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Astrophysics

, Volume 61, Issue 2, pp 262–285 | Cite as

Light Chemical Elements in Stars: Mysteries and Unsolved Problems

  • L. S. Lyubimkov
REVIEW

The first eight elements of the periodic table are discussed: H, He, Li, Be, B, C, N, and O. They are referred to as key elements, given their important role in stellar evolution. It is noteworthy that all of them were initially synthesized in the Big Bang. The primordial abundances of these elements calculated using the Standard Model of the Big Bang (SMBB) are presented in this review. The good agreement between the SMBB and observations of the primordial abundances of the isotopes of hydrogen and helium, D, 3He, and 4He, is noted, but there is a difference of ~0.5 dex for lithium (the isotope 7Li) between the SMBB and observations of old stars in the galactic halo that has not yet been explained. The abundances of light elements in stellar atmospheres depends on the initial rotation velocity, so the typical rotation velocities of young Main Sequence (MS) stars are examined. Since the data on the abundances of light elements in stars are very extensive, the main emphasis in this review is on several unsolved problems. The helium abundance He/H in early B-type of the MS stars shows an increment with age; in particular, for the most massive B stars with masses M = 12−19M⦿, He/H increases by more than a factor of two toward the end of the MS. Theoretical models of stars with rotation cannot explain such a large increase in He/H. For early B- and late O-type MS stars that are components of close binary systems, He/H undergoes a sharp jump in the middle of the MS stage that is a mystery for the theory. The anomalous abundance of helium (and lithium) in the atmospheres of chemically peculiar stars (types He-s, He-w, HgMn, Ap, and Am) is explained in terms of the diffusion of atoms in surface layers of the stars, but this hypothesis cannot yet explain all the features of the chemical composition of these stars. The abundances of lithium, beryllium, and boron in FGK-dwarfs manifest a trend with decreasing effective temperature T eff as well as a dip at T eff ~ 6600 K in the Hyades and other old clusters. The two effects are among the unsolved problems. In the case of lithium, there is special interest in FGK-giants and supergiants that are rich in lithium (they have logε(Li)≥ 2). Most of them cannot be explained in terms of the standard theory of stellar evolution, so nonstandard hypotheses are invoked: the recent synthesis of lithium in a star and the engulfment by a star of a giant planet with mass equal to that of Jupiter or greater. An analysis of the abundances of carbon, nitrogen, and oxygen in early B- and late O-stars of the MS indicates that the C II, N II, and O II ions are overionized in their atmospheres. For early B-type MS stars, good agreement is found between observations of the N/O ratio and model calculations for rotating stars. A quantitative explanation of the well-known “nitrogen-oxygen” anticorrelation in FGK-giants and supergiants is found. It reflects the dependence of the anomalies in N and C on the initial rotation velocity V0. The stellar rotation models which yield successful explanations for C, N. and O cannot, however, explain the observed helium enrichment in early B-type MS stars.

