Lithium dip

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The English-language term of the lithium dip describes a lower frequency of the element lithium in the atmospheres of main sequence stars with surface temperatures between 6300  K and 6900 K. The frequency of lithium and sometimes also beryllium is a factor of up to 100 lower than that of main sequence stars with a temperature of 300 K above and below the limit of the lithium dip .

Lithium is destroyed at temperatures of 2.5 MK by thermonuclear reactions inside stars. This leads to a depletion of lithium during the pre-main sequence phase and when the star is a subgiant afterwards . In these two phases, the convection zone extends from the surface to the core, which destroys lithium from the star's atmosphere in the core. The lithium dip does not occur in young stars as in the open star cluster of the Pleiades .

The under-abundance of lithium is considerably less pronounced in stars in close binary star systems . In these binary stars, the otherwise differential rotation of the stars is canceled by tidal forces and the stars rotate like rigid bodies in a first approximation. It is therefore assumed that the lithium dip is a result of rotationally-induced mixing of the star, which is not predicted by the standard models of stellar evolution. Alternative hypotheses lead the lithium dip back to diffusion , mass losses due to stellar winds and other forms of mixing of the stars.

Individual evidence

  1. ↑ Patrick Baugh, Jeremy R. King, Constantine P. Deliyannis, Ann Merchant Boesgaard: A Spectroscopic Analysis of the Eclipsing Short-Period Binary v505 Per and the Origin of the Lithium Dip . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1306.0644v1 .
  2. ^ Pascale Garaud, Peter Bodenheimer: Gyroscopic pumping of large-scale flows in stellar interiors, and application to Lithium Dip stars . In: Astrophysics. Solar and Stellar Astrophysics . 2010, arxiv : 1306.1618v1 .
  3. ↑ Ryan, SG & Deliyannis, CP: Lithium in Short-Period Tidally Locked Binaries: A Test of Rotationally Induced Mixing . In: Astrophysical Journal . tape 453 , 1995, pp. 819-836 .
  4. ^ Balachandran, S .: The Lithium Dip in M67: Comparison with the Hyades, Praesepe, and NGC 752 Clusters . In: Astrophysical Journal . tape 446 , 1995, pp. 203-227 .