Circumstellar Dust Shell around Long-Period Variables: II. Theoretical lightcurves of C-stars

J.M. Winters, A.J. Fleischer, A. Gauger and E. Sedlmayr

Astronomy & Astrophysics, Vol. 290, 623-633 (1994)

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Abstract:

Theoretical lightcurves of long-period and Mira variables are presented.

Based on dynamical models of circumstellar dust shells (CDS), which include time-dependent hydrodynamics and a detailed treatment of the processes of formation, growth and evaporation of carbon grains, frequency-dependent radiative transfer calculations have been carried out which yield the synthetic infrared lightcurves of these dust shell models.

It turns out that the discrete structure of the CDS due to the periodic formation of new dust layers decisively influences the shape of the lightcurves by producing e.g. intermediate extrema. This is demonstrated in detail for one model. Furthermore, dust shell models are presented whose lightcurves exhibit the superposition of two different oscillations: The oscillation with the period of the interior pulsation is superposed by an oscillation with a longer period which is produced by the dynamical structure of the CDS. Similar features are present in observed lightcurves, which indicates that our, nevertheless preliminary, modelling approach shows promise for interpreting the optical appearance of Miras and long-period variables.

Keywords:

hydrodynamics - radiative transfer - stars: carbon - circumstellar matter - stars: late-type