Optical polarimetry and modelling of the polar FL Ceti / Polarimetria óptica e modelagem da polar FL Ceti

AUTOR(ES)

Karleyne Medeiros Gomes da Silva

DATA DE PUBLICAÇÃO

2009

RESUMO

Cataclysmics variables (CV) are binary systems of short orbital period composed by a white dwarf and a red dwarf star that fills its Roche lobe and transfers matter to the white dwarf. In polars, a particular subclass of CVs, matter follows the magnetic field lines of the white dwarf (about 10^7 Gauss on the surface) and gives rise an accretion column. Near the surface, a shock is produced. This region is responsible for most emission from polars. This work is a study of the eclipsing polar FL Ceti using flux and polarization data obtained with the 1.60 m telescope of Observatório do Pico dos Dias in the R_c and I_c bands. We have obtained light curves and the first polarization curves for FL Cet in high state of brightness. Earlier studies have pointed out that FL Cet has two accretion columns. Our data indicate that one of them is always visible. To estimate the physical and geometrical parameters of the emitting regions of FL Cet, we have used the new code CYCLOPS (CYCLotron On Polar Shocks). It calculates the optical emission from polars considering the cyclotronic emitting process in inhomogeneous post-shock regions. The code can include one or two regions near the white dwarf surface, which can have different physical properties. With CYCLOPS, we could not find a good fit for the flux and circular polarization using the model parameters with values restricted to those found in the literature. We have, therefore, increased the range of parameters. In this situation, the flux and circular polarization of the system could be fitted independently, but the simultaneous fits were not satisfactory. Changes of the scenario and a better contraints on the geometrical parameters of the system can help in finding an adequate model to FL Cet.

ASSUNTO(S)

cataclysmic variables astronomical astronomical models binary stars polarimetria. modelagem polarimetry variáveis cataclísmicas estrelas binárias

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