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Modelling the light variability of the Ap star epsilon Ursae Majoris
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.
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2010 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 524, no 3, A66- p.Article in journal (Refereed) Published
Abstract [en]

Aims. We simulate the light variability of the Ap star epsilon UMa using the observed surface distributions of Fe, Cr, Ca, Mn, Mg, Sr, and Ti obtained with the help of the Doppler imaging technique. Methods. Using all photometric data available, we specified light variations of epsilon UMa 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. Results. The rotational period of epsilon UMa is refined to 5.(d)088631(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 contribute significantly to the amplitude of the observed light variability. In general, we find very good agreement between theory and observations. We confