Vendredi 18 Octobre 2002, à 14h, Paris, 77 avenue Denfert Rochereau, 14h
77 avenue Denfert Rochereau, Paris 14
Salle de l'Atelier, Observatoire de Paris
Dust shells around oxygen-rich Miras and long-period variable stars
Kyung Sook JEONG
Observatoire de Paris/LERMA
Résumé :
Circumstellar dust shells around cool pulsating late type stars are
the major sources for the replenishment of the interstellar medium
with processed material, in particular in the form of complex
molecules and of dust particles. The consistent description of these
dust forming circumstellar shells constitutes a non-linearly coupled
problem of hydrodynamics, thermodynamics, chemistry, dust formation,
growth and evaporation, and radiative transfer. Therefore, a
simultaneous solution of the complete system, including the dust
formation, is indispensable for a correct description of a
circumstellar dust shell.
In contrast to the carbon-rich situation, where mainly homogeneous
grains are formed, in an oxygen-rich gas almost all carbon is locked
up in the chemically inert CO molecule and therefore, grains can only be
formed from reactive molecules containing the remaining oxygen and
less abundant elements such as Fe, Si, Mg, S, Al, and Ti. In this
case, a heterogeneous composition of the emerging dust component has
to be expected.
In the talk, I will present consistent model calculations for
oxygen-rich circumstellar shells around Miras and long-period
variables which include a proper treatment of the dust formation
process.
