Research Papers (RG)

Permanent URI for this collectionhttp://localhost:4000/handle/11007/1768

Browse

Filters

20082

Settings

Author: search.filters.author.Gupta, RanjanSubject: search.filters.subject.Extinction

Search Results

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Composite interstellar grains and the 2175˚A feature
    (Organic Matter in Space Proceedings IAU Symposium, 2008-08-14) Vaidya, D.B.; Gupta, Ranjan
    We use discrete dipole approximation (DDA) to study the scattering properties of composite grains made up of host silicate spheroids and graphite inclusions. We calculate the extinction cross sections of the composite grains in the wavelength region 0.20–0.55 μm and study the extinction of the composite grains as a function of graphite inclusions. We present the composite grain model and discuss the results.
  • No Thumbnail Available
    Item
    Composite Interstellar Grains
    (Mon. Not. R. Astron. Soc, 2008-02-01) Vaidya, D.B.; Gupta, Ranjan; Snow, T.P
    A composite dust grain model which is consistent with the observed interstellar extinction and linear polarization is presented. The composite grain is made up of a host silicate spheroid and graphite inclusions. The extinction efficiencies of the composite spheroidal grains for three axial ratios are computed using the discrete dipole approximation (DDA). The interstellar extinction curve is evaluated in the spectral region 3.40–0.10μm using the extinction efficiencies of the composite spheroidal grains. The model extinction curves are then compared with the average observed interstellar extinction curve.We also calculate the linear polarization for the spheroidal composite grains at three orientation angles and find the wavelength of maximum polarization. Further, we estimate the volume extinction factor, an important parameter from the point of view of cosmic abundance, for the composite grain models that reproduce the average observed interstellar extinction. The estimated abundances derived from the composite grain models for both carbon and silicon are found to be lower than that are predicted by the bare silicate/graphite grain models but these values are still higher than that are implied from the recent ISM values.