Participant 3 (P3)
==================
Prof. N.V. Voshchinnikov - Astronomy Department and Sobolev Astronomical
Institute, St. Petersburg University, RU
Dr. V.B. Il'in - Sobolev Astronomical Institute, St. Petersburg
University, RU
M.S. Prokop'eva - 24 years old; Astronomy Department, St. Petersburg
University, RU
D.A. Semenov - 22 years old; Astronomy Department, St. Petersburg
University, RU
The head of the team, Prof. Voshchinnikov, has undertook a number of researches
on light scattering theory, radiative transfer, and their astrophysical
applications. Many of these works were made together with Dr. Il'in and other
colleagues. Recent investigations of the members of this team on the subject of
the project are as follows:
Task 1 (Light scattering theory)
A new approach to solution of the light scattering problem for homogeneous
and coated confocal spheroids in the frame of the Separation of variables method
has been suggested by Farafonov and then developed by Voshchinnikov & Farafonov
("Optical properties of spheroidal particles." Astrophys. Space Science,
v. 204, 19, 1993), Farafonov, Voshchinnikov, and Somsikov ("Light scattering by
a core-mantle spheroidal particle." Appl. Opt., v. 35, 5412, 1996),
Voshchinnikov ("Electromagnetic scattering by homogeneous and coated spheroids:
calculations using the separation of variables method." J. Quant. Spectrosc.
Rad. Transfer, v. 55, 627, 1996).
First steps to the realization of a new solution to the light scattering problem
based on the T-matrix method were made by Farafonov, Il'in, and Henning ("A new
solution of the light scattering problem for axisymmetric particles." J. Quant.
Spectrosc. Rad. Transfer, v. 63, 205, 1999).
The applicability of the Rayleigh and quasistatic approximations for spheroidal
particles was considered by Somsikov & Voshchinnikov ("On the applicability of
the Rayleigh approximation for coated spheroids in the near-infrared." Astron.
Astrophys., v. 345, 315, 1999) and Voshchinnikov & Farafonov ("On applicability
of quasistatic and Rayleigh approximations for spheroidal particles." Opt.
Spectrosc., 1999, in press).
A numerical code for multi-layered spheres and a new "layered-sphere" EMT were
developed by Voshchinnikov & Mathis ("Calculating cross sections of composite
interstellar grains." Astrophys. J., 1999, v. 526, N1 - the LANL-preprint
astro-ph/9908240).
Task 3 (Electronic database)
A database of optical constants for astronomy was created in a joint work with
colleagues from Jena (Henning, Il'in, Krivova, Michel, and Voshchinnikov "WWW
database of optical constants for astronomy." Astron. Astrophys. Suppl., v. 136,
405, 1999). It has a free access via the Internet: http://www.astro.spbu.ru/
JPDOC/entry.html.
A comparison of different computational methods and some benchmark results were
presented by Hovenier, Lumme, Mishchenko, Voshchinnikov et al. ("Computations
of scattering matrices of four types of non-spherical particles using diverse
methods." J. Quant. Spectrosc. Rad. Transfer, v. 55, 695, 1996) and by
Voshchinnikov, Il'in, Henning et al. ("Extinction and polarization of radiation
by absorbing spheroids: shape/size effects and some benchmarks." J. Quant.
Spectrosc. Rad. Transfer, 1999, in press - the LANL-preprint astro-ph/9908241).
Task 4 (Polarized radiation transfer)
A new version of the Monte Carlo method (the method of symmetrized trajectories)
for polarized radiation transfer calculations in axisymmetric dust shells was
developed by Voshchinnikov & Karjukin ("Multiple scattering of polarized
radiation in circumstellar dust shells." Astron. Astrophys., v. 288, 883, 1994).
Task 5 (Astrophysical applications)
An application of the model of homogeneous spheroids to the interstellar
extinction and polarization was done by Voshchinnikov & Farafonov ("Optical
properties of spheroidal particles." Astrophys. Space Science, v. 204, 19,
1993). A first step to the development of a new model of composite interstellar
grains was made by Voshchinnikov & Mathis ("Calculating cross sections of composite interstellar
grains." Astrophys. J., 1999, v. 526, N1, in press - the LANL-preprint
astro-ph/9908240).
