. & Rogers, T. Angular momentum transport in stellar interiors. Annu. Rev. Astron. Astrophys. (in the press).
Howell, S. B. et al. The K2 mission: characterization and early results. Publ. Astron. Soc. Pac. 126, 398–408 (2014).
Ricker, G. R. et al. Transiting Exoplanet Survey Satellite (TESS). J. Astron. Telesc. Instrum. Syst. 1, 1–10 (2015).
Saio, H. et al. MOST detects g- and p-modes in the B supergiant HD 163899 (B2 Ib/II). Astrophys. J. 650, 1111–1118 (2006).
Salmon, S. et al. Testing the effects of opacity and the chemical mixture on the excitation of pulsations in B stars of the Magellanic Clouds. Mon. Not. R. Astron. Soc. 422, 3460–3474 (2012).
Aerts, C., Puls, J., Godart, M. & Dupret, M.-A. Collective pulsational velocity broadening due to gravity modes as a physical explanation for macroturbulence in hot massive stars. Astron. Astrophys. 508, 409–419 (2009).
Aerts, C. et al. Kepler sheds new and unprecedented light on the variability of a blue supergiant: gravity waves in the O9.5Iab star HD 188209. Astron. Astrophys. 602, A32 (2017).
Simón-Díaz, S. et al. Low-frequency photospheric and wind variability in the early-B supergiant HD 2905. Astron. Astrophys. 612, A40 (2018).
Buysschaert, B. et al. Kepler’s first view of O-star variability: K2 data of five O stars in campaign 0 as a proof of concept for O-star asteroseismology. Mon. Not. R. Astron. Soc. 453, 89–100 (2015).
Aigrain, S., Parviainen, H. & Pope, B. J. S. K2SC: flexible systematics correction and detrending of K2 light curves using Gaussian process regression. Mon. Not. R. Astron. Soc. 459, 2408–2419 (2016).
Foreman-Mackey, D., Hogg, D. W., Lang, D. & Goodman, J. emcee: the MCMC hammer. Publ. Astron. Soc. Pac. 125, 306–312 (2013).
Blomme, R. et al. Variability in the CoRoT photometry of three hot O-type stars. HD 46223, HD 46150, and HD 46966. Astron. Astrophys. 533, A4 (2011).
Bowman, D. M. et al. Photometric detection of internal gravity waves in upper main-sequence stars. I. Methodology and application to CoRoT targets. Astron. Astrophys. 621, A135 (2019).
Gaia Collaboration et al. Gaia Data Release 2. Summary of the contents and survey properties. Astron. Astrophys. 616, A1 (2018).
Bailer-Jones, C. A. L., Rybizki, J., Fouesneau, M., Mantelet, G. & Andrae, R. Estimating distance from parallaxes. IV. Distances to 1.33 billion stars in Gaia Data Release 2. Astron. J. 156, 58–68 (2018).
Green, G. M. et al. Galactic reddening in 3D from stellar photometry—an improved map. Mon. Not. R. Astron. Soc. 478, 651–666 (2018).
McCall, M. L. On determining extinction from reddening. Astron. J. 128, 2144–2169 (2004).
Rogers, T. M., Lin, D. N. C., McElwaine, J. N. & Lau, H. H. B. Internal gravity waves in massive stars: angular momentum transport. Astrophys. J. 772, 21–39 (2013).
Rogers, T. M. On the differential rotation of massive main-sequence stars. Astrophys. J. Lett. 815, L30 (2015).
Edelmann, P. V. F. et al. Three-dimensional simulations of massive stars: I. wave generation and propagation. Astrophys. J. 876, 4 (2019).
Cantiello, M. et al. Sub-surface convection zones in hot massive stars and their observable consequences. Astron. Astrophys. 499, 279–290 (2009).
Couston, L.-A., Lecoanet, D., Favier, B. & Le Bars, M. The energy flux spectrum of internal waves generated by turbulent convection. J. Fluid Mech. 854, R3 (2018).
Aerts, C. et al. Forward asteroseismic modeling of stars with a convective core from gravity-mode oscillations: parameter estimation and stellar model selection. Astrophys. J. Suppl. Ser. 237, 15–45 (2018).
