Modelling the light variability of the Ap star epsilon Ursae Majoris

Abstract

We simulate the light variability of the Ap star epsUMa using the observed surface distributions of Fe, Cr, Ca, Mn, Mg, Sr and Ti obtained with the help of Doppler Imaging technique. Using all photometric data available we specified light variations of epsUMa modulated by its rotation from far UV to IR. We employed the LLmodels stellar model atmosphere code to predict the light variability in different photometric systems. The rotational period of epsUMa is refined to 5d088631(18). It is shown that the observed light variability can be explained as a result of the redistribution of radiative flux from the UV spectral region to the visual caused by the inhomogeneous surface distribution of chemical elements. Among seven mapped elements, only Fe and Cr significantly contribute to the amplitude of the observed light variability. In general, we find a very good agreement between theory and observations. We confirm the important role of Fe and Cr to the magnitude of the well-known depression around 5200 Å through the analysis of the peculiar $a$-parameter. Finally, we show that the abundance spots of considered elements cannot explain the observed variability in near UV and $\beta$ index which are likely due to some other causes. The inhomogeneous surface distribution of chemical elements can explain most of the observed light variability of the A-type CP star epsUMa.

Accepted in A&A, 10 pages, 9 figures, 3 tables

References in corpus (6)

• The light variability of the helium strong star HD 37776 as a result of its inhomogeneous elemental surface distribution
• Chemical stratification in the atmosphere of Ap star HD 133792. Regularized solution of the vertical inversion problem
• Isotopic anomaly and stratification of Ca in magnetic Ap stars
• Theoretical analysis of the atmospheres of CP stars. Effects of the individual abundance patterns
• The Lorentz force in atmospheres of CP stars: $\theta$ Aurigae
• Spectrophotometric variability of the magnetic CP star 56 Arietis in spectral region from 1950 to 3200 A

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