An improved mass-loss description for dust-driven superwinds and tip-AGB evolution models

Details An improved mass-loss description for dust-driven superwinds and tip-AGB evolution models An improved mass-loss description for dust-driven superwinds and tip-AGB evolution models

Mar 2002

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002a%26a...384..452w&link_type=abstract

Astronomy and Astrophysics, v.384, p.452-459 (2002)

Astronomy and Astrophysics

Astrophysics

85

Stars: Carbon, Stars: Circumstellar Matter, Stars: Evolution, Stars: Interiors, Stars: Late-Type, Stars: Mass Loss

Scientific paper

We derive an improved description of dust-driven stellar mass-loss for the cool winds of carbon-rich tip-AGB stars. We use pulsating wind models in which the mass loss is driven by radiation pressure on dust grains, for C-rich chemistry. From a larger set of these models, selected for representative dynamical (pulsational velocity amplitude Delta v, period P) and chemical (the epsilonC/epsilonO abundance ratio) input parameters, an improved approximative mass-loss formula has been derived which depends only on the stellar parameters (effective temperature Teff, luminosity L and mass M). Due to the detailed consideration of the chemistry and the physics of the dust nucleation and growth processes, there is a particularly strong dependence of the mass-loss rate dot {M} (in Msun/yr) on Teff: log {dot {M}} = 8.86 - 1.95 * log {M/{Msun}} - 6.81 * log {T/K} + 2.47 * log {L/{Lsun}}. The dependence of the model mass-loss on the pulsational period has explicitly been accounted for in connection with the luminosity dependence, by applying an observed period-luminosity relation for C-rich Miras. We also apply the improved mass-loss description to our evolution models, and we revisit their tip-AGB mass-loss histories and the total masses lost, in comparison to our earlier work with a preliminary mass-loss description. While there is virtually no difference for the models in the lower mass range of consideration (Mi = 1.0 to ~ 1.3 Msun), we now find more realistic, larger superwind mass-loss rates for larger stellar masses: i.e., dot {M} between ~ 0.4 and 1.0 x 10-4 Msun/yr for Mi between 1.85 and 2.65 Msun, removing between 0.6 and 1.2 Msun, respectively, during the final 30 000 yrs on the tip-AGB.

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