Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Outbursts of luminous blue variable stars from variations in the helium opacity

Abstract

Luminous blue variables are massive, evolved stars that exhibit large variations in luminosity and size on timescales from months to years, with high associated rates of mass loss1,2,3,4,5. In addition to this on-going variability, these stars exhibit outburst phases, during which their size increases and as a result their effective temperature decreases, typically to about 9,000 kelvin3,6. Outbursts are believed to be caused by the radiation force on the cooler, more opaque, outer layers of the star balancing or even exceeding the force of gravity, although the exact mechanisms are unknown and cannot be determined using one-dimensional, spherically symmetric models of stars because such models cannot determine the physical processes that occur in this regime7. Here we report three-dimensional simulations of massive, radiation-dominated stars, which show that helium opacity has an important role in triggering outbursts and setting the observed effective temperature during outbursts of about 9,000 kelvin. It probably also triggers the episodic mass loss at rates of 10−7 to 10−5 solar masses per year. The peak in helium opacity is evident in our three-dimensional simulations only because the density and temperature of the stellar envelope (the outer part of the star near the photosphere) need to be determined self-consistently with convection, which cannot be done in one-dimensional models that assume spherical symmetry. The simulations reproduce observations of long-timescale variability, and predict that convection causes irregular oscillations in the radii of the stars and variations in brightness of 10–30 per cent on a typical timescale of a few days. The amplitudes of these short-timescale variations are predicted to be even larger for cooler stars (in the outburst phase). This short-timescale variability should be observable with high-cadence observations.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Hertzsprung–Russell diagram for LBVs.
Fig. 2: Evolution of spherically averaged radial profiles for run T9L6.2.
Fig. 3: A snapshot of the three-dimensional density and radiation energy density from run T19L6.4.
Fig. 4: Evolution of the total luminosity measured from the outer boundary of the simulation box.

Similar content being viewed by others

Data availability

The simulation data are available from the corresponding author on request.

References

  1. Humphreys, R. M. & Davidson, K. The most luminous stars. Science 223, 243–249 (1984).

    Article  ADS  CAS  Google Scholar 

  2. Lamers, H. J. G. L. M. & Fitzpatrick, E. L. The relationship between the Eddington limit, the observed upper luminosity limit for massive stars, and the luminous blue variables. Astrophys. J. 324, 279–287 (1988).

    Article  ADS  CAS  Google Scholar 

  3. Humphreys, R. M. & Davidson, K. The luminous blue variables: astrophysical geysers. Publ. Astron. Soc. Pacif. 106, 1025–1051 (1994).

    Article  ADS  Google Scholar 

  4. Owocki, S. P. in Very Massive Stars in the Local Universe (ed. Vink, J. S.) 113–156 (Springer, Cham, 2015).

  5. Smith, N. Luminous blue variables and the fates of very massive stars. Phil. Trans. R. Soc. Lond. A 375, 20160268 (2017).

    Article  ADS  Google Scholar 

  6. Smith, N., Vink, J. S. & de Koter, A. The missing luminous blue variables and the bistability jump. Astrophys. J. 615, 475–484 (2004).

    Article  ADS  CAS  Google Scholar 

  7. Paxton, B. et al. Modules for experiments in stellar astrophysics (MESA): planets, oscillations, rotation, and massive stars. Astrophys. J. Suppl. Ser. 208, 4 (2013).

    Article  ADS  Google Scholar 

  8. Jiang, Y.-F., Stone, J. M. & Davis, S. W. An algorithm for radiation magnetohydrodynamics based on solving the time-dependent transfer equation. Astrophys. J. Suppl. Ser. 213, 7 (2014).

    Article  ADS  Google Scholar 

  9. Jiang, Y.-F., Cantiello, M., Bildsten, L., Quataert, E. & Blaes, O. Local radiation hydrodynamic simulations of massive star envelopes at the iron opacity peak. Astrophys. J. 813, 74 (2015).

    Article  ADS  Google Scholar 

  10. Jiang, Y.-F., Cantiello, M., Bildsten, L., Quataert, E. & Blaes, O. The effects of magnetic fields on the dynamics of radiation pressure-dominated massive star envelopes. Astrophys. J. 843, 68 (2017).

    Article  ADS  Google Scholar 

  11. Jiang, Y.-F., Stone, J. M. & Davis, S. W. A global three-dimensional radiation magneto-hydrodynamic simulation of super-eddington accretion disks. Astrophys. J. 796, 106 (2014).

    Article  ADS  Google Scholar 

  12. Groh, J. H. et al. On the nature of the prototype luminous blue variable Ag Carinae. I. Fundamental parameters during visual minimum phases and changes in the bolometric luminosity during the S-Dor cycle. Astrophys. J. 698, 1698–1720 (2009).

    Article  ADS  CAS  Google Scholar 

  13. Mehner, A. et al. Spectroscopic and photometric oscillatory envelope variability during the S Doradus outburst of the luminous blue variable R71. Astron. Astrophys. 608, A124 (2017).

