A&A 418, 639-648 (2004)

DOI: 10.1051/0004-6361:20040090

## Maximum mass-loss rates of line-driven winds of massive stars: The effect of rotation and an application to Carinae

**C. Aerts**

^{1}, H. J. G. L. M. Lamers^{2, 3}and G. Molenberghs^{4}^{1}Institute of Astronomy, Catholic University of Leuven, Celestijnenlaan 200 B, 3001 Leuven, Belgium

^{2}Astronomical Institute, Utrecht University, PO Box 80000, 3508 TA Utrecht, The Netherlands

^{3}SRON Laboratory, for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands

^{4}Center for Statistics, Limburgs Universitair Centrum, Universitaire Campus, Building D, 3590 Diepenbeek, Belgium

(Received 31 March 2003 / Accepted 10 January 2004)

** Abstract **

We investigate the effect of rotation on the maximum mass-loss rate
due to an optically-thin radiatively-driven wind according to a formalism which
takes into account the possible presence of any instability at the base of the
wind that might increase the mass-loss rate. We include the Von Zeipel effect
and the oblateness of the star in our calculations. We determine the maximum
surface-integrated mass that can be lost from a star by line driving as a
function of rotation for a number of relevant stellar models of massive OB stars
with luminosities in the range of
. We also
determine the corresponding maximum loss of angular momentum. We find that
rotation increases the maximum mass-loss rate by a moderate factor for stars far
from the Eddington limit as long as the ratio of equatorial to critical velocity
remains below 0.7. For higher ratios, however, the temperature, flux and
Eddington factor distributions change considerably over the stellar surface such
that extreme mass loss is induced. Stars close to the Eddington-Gamma limit
suffer extreme mass loss already for a low equatorial rotation velocity. We
compare the maximum mass-loss rates as a function of rotation velocity with
other predicted relations available in the literature which do not take into
account possible instabilities at the stellar surface and we find that the
inclusion thereof leads to extreme mass loss at much lower rotation rates. We
present a scaling law to predict maximum mass-loss rates. Finally, we provide a
mass-loss model for the LBV
Carinae that is able to explain the large
observed current mass-loss rate of ~
yr
^{-1} but that
leads to too low wind velocities compared to those derived from observations.

**Key words:**stars: early-type

**--**stars: mass-loss

**--**stars: winds, outflows

**--**stars: evolution

**--**methods: statistical

**--**stars: individual: Car

Offprint request: C. Aerts, conny@ster.kuleuven.ac.be

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*ESO 2004*