Szewczuk, W. & Daszyńska-Daszkiewicz, J. Domains of pulsational instability of low-frequency modes in rotating upper main sequence stars. Mon. Not. R. Astron. Soc. 469, 13–46 (2017).
Fuller, J. Heartbeat stars, tidally excited oscillations and resonance locking. Mon. Not. R. Astron. Soc. 472, 1538–1564 (2017).
Van Reeth, T., Tkachenko, A. & Aerts, C. Interior rotation of a sample of γ Doradus stars from ensemble modelling of their gravity-mode period spacings. Astron. Astrophys. 593, A120 (2016).
Pápics, P. I. et al. Signatures of internal rotation discovered in the Kepler data of five slowly pulsating B stars. Astron. Astrophys. 598, A74 (2017).
Paxton, B. et al. Modules for experiments in stellar astrophysics (MESA). Astrophys. J. Suppl. Ser. 192, 3–37 (2011).
Paxton, B. et al. Modules for experiments in stellar astrophysics (MESA): convective boundaries, element diffusion, and massive star explosions. Astrophys. J. Suppl. Ser. 234, 34–83 (2018).
Herwig, F. The evolution of AGB stars with convective overshoot. Astron. Astrophys. 360, 952–968 (2000).
Seaton, M. J. Opacity project data on CD for mean opacities and radiative accelerations. Mon. Not. R. Astron. Soc. 362, L1–L3 (2005).
Nieva, M.-F. & Przybilla, N. Present-day cosmic abundances. a comprehensive study of nearby early B-type stars and implications for stellar and Galactic evolution and interstellar dust models. Astron. Astrophys. 539, A143 (2012).
Przybilla, N., Nieva, M. F., Irrgang, A. & Butler, K. in New Advances in Stellar Physics: From Microscopic to Macroscopic Processes EAS Publications Series Vol. 63 (eds Alecian, G., Lebreton, Y., Richard, O. & Vauclair, G.) 13–23 (EDP Sciences, 2013).
Townsend, R. H. D. & Teitler, S. A. GYRE: an open-source stellar oscillation code based on a new magnus multiple shooting scheme. Mon. Not. R. Astron. Soc. 435, 3406–3418 (2013).
Townsend, R. H. D., Goldstein, J. & Zweibel, E. G. Angular momentum transport by heat-driven g-modes in slowly pulsating B stars. Mon. Not. R. Astron. Soc. 475, 879–893 (2018).
The K2 and TESS data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). Funding for the K2 mission is provided by NASA’s Science Mission Directorate. Funding for the TESS mission is provided by the NASA Explorer Program. STScI is operated by the Association of Universities for Research in Astronomy, under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX09AF08G and by other grants and contracts. The Gaia data in this paper come from the European Space Agency mission Gaia, processed by the Gaia Data Processing and Analysis Consortium (DPAC). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France; the SAO/NASA Astrophysics Data System; and the VizieR catalogue access tool, CDS, Strasbourg, France. The research leading to these results has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement number 670519: MAMSIE). T.M.R., P.V.F.E. and R.P.R. received support from STFC grant ST/L005549/1 and NASA grant NNX17AB92G. S.S.-D. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) through grants AYA2015-68012-C2-1 and Severo Ochoa SEV-2015-0548, and grant ProID2017010115 from the Gobierno de Canarias. B.J.S.P. is a NASA Sagan Fellow. This work was performed in part under contract with the Jet Propulsion Laboratory funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. T.R.W. acknowledges the support of the Australian Research Council (grant DP150100250).
The authors declare no competing interests.
Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary Data captions and Supplementary Figs. 1–170
Parameters of the 114 OB stars observed by the K2 space mission.
Parameters of 53 OB stars in the LMC observed by the TESS space mission.
Fit parameters of residual amplitude spectra of K2 OB stars.
Fit parameters of amplitude spectra of TESS LMC OB stars.
About this article
Cite this article
Bowman, D.M., Burssens, S., Pedersen, M.G. et al. Low-frequency gravity waves in blue supergiants revealed by high-precision space photometry. Nat Astron 3, 760–765 (2019). https://doi.org/10.1038/s41550-019-0768-1
The Astronomy and Astrophysics Review (2021)