Light-curve variation caused by accretion column switching stellar hemispheres

Cemeljic, Miljenko and Siwak, Michal (2020) Light-curve variation caused by accretion column switching stellar hemispheres. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 491 (1). pp. 1057-1063. ISSN 0035-8711

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Abstract

We investigate switching of the accretion column between the stellar hemispheres in the magnetosphere of a star with the dipole magnetic field aligned with the stellar rotation axis. We show that such switching can produce 'hiccups' in the observed light curves. The intensity of emitted radiation from the stellar surface as seen by distant observers is computed from our two-dimensional axisymmetric viscous and resistive magnetohydrodynamic numerical simulations. This result is used to construct a three-dimensional model of a star with the ring-shaped hotspots from the accretion columns at the stellar surface. We compute the intensity from such hotspots. To obtain a non-axisymmetric model with arc-shaped hotspots, we remove a ring section in the azimuthal direction from the hotspots and compute the intensity of the radiated emission. Such models can be used to relate physical parameters in the simulations to the observations. We show an example with the intensity computed from our model compared to observational light curve.

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