Keywords

Stars chemical composition stellar rotation stellar evolution 

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References

  1. 1.
    M. Asplund, N. Grevesse, A. J. Sauval, et al., Ann. Rev. Astron. Astrophys. 47, 481 (2009).CrossRefADSGoogle Scholar
  2. 2.
    L. S. Lyubimkov, Kinematics and Physics of Celestial Bodies 26, 169 (2010).CrossRefADSGoogle Scholar
  3. 3.
    L. S. Lyubimkov, Astrophysics 59, 411 (2016).CrossRefADSGoogle Scholar
  4. 4.
    A. Coc, S. Goriely, Y. Xu, et al., Astrophys. J. 744, 158 (2012).CrossRefADSGoogle Scholar
  5. 5.
    R. J. Cooke, M. Pettini, R. A. Jorgenson, et al., Astrophys. J. 781, id. 31 (2014).Google Scholar
  6. 6.
    Y. I. Izotov, T. X. Thuan, and N. G. Guseva, Mon. Not. Roy. Astron. Soc. 445, 778 (2014).CrossRefADSGoogle Scholar
  7. 7.
    T. Bania, R. Rood, and D. Balser, Nature, 415, 54 (2002).CrossRefADSGoogle Scholar
  8. 8.
    M. Spite, F. Spite, and P. Bonifacio, Mem. Soc. Astron. Italiana Suppl. 22, 9 (2012).ADSGoogle Scholar
  9. 9.
    M. Spite, F. Spite, E. Caffau, et al., Astron. Astrophys. 582, A74 (2015).CrossRefADSGoogle Scholar
  10. 10.
    F. Spite and M. Spite, Astron. Astrophys. 115, 357 (1982).ADSGoogle Scholar
  11. 11.
    R. H. Cyburt, B. D. Fields, K. A. Olive, et al., Modern Physics, 88, id. 015004 (2016).Google Scholar
  12. 12.
    P. Bonifacio, L. Sbordone, E. Caffau, et al., Astron. Astrophys. 542, A87 (2012).CrossRefGoogle Scholar
  13. 13.
    A. Maeder, Physics, Formation and Evolution of Rotating Stars. Springer, Berlin (2009).Google Scholar
  14. 14.
    C. Georgy, S. Ekstrom, A. Granada, et al., Astron. Astrophys. 553, A24 (2013).CrossRefGoogle Scholar
  15. 15.
    C. W. Allen, Astrophysical Quantities (3 ed.), Athlone Press, London (1973).Google Scholar
  16. 16.
    H. A. Abt, H. Levato, and M. Grosso, Astrophys. J. 573, 359 (2002).CrossRefADSGoogle Scholar
  17. 17.
    S. Simón-Diaz and A. Herrero, Astron. Astrophys. 562, A135 (2014).CrossRefADSGoogle Scholar
  18. 18.
    G. A. Bragança, S. Daflon, K. Cunha, et al., Astron. J. 144, 130 (2012).CrossRefADSGoogle Scholar
  19. 19.
    J. Zorec and F. Royer, Astron. Astrophys. 537, A120 (2012).CrossRefADSGoogle Scholar
  20. 20.
    L. S. Lyubimkov, Pis’ma v Astron. zh. 1 (11), 29 (1975).ADSGoogle Scholar
  21. 21.
    L. S. Lyubimkov, Astrophysics 13, 71 (1977).CrossRefADSGoogle Scholar
  22. 22.
    L. S. Lyubimkov, S. I. Rostopchin, and D. L. Lambert, Mon. Not. Roy. Astron. Soc. 351, 745 (2004).CrossRefADSGoogle Scholar
  23. 23.
    L. S. Lyubimkov, Astrophys. Space Sci. 243, 329 (1996).CrossRefADSGoogle Scholar
  24. 24.
    E. Sturm and K. P. Simon, Astron. Astrophys. 282, 93 (1994).ADSGoogle Scholar
  25. 25.
    K. P. Simon, E. Sturm, and A. Fiedle, Astron. Astrophys. 292, 507 (1994).ADSGoogle Scholar
  26. 26.
    L. S. Lyubimkov, Chemical Composition of Stars: Method and Results of Analysis, Astroprint, Odessa (1995).Google Scholar
  27. 27.
    L. S. Lyubimkov, Bull. Crimean Astrophys. Obs. 110, 9 (2014).CrossRefADSGoogle Scholar
  28. 28.
    A. Heger and N. Langer, Astrophys. J. 544, 1016 (2000).CrossRefADSGoogle Scholar
  29. 29.
    E. Caffau, H.-G. Ludwig, M. Steffen, et al., Solar. Phys. 268, 255 (2011).CrossRefADSGoogle Scholar
  30. 30.
    T. W. R. Monroe, J. Meléndez, I. Ramírez, et al., Astrophys. J. Lett. 774, L32 (2013).CrossRefADSGoogle Scholar
  31. 31.
    A. M. Boesgaard and M. Tripicco, Astrophys. J. 302, L49 (1986).CrossRefADSGoogle Scholar
  32. 32.
    A. M. Boesgaard and J. R. King, Astrophys. J. 565, 587 (2002).CrossRefADSGoogle Scholar
  33. 33.
    A. M. Boesgaard, Astron. Soc. Pacific Conf. Ser. 336, 39 (2005).Google Scholar
  34. 34.
    A. M. Boesgaard, M. G. Lum, C. P. Deliyannis, et al., Astrophys. J. 830, id. 49 (2016).Google Scholar
  35. 35.
    L. S. Lyubimkov, D. L. Lambert, B. M. Kaminsky, et al., Mon. Not. Roy. Astron. Soc. 427, 11 (2012).Google Scholar
  36. 36.
    L. S. Lyubimkov and D. V. Petrov, Astrophysics 60, 333 (2017).CrossRefADSGoogle Scholar
  37. 37.
    A. G. W. Cameron and W. A. Fowler, Astrophys. J. 164, 111 (1971).CrossRefADSGoogle Scholar
  38. 38.
    C. Aguilera-Gómez, J. Chanamé, M. H. Pinsonneault, et al., Astrophys. J. 829, id. 127 (2016).Google Scholar
  39. 39.
    L. S. Lyubimkov, Astrophysics 56, 472 (2013).CrossRefADSGoogle Scholar
  40. 40.
    M. F. Nieva and N. Przybilla, Astron. Astrophys. 539, A143 (2012).CrossRefGoogle Scholar
  41. 41.
    L. Fossati, N. Castro, T. Morel, et al., Astron. Astrophys. 574, A20 (2015).CrossRefGoogle Scholar
  42. 42.
    L. S. Lyubimkov, Astrophysics 59, 472 (2016).Google Scholar
  43. 43.
    R. E. Luck and D. L. Lambert, Astrophys. J. 298, 782 (1985).CrossRefADSGoogle Scholar
  44. 44.
    L. S. Lyubimkov, D. L. Lambert, S. A. Korotin, et al., Mon. Not. Roy. Astron. Soc. 446, 3447 (2015).CrossRefADSGoogle Scholar

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© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Crimean Astrophysical ObservatoryRussian Academy of SciencesBakhchivandzhiRussia

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