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Intrinsic polarization of Wolf-Rayet stars due to the rotational modulation of the stellar wind

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ABDELLAOUI Slah KRTIČKA Jiří KURFÜRST Petr

Rok publikování 2021
Druh Článek v odborném periodiku
Časopis / Zdroj arXiv e-prints
Fakulta / Pracoviště MU

Přírodovědecká fakulta

Citace
www https://arxiv.org/abs/2021arXiv211106785A
Klíčová slova stars: Wolf-Rayet – stars: rotation – polarization – stars: winds, outflows
Popis Fast rotating Wolf-Rayet stars are expected to be progenitors of long duration gamma-ray bursts. However, the observational test of this model is problematic. Spectral lines of Wolf-Rayet stars originate in expanding stellar wind, therefore a reliable spectroscopical determination of their rotational velocities is difficult. Intrinsic polarization of Wolf-Rayet stars due to the rotational modulation of the stellar wind may provide an indirect way to determine the rotational velocities of these stars. However, detailed wind models are required for this purpose. We determine the intrinsic polarization of Wolf-Rayet stars from hydrodynamical wind models as a function of rotational velocity. We used 2.5D hydrodynamical simulations to calculate the structure of rotating winds of Wolf-Rayet stars. The simulations account for the deformation of the stellar surface due to rotation, gravity darkening, and nonradial forces. From the derived models, we calculated the intrinsic stellar polarization. The mass loss rate was scaled to take realistic wind densities of Wolf-Rayet stars into account. The hydrodynamical wind models predict a prolate wind structure, which leads to a relatively low level of polarization. Even relatively large rotational velocities are allowed by observational constrains. The obtained wind structure is similiar to that obtained previously for rotating optically thin winds. Derived upper limits of rotational velocities of studied Wolf-Rayet stars are not in conflict with the model of long duration gamma-ray bursts

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