Sarah Massalkhi MSc Defense – University of Copenhagen

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Sarah Massalkhi MSc Defense

Title: Circumstellar Dust Shells around Evolved Massive Stars

Supervisor: Anja C. Andersen


This project focuses on estimating the temperatures and masses of ejected circumstellar
dust shells using a sample of evolved massive stars. Aperture photometry was performed on the sample at mid- and far-infrared wavelengths. The measured flux densities were fitted by a modified blackbody which accounts for an emissivity spectral index, . The latter is influenced by the properties of dust grains, such as grain size and composition. In this thesis, three different values of = 1, 1.5 and 2 were investigated. The best-fit dust temperatures were found and used to estimate the masses of the ejected dust. Moreover,  three different dust compositions were explored when estimating the masses. I conclude that the dust temperatures are influenced by the properties of dust grains. In addition, the dust masses are revealed dependency on the composition of the grains. The derived dust masses infer low-mass nebulae ejected by these type of stars.

Thesis here >>