Prof. L.B.F.M. Waters - Astronomical Institute "Anton Pannekoek", University of Amsterdam, NL and Institute for Astronomy, Catholic University of Leuven, Leuven, BE
Dr. A. de Koter - Astronomical Institute "Anton Pannekoek", University of Amsterdam, NL
F.J. Molster - Astronomical Institute "Anton Pannekoek", University of Amsterdam, NL
J. Bouwman - Astronomical Institute "Anton Pannekoek", University of Amsterdam, NL
C. Kemper - Astronomical Institute "Anton Pannekoek", University of Amsterdam, NL
This team is formed by Prof. Waters (the head of the team and the co-ordinator of the project) and his colleagues who specialize in ground and space observations (in particular, those with Infrared Space Observatory) of various cosmic dusty objects and their interpretation. Some of their researches have been made in a cooperation with the participants from Jena (P2) and Petersburg (P3). Recent papers of the Amsterdam team members on the subject of the project are as follows:
Task 3 (Electronic database)
In a joint work with colleagues from Jena, the absorption coefficients of olivines and pyroxenes with different Mg/Fe ratios were measured by Jaeger, Molster, Dorschner, Henning, Mutschke, and Waters ("Steps toward interstellar silicate mineralogy. IV. The crystalline revolution." Astron. Astrophys., 339, 904, 1998). The data were included in the Database of Optical Constants created by Henning, Il'in, Krivova, Michel, and Voshchinnikov ("WWW database of optical constan ts for astronomy." Astron. Astrophys. Suppl., 136, 405, 1999).
Task 4 (Polarized radiation transfer)
Calculations of linear polarization due to single Thompson scattering in a disk model were performed and analytical expressions for the relation between polarization and infrared excess as a function of model parameters for edge-on disks of classical Be stars were derived in the paper of Waters & Marlborough ("Constraints on Be star wind geometry by linear polarization and IR excess." Astron. Astrophys., 256, 195, 1992).
A program for calculations of the emergent flux from a spherical shell surrounding a single or binary star was developed in the University of Amsterdam (see http://www.astro.uva.nl/~dekoter/).
Task 5 (Astrophysical applications)
The Monte Carlo method to treat the polarized radiative transfer in dust shells was applied to young stars by Molster ("Modelling of circumstellar extinction and polarization." Master's thesis, University of Amsterdam, 1995) and by Voshchinnikov, Molster, and The ("Circumstellar extinction in the shells of pre-main-sequence stars." Astron. Astrophys., 312, 243, 1996).
Several emission features at wavelengths between 20 and 45 micron were found with the Short Wavelength Spectrometer (SWS) on board of the ISO in spectra of the dust shells around evolved oxygen-rich stars by Waters, Molster et al. ("Mineralogy of oxygen-rich dust shells." Astron. Astrophys., 315, L361, 1996). The emission peaks were tentatively identified with crystalline forms of silicates such as pyroxene and olivine.
The continuum-subtracted ISO SWS spectrum of the source AFGL 4106 was compared with simple optically thin model spectra calculated for olivine and pyroxene samples by Jaeger, Molster, Dorschner, Henning, Mutschke, and Waters ("Steps toward interstellar silicate mineralogy. IV. The crystalline revolution." Astron. Astrophys., 339, 904, 1998).
ISO-SWS spectroscopy of the cool dusty envelopes surrounding two planetary nebulae with [WC] central stars, BD+30 3639 and He 2-113 was discussed by Waters, Beintema, Zijlstra, de Koter, Molster, Bouwman et al. ("Crystalline silicates in planetary nebulae with [WC] central stars." Astron. Astrophys., 331, L61, 1998). It was found that the lambda < 15 micron region was dominated by a rising continuum with prominent emission from C-rich dust (Polycyclic Aromatic Hydrocarbons, PAHs), while the long wa velength part showed narrow solid state features from crystalline silicates.
Infrared observations of the Red Rectangle were presented by Waters et al. ("An oxygen-rich dust disk surrounding an evolved star in the Red Rectangle." Nature, 391, 868, 1998). They revealed the presence of oxygen-rich material: prominent emission bands from crystalline silicates and absorption lines arising from carbon dioxide. The oxygen-rich material is located in the circumbinary disk.
ISO observations of gas and dust in the reflection nebula Ced 201 were analyzed by Kemper et al. ("Far-infrared and submillimeter observations and physical models of the reflection nebula Cederblad 201." Astrophys. J., 515, 649, 1999). The contribution of very small grains to the photoelectric heating rate was estimated and used to constrain the total abundance of PAHs and small grains.
SWS-ISO observations of the dusty circumstellar disk surrounding the isolated young Fe star HD 142527 were discussed by Malfait, Waelkens, Bouwman, de Koter, and Waters ("The ISO spectrum of the young star HD 142527." Astron. Astrophys., 345, 181, 1999). Two dust populations were discriminated: a warm component which was dominated by very strong silicate emission at 10 micron and a cool component, of which the spectrum was dominated by O-rich dust features. Besides silicates, crystal line water-ice and hydrous silicates - which had been detected in interplanetary dust particles - were found to be present in the cold circumstellar environment as well.
There are many other recent researches of this team members on the project subject. One can find their results for instance via the NASA Astronomical Data System (ADS).
Ten recent publications on the subject of the project: