English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

In this paper we study the effects of inclusions and porosities on theemission properties of silicate grains and compare the model curves with theobserved infrared emission from circumstellar dust.  We calculate the absorption efficiency of the composite grain, made up of ahost silicate oblate spheroid and inclusions of ice/graphite/or voids, in thespectral region 5.0-25.0$\mu m$. The absorption efficiencies of the compositespheroidal oblate grains for three axial ratios are computed using the discretedipole approximation (DDA). We study the absorption as a function of the volumefraction of the inclusions and porosity. In particular, we study the variationin the $10\mu m$ and $18\mu m$ emission features with the volume fraction ofthe inclusions and porosities. We then calculate the infrared fluxes for thesecomposite grains at several dust temperatures (T=200-350K) and compare themodel curves with the average observed IRAS-LRS curve, obtained forcircumstellar dust shells around oxygen rich M-type stars. The model curves arealso compared with two other individual stars.  The results on the composite grains clearly indicate that the silicatefeature at 10$\mu m$ shifts with the volume fraction of graphite inclusions.The feature does not shift with the porosity. Both the features do not show anybroadening with the inclusions or porosity. The absorption efficiencies of thecomposite grains calculated using DDA and Effective Medium Approximation (EMA)do not agree. The composite grain models presented in this study need to becompared with the observed IR emission from the circumstellar dust around a fewmore stars.

Infrared Emission from the Composite Grains: Effects of Inclusions and Porosities on the 10 and 18 $\mu m$ Features