Spectroscopy of SMC Wolf-Rayet Stars Suggests that Wind-Clumping does not Depend on Ambient

author{S.V. Marchenkoaltaffilmark{1}, C. Foellmialtaffilmark{2,3}, A.F.J. Moffataltaffilmark{4},
F. Martinsaltaffilmark{5}, J.-C. Bouretaltaffilmark{6}, E. Depagnealtaffilmark{3,7}}

altaffiltext{1}{Department of Physics and Astronomy, Western Kentucky
University, 1906 College Heights Blvd., 11077, Bowling Green, KY
42101-1077; sergey.marchenko@wku.edu}
altaffiltext{2}{Laboratoire d'Astrophysique, Observatoire de Grenoble, BP 53,
38041 Grenoble Cedex 9, France; cfoellmi@eso.org}
altaffiltext{3}{European Southern Observatory, 3107 Alonso de Cordova, Casilla 19001,
Vitacura, Santiago, Chile}
altaffiltext{4}{D'epartement de Physique and
Observatoire du Mont M'egantic, Universit'e de Montr'eal, CP 6128,
Succursale Centre-Ville, Montr'eal, QC H3C 3J7, Canada; moffat@astro.umontreal.ca}
altaffiltext{5}{Max-Planck-Institut f"{u}r extraterrestrische Physik, Postfach 1312,
D-85741 Garching, Germany; martins@mpe.mpg.de}
altaffiltext{6}{Laboratoire d'Astrophysique de Marseille, Traverse du Siphon - BP 8,
13376 Marseille Cedex 12, France; jean-claude.bouret@oamp.fr}
altaffiltext{7}{Departamento de Astronomía y Astrof'{i}sica, Pontificia Universidad
Cat`{o}lica de Chile, Campus San Joaqu'{i}n, Vicu~{n}a Mackenna 4860 Casilla 306,
Santiago 22, Chile; edepagne@eso.org}

The mass-loss rates of hot, massive, luminous stars are considered a decisive
parameter in shaping the evolutionary tracks of such stars and influencing the interstellar
medium on galactic scales. The small-scale structures (clumps) omnipresent in
such winds may reduce empirical estimates of mass-loss rates by an evolutionarily significant factor
of $geq 3$. So far, there has been no {it {direct}} observational evidence that
wind-clumping may persist at the same level in environments with a low
ambient metallicity, where the wind-driving opacity is reduced. Here we report
the results of time-resolved spectroscopy of three presumably single Population I Wolf-Rayet
stars in the Small Magellanic Cloud, where the ambient metallicity is $sim 1/5 Z_sun$.
We detect numerous
small-scale emission peaks moving outwards in the accelerating parts of the stellar winds.
The general properties of the moving features, such as their velocity dispersions,
emissivities and average accelerations, closely match the corresponding characteristics
of small-scale inhomogeneities in the winds of Galactic Wolf-Rayet stars.

Reference: ApJL
Status: Manuscript has been accepted

Weblink: http://gemini.tccw.wku.edu:8080/~sergey/ms.pdf


Email: sergey@astro.wku.edu