Low-frequency gravity waves in blue supergiants revealed by high-precision space photometry

Abstract

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.

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Fig. 1: K2 data of the β Cep star EPIC 202929357.
Fig. 2: K2 data of the blue supergiant star EPIC 240255386.
Fig. 3: Gaia colour-magnitude diagram of OB stars observed by the K2 and TESS space missions.
Fig. 4: Relationship between intrinsic stellar brightness and IGW morphology.
Fig. 5: Asteroseismic potential of hot massive post-main sequence stars.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

Code availability

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.

References

  1. 1.

    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).

    ADS  Article  Google Scholar 

  2. 2.

    Maeder, A. & Meynet, G. The evolution of rotating stars. Annu. Rev. Astron. Astrophys. 38, 143–190 (2000).

    ADS  Article  Google Scholar 

  3. 3.

    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).

    Article  Google Scholar 

  4. 4.

    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).

    ADS  Article  Google Scholar 

  5. 5.

    Aerts, C., Christensen-Dalsgaard, J. & Kurtz, D. W. Asteroseismology (Springer, 2010).

  6. 6.

    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).

    ADS  Article  Google Scholar 

  7. 7.

    Beck, P. G. et al. Fast core rotation in red-giant stars as revealed by gravity-dominated mixed modes. Nature 481, 55–57 (2012).

    ADS  Article  Google Scholar 

  8. 8.

    Mosser, B. et al. Spin down of the core rotation in red giants. Astron. Astrophys. 548, A10 (2012).

    Article  Google Scholar 

  9. 9.

    Aerts, C., Mathis, S. & Rogers, T. Angular momentum transport in stellar interiors. Annu. Rev. Astron. Astrophys. (in the press).

  10. 10.

    Howell, S. B. et al. The K2 mission: characterization and early results. Publ. Astron. Soc. Pac. 126, 398–408 (2014).

    ADS  Article  Google Scholar 

  11. 11.

    Ricker, G. R. et al. Transiting Exoplanet Survey Satellite (TESS). J. Astron. Telesc. Instrum. Syst. 1, 1–10 (2015).

    ADS  Google Scholar 

  12. 12.

    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).

    ADS  Article  Google Scholar 

  13. 13.

    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).

    ADS  Article  Google Scholar 

  14. 14.

    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).

    ADS  Article  Google Scholar 

  15. 15.

    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).

    Article  Google Scholar 

  16. 16.

    Simón-Díaz, S. et al. Low-frequency photospheric and wind variability in the early-B supergiant HD 2905. Astron. Astrophys. 612, A40 (2018).

    Article  Google Scholar 

  17. 17.

    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).

    ADS  Article  Google Scholar 

  18. 18.

    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).

    ADS  Google Scholar 

  19. 19.

    Foreman-Mackey, D., Hogg, D. W., Lang, D. & Goodman, J. emcee: the MCMC hammer. Publ. Astron. Soc. Pac. 125, 306–312 (2013).

    ADS  Article  Google Scholar 

  20. 20.

    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).

    Article  Google Scholar 

  21. 21.

    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).

    Article  Google Scholar 

  22. 22.

    Gaia Collaboration et al. Gaia Data Release 2. Summary of the contents and survey properties. Astron. Astrophys. 616, A1 (2018).

    Article  Google Scholar 

  23. 23.

    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).

    ADS  Article  Google Scholar 

  24. 24.

    Green, G. M. et al. Galactic reddening in 3D from stellar photometry—an improved map. Mon. Not. R. Astron. Soc. 478, 651–666 (2018).

    ADS  Article  Google Scholar 

  25. 25.

    McCall, M. L. On determining extinction from reddening. Astron. J. 128, 2144–2169 (2004).

    ADS  Article  Google Scholar 

  26. 26.

    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).

    ADS  Article  Google Scholar 

  27. 27.

    Rogers, T. M. On the differential rotation of massive main-sequence stars. Astrophys. J. Lett. 815, L30 (2015).

    ADS  Article  Google Scholar 

  28. 28.

    Edelmann, P. V. F. et al. Three-dimensional simulations of massive stars: I. wave generation and propagation. Astrophys. J. 876, 4 (2019).

    ADS  Article  Google Scholar 

  29. 29.

    Cantiello, M. et al. Sub-surface convection zones in hot massive stars and their observable consequences. Astron. Astrophys. 499, 279–290 (2009).

    ADS  Article  Google Scholar 

  30. 30.

    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).

    MathSciNet  Article  Google Scholar 

  31. 31.

    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).

    ADS  Article  Google Scholar 

  32. 32.

    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).

    ADS  Article  Google Scholar 

  33. 33.

    Fuller, J. Heartbeat stars, tidally excited oscillations and resonance locking. Mon. Not. R. Astron. Soc. 472, 1538–1564 (2017).

    ADS  Article  Google Scholar 

  34. 34.

    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).

    Article  Google Scholar 

  35. 35.

    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).

    Article  Google Scholar 

  36. 36.

    Paxton, B. et al. Modules for experiments in stellar astrophysics (MESA). Astrophys. J. Suppl. Ser. 192, 3–37 (2011).

    ADS  Article  Google Scholar 

  37. 37.

    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).

    ADS  Article  Google Scholar 

  38. 38.

    Herwig, F. The evolution of AGB stars with convective overshoot. Astron. Astrophys. 360, 952–968 (2000).

    ADS  Google Scholar 

  39. 39.

    Seaton, M. J. Opacity project data on CD for mean opacities and radiative accelerations. Mon. Not. R. Astron. Soc. 362, L1–L3 (2005).

    ADS  Article  Google Scholar 

  40. 40.

    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).

    Article  Google Scholar 

  41. 41.

    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).

  42. 42.

    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).

    ADS  Article  Google Scholar 

  43. 43.

    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).

    ADS  Article  Google Scholar 

Download references

Acknowledgements

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).

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Definition of the science case and submission of the K2/TESS guest observer/investigator proposals: C.A., E.M., P.D.C., B.B., M.G.P., A.T., D.M.B., C.J., T.M.R., P.V.F.E. and R.P.R. Processing and data reduction of K2/TESS photometry: D.M.B., S.B., B.B., B.J.S.P. and T.R.W. Frequency analysis, fitting and interpretation of the results: D.M.B., C.J., M.M., C.A. and A.T. Reduction, analysis and interpretation of Gaia photometry: D.M.B. and M.G.P. Analysis, interpretation and comparison of results to hydrodynamical simulations: T.M.R., P.V.F.E. and R.P.R. Co-ordination of future follow-up spectroscopy: D.M.B., S.S.-D., N.C. and S.B. All authors discussed and commented on the manuscript.

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Correspondence to Dominic M. Bowman.

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Supplementary information

Supplementary Information

Supplementary Data captions and Supplementary Figs. 1–170

Supplementary Data 1

Parameters of the 114 OB stars observed by the K2 space mission.

Supplementary Data 2

Parameters of 53 OB stars in the LMC observed by the TESS space mission.

Supplementary Data 3

Fit parameters of residual amplitude spectra of K2 OB stars.

Supplementary Data 4

Fit parameters of amplitude spectra of TESS LMC OB stars.

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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

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