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Projeto Observacional para 2017A - OI2017A-032
Autor: Stavros Akras
Título: The First optical polarimetric cataloque of symbiotic stars
Resumo: Scattering processes in symbiotic stars are expected to hide crucial information about the dynamic of these systems and produce significant degree of polarization. Only for a few SySts have been obtained polarimetric data almost 25 years ago. The main mechanisms that produce polarization can be (i) scattering by atomic or molecular hydrogen (Rayleigh and Raman scattering), (ii) atmospheric dust scattering and (iii) circumstellar dust scattering. These three mechanisms expect to have different wavelength dependences (Schulte-Ladbeck 1985). The D and D? type SySts show significant infrared excesses compared to the S-type SySts due to the present of dust (e.g. Angeloni et al. 2007,10, Phillips 2007). This raises the question whether these three types are polarimetrically different. Schulte-Ladbeck (1985) found that only 4 out of 13 S-type SySts are intrinsically polarized, whereas all the D-type (4 out of 4) are intrinsically polarized. But the sample was very small and new data are required for a larger sample of SySts. We propose to observe and colect optical (U,B,V,R and I) polarimetric data from a large number of SySts covering all the types.