    Article  Google Scholar 

  14. Conroy, C. et al. A complete census of luminous stellar variability on day to decade timescales. Astrophys. J. (in the press); preprint at https://arxiv.org/abs/1804.05860.

  15. Wolf, B., Stahl, O. & Inverse, P. Cygni-type profiles in the spectrum of the luminous blue variable S Doradus. Astron. Astrophys. 235, 340–344 (1990).

    ADS  CAS  Google Scholar 

  16. Smith, N. & Owocki, S. P. On the role of continuum-driven eruptions in the evolution of very massive stars and population III stars. Astrophys. J. 645, L45–L48 (2006).

    Article  ADS  CAS  Google Scholar 

  17. Vink, J. S., de Koter, A. & Lamers, H. J. G. L. M. Mass-loss predictions for O and B stars as a function of metallicity. Astron. Astrophys. 369, 574–588 (2001).

    Article  ADS  CAS  Google Scholar 

  18. Smith, N. Mass loss: its effect on the evolution and fate of high-mass stars. Annu. Rev. Astron. Astrophys. 52, 487–528 (2014).

    Article  ADS  CAS  Google Scholar 

  19. Lovekin, C. C. & Guzik, J. A. Pulsations as a driver for LBV variability. Mon. Not. R. Astron. Soc. 445, 1766–1773 (2014).

    Article  ADS  CAS  Google Scholar 

  20. Smith, N. & Tombleson, R. Luminous blue variables are antisocial: their isolation implies that they are kicked mass gainers in binary evolution. Mon. Not. R. Astron. Soc. 447, 598–617 (2015).

    Article  ADS  Google Scholar 

  21. Choi, J. et al. MESA isochrones and stellar tracks (MIST). I. Solar-scaled models. Astrophys. J. 823, 102 (2016).

    Article  ADS  Google Scholar 

  22. Brott, I. et al. Rotating massive main-sequence stars. I. Grids of evolutionary models and isochrones. Astron. Astrophys. 530, A115 (2011).

    Article  Google Scholar 

  23. Ekström, S. et al. Grids of stellar models with rotation. I. Models from 0.8 to 120 M ʘ at solar metallicity (Z=0.014). Astron. Astrophys. 537, A146 (2012).

    Article  Google Scholar 

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

    Article  ADS  Google Scholar 

  25. Paxton, B. et al. Modules for experiments in stellar astrophysics (MESA): binaries, pulsations, and explosions. Astrophys. J. Suppl. Ser. 220, 15 (2015).

    Article  ADS  Google Scholar 

  26. 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 (2018).

    Article  ADS  Google Scholar 

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

    Article  ADS  Google Scholar 

  28. Iglesias, C. A. & Rogers, F. J. Updated opal opacities. Astrophys. J. 464, 943–953 (1996).

    Article  ADS  CAS  Google Scholar 

  29. Jiang, Y.-F., Stone, J. & Davis, S. W. Super-Eddington accretion disks around supermassive black holes. Preprint at https://arxiv.org/abs/1709.02845 (2017).

Download references

Acknowledgements

We thank J. Insley (ALCF) for helping us to make the image shown in Fig. 3, N. Smith for providing the data for LBVs, and B. Paxton and J. Goodman for conversations and comments. This research was supported in part by the NASA ATP grant ATP-80NSSC18K0560, the National Science Foundation under grant number NSF PHY 11-25915, 17-48958, and in part by a Simons Investigator award from the Simons Foundation (to E.Q.) and the Gordon and Betty Moore Foundation through grant GBMF5076. An award of computer time was provided by the Innovative and Novel Computational Impact on Theory and Experiment (INCITE) programme. This research used resources of the Argonne Leadership Computing Facility and National Energy Research Scientific Computing Center, which are DOE Offices of Science User Facility supported under contract DE-AC02-06CH11357 and DE-AC02-05CH11231. Resources supporting this work were also provided by the NASA High-End Computing (HEC) programme through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center. The Flatiron Institute is supported by the Simons Foundation

Reviewer information

Nature thanks C. Lovekin and S. Owocki for their contribution to the peer review of this work.

Author information

Authors and Affiliations

Authors

Contributions

Y.-F.J. ran the simulations, analysed the results and wrote the first draft of the paper. M.C. ran the MESA one-dimensional stellar evolution calculations and made Fig. 1. M.C., L.B., E.Q., O.B. and J.S. read and commented on the manuscript.

Corresponding author

Correspondence to Yan-Fei Jiang.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Video 1

The video is in mp4 format and it is 32 seconds long. It shows the evolution of density for the simulation T19L6.4 described in the paper. The video starts from a spherically symmetric initial condition and ends with a fully turbulent envelope.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Jiang, YF., Cantiello, M., Bildsten, L. et al. Outbursts of luminous blue variable stars from variations in the helium opacity. Nature 561, 498–501 (2018). https://doi.org/10.1038/s41586-018-0525-0

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41586-018-0525-0

Keywords

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing