Presentation #130.01 in the session “Evolved stars”.
Carbon-rich evolved stars are major contributors of new elements and dust to the interstellar medium. These stars eject matter (dust and gas) via a combination of pulsation and radiation pressure. Using radiative transfer (RT) modeling we investigate dust formation and the dust shells around carbon-rich asymptotic giant branch (AGB) stars. As these stars pulsate in a fairly regular manner, we can observe how pulsation affects dust formation, using observations of the stars change in brightness with time (its light curve). Carbon-rich AGB star, R Sculptoris (R Scl), was observed spectroscopically by the Infrared Space Observatory (ISO) six times over the course of a pulsation cycle. We have used RT code, DUSTY, to model each of these spectra. To constrain the input parameters for the RT models we use different stellar/circumstellar parameters: C/O, mass-loss rate, spectral type, and light curve. From these quantities we estimate the star temperature at each point on the light curve as well as the pressure-temperature (P-T) space around the star. P-T conditions allow us to estimate the dust formation temperature as an input to DUSTY. We present the results of DUSTY modeling and what this demonstrates about dust formation over the course of a stellar pulsation cycle.