CNO-driven winds of hot first stars

Jiri Krticka, Jiri Kubat

Masaryk University, Brno, Czech Republic
Astronomical Institute, Ondrejov, Czech Republic

During the evolution of first stars, the CNO elements may emerge on their
surfaces due to the mixing processes. Consequently, these stars may have winds
driven purely by CNO elements. We study the properties of such stellar winds
and discuss their influence on the surrounding environment. For this purpose,
we used our own NLTE models and tested which stellar parameters of the first
stars at different evolutionary stages result in CNO winds. If such winds are
possible, we calculate their hydrodynamic structure and predict their
parameters. We show that, while the studied stars do not have any wind driven
purely by hydrogen and helium, CNO driven winds exist in more luminous stars.
On the other hand, for very hot stars, CNO elements are too ionized to drive a
wind. In most cases the derived mass-loss rate is much less than calculated
with solar mixture of elements. This is because wind mass-loss rate in present
hot stars is dominated by elements heavier than CNO. We conclude that, until a
sufficient amount of these elements is created, the influence of line-driven
winds is relatively small on the evolution of hot stars (which are not close to
the Eddington limit).

Reference: A&A, in press
Status: Manuscript has been accepted