Humphreys-Davidson border
The Humphreys-Davidson limit is the empirically determined maximum luminosity in which a star can exist in hydrostatic equilibrium. It was first described by the American astronomers R. M. Humphreys and K. Davidson in 1979.
Above the Humphreys-Davidson line, only stars are visible during eruptions such as B. Supernovae have been observed. If the luminosity exceeds this value, there will be rapid and variable mass losses through stellar winds, as in the case of the luminous blue variables . To explain the maximum luminosity limit, the following hypotheses have been made:
- a lowering of the Eddington limit
- outward pressure due to strong turbulence
- a Rayleigh-Taylor instability due to density inversion.
When simulating massive stars, it was pointed out that around the Humphreys-Davidson limit, the atmosphere of these stars becomes unstable to pulsations . The rate of growth of the vibrations increases a hundred times faster than the star can restore its hydrostatic equilibrium , the strong stellar wind at the Humphreys-Davidson boundary could therefore be a consequence of pulsation instability.
literature
- ^ Humphreys, RM & Davidson, K .: Studies of luminous stars in nearby galaxies. III - Comments on the evolution of the most massive stars in the Milky Way and the Large Magellanic Cloud . In: The Astrophysical Journal . tape 232 , no. 1 , 1979, p. 409-420 .
- ↑ Glatzel, W. & Kiriakidis, M .: Stability of Massive Stars and the Humphreys / Davidson limit . In: Monthly Notice of the Royal Astronomical Society . tape 263 , no. 2 , 1995, p. 375-384 .
- ^ Hideyuki Saio: Linear analyzes for the stability of radial and nonradial oscillations of massive stars . In: Astrophysics. Solar and Stellar Astrophysics . 2010, arxiv : 1011.4729v1 .