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Astron. Astrophys. 345, 315-320 (1999)

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On the applicability of the Rayleigh approximation for coated spheroids in the near-infrared

V.V. Somsikov and N.V. Voshchinnikov

Astronomical Institute, St. Petersburg University, Bibliotechnaya pl. 2, 198904 St. Petersburg-Peterhof, Russia

Received 27 July 1998 / Accepted 9 December 1998


Calculations of the extinction and polarization profiles in the wavelength range [FORMULA] 2.7-22 µm have been performed for silicate core - icy mantle spheroidal grains using the exact solution to the light scattering problem and the Rayleigh approximation.

It is concluded that the 10% accuracy of the Rayleigh approximation is guaranteed in the case of extinction (polarization) if the particle size does not exceed [FORMULA] within the 18 µm, 10 µm and 3 µm bands respectively, where r is the radius of a sphere with the same volume as a spheroid.

Key words: infrared: ISM: lines and bands – ISM: dust, extinction – polarization – scattering

Send offprint requests to: Nikolai Voshchinnikov (nvv@aispbu.spb.su)

This article contains no SIMBAD objects.


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© European Southern Observatory (ESO) 1999

Online publication: April 12, 1999