The particle shape effects on the temperature of interstellar grains were
estimated by Voshchinnikov, Semenov, and Henning ("The temperature of
non-spherical interstellar grains." Astron. Astrophys., 1999, in press - the
LANL-preprint astro-ph/9908235).
Applications of Monte Carlo simulations to the calculation of the circumstellar
extinction and polarization curves were made by Voshchinnikov, Molster, and The
("Circumstellar extinction in the shells of pre-main-sequence stars." Astron.
Astrophys., v. 312, 243, 1996) and Voshchinnikov et al. ("Monte Carlo simulation
of light scattering in the envelopes of young stars." Astron. Astrophys.,
v. 294, 547, 1995; "Dust shells around Herbig Ae/Be stars." Astron. Reports.
v. 42, 46, 1998).
Polarimetric maps and infrared fluxes of young stars were modelled using Monte
Carlo simulations of polarized radiation transfer by Krivova, Il'in et al.
("Dust around Herbig Ae stars: additional constraints from their photometric and
polarimetric variability." in: M.E. Kress, A.G.G.M. Tielens, and Y.J. Pendleton
(eds.), From Stardust to Planetesimals: Contributed Papers, NASA-CP #3343, 37,
1997; "Dust shells around Herbig Ae/Be stars with Algol-like minima: modelling
of photometric observations." Astron. Letters, v. 23, 791, 1997; "Dust grains
around Herbig Ae/Be stars: porous, cometary-like grains?." Icarus, 1999, in
press).
The motion of non-spherical dust grains in the shells of evolved stars due to
radiation pressure was considered by Il'in & Voshchinnikov ("Radiation pressure
on non-spherical dust grains in envelopes of late-type giants." Astron.
Astrophys. Suppl., v. 128, 187, 1998).
P3 team:
3.1. Voshchinnikov N.V., Farafonov V.G. (1993)
Optical properties of spheroidal particles.
Astrophysics & Space Science, v. 204, 19-86.
3.2. Voshchinnikov N.V., Karjukin V.V. (1994)
Multiple scattering of polarized radiation in circumstellar dust shells.
Astronomy & Astrophysics, v. 288, 883-896.
3.3. Voshchinnikov N.V., Molster F.J., The P.S. (1996)
Circumstellar extinction in the shells of pre-main-sequence stars.
Astronomy & Astrophysics, v. 312, 243-255.
3.4. Farafonov V.G., Voshchinnikov N.V., Somsikov V.V. (1996)
Light scattering by a core-mantle spheroidal particle.
Applied Optics, v. 35, 5412-5426.
3.5. Voshchinnikov N.V. (1996)
Electromagnetic scattering by homogeneous and coated spheroids:
calculations using the separation of variables method.
Journal of Quantitative Spectroscopy & Radiative Transfer, v. 55, 627-636.
3.6. Hovenier J.W., Lumme K., Mishchenko M.I., Voshchinnikov N.V. et al. (1996)
Computations of scattering matrices of four types of non-spherical
particles using diverse methods.
Journal of Quantitative Spectroscopy & Radiative Transfer, v. 55, 695-705.
3.7. Il'in V.B., Voshchinnikov N.V. (1998)
Radiation pressure on non-spherical dust grains in envelopes of late-type
giants.
Astronomy & Astrophysics Supplement, v. 128, 187-196.
3.8. Somsikov V.V., Voshchinnikov N.V. (1999)
On the applicability of the Rayleigh approximation for coated spheroids in
the near-infrared.
Astronomy & Astrophysics, v. 345, 315-320.
3.9. Henning Th., Il'in V.B., Krivova N.A., Michel B., Voshchinnikov N.V. (1999)
WWW database of optical constants for astronomy.
Astronomy & Astrophysics Supplement, v. 136, 405-406.
3.10.Farafonov V.G., Il'in V.B., Henning Th. (1999)
A new solution of the light scattering problem for axisymmetric particles.
Journal of Quantitative Spectroscopy & Radiative Transfer, v. 63, 205-215.