Grassitelli, L.; Fossati, L.; Simón-Diáz, S.; Langer, N.; Castro, N.; Sanyal, D.
Bibliographical reference
The Astrophysical Journal Letters, Volume 808, Issue 1, article id. L31, 6 pp. (2015).
Description
The major mass fraction of the envelope of hot luminous stars is
radiatively stable. However, the partial ionization of hydrogen, helium,
and iron gives rise to extended sub-surface convection zones in all of
them. In this work, we investigate the effect of the pressure induced by
the turbulent motion in these zones based on the mixing-length theory,
and we search for observable consequences. We find that the turbulent
pressure fraction can amount up to ∼ 5% in OB supergiants and up to
∼ 30% in cooler supergiants. The resulting structural changes are,
however, not significantly affecting the evolutionary tracks compared to
previous calculations. Instead, a comparison of macroturbulent
velocities derived from high-quality spectra of OB stars with the
turbulent pressure fraction obtained in corresponding stellar models
reveals a strong correlation between these two quantities. We discuss a
possible physical connection and conclude that turbulent pressure
fluctuations may drive high-order oscillations, which—as
conjectured earlier—manifest themselves as macroturbulence in the
photospheres of hot luminous stars.
Related projects
The IACOB project: A new Era in the Study of Galactic OB Stars
IACOB is an ambitious long-term project whose main scientific goal is to provide an unprecedented empirical overview of the main physical properties of Galactic massive O- and B-type stars which can be used as definitive anchor point for our theories of stellar atmospheres, winds, interiors and evolution of massive stars