Modeling Dust Composition around the Carbon-Rich star W Orionis

Asymptotic Giant Branch (AGB) stars are major contributors of cosmic dust to the interstellar medium. The dust composition of a circumstellar shell is primarily determined by a star’s carbon to oxygen ratio (C/O). Carbon-rich stars are expected to have circumstellar shells dominated by amorphous carbon or graphitic carbon grains. With a C/O > 1, we can refer to W Ori as a carbon-rich giant. Using the radiative transfer code, DUSTY, we tested the effect of using different types of carbon dust, as well as metallic iron dust to generate the dust continuum observed in the spectrum of W Ori. All these models required a similar abundance of silicon carbide grains, to account for an infrared spectral feature around 11-micron. We use a wide set of observed parameters, including the light curve, C/O, mass-loss rate and expansion velocity to constrain our model inputs. Finally, we tested the limits and degeneracies of our modeled best fit parameters and the assumption embedded within our derived constraints (such as dust formation temperature). We present these results of this study of W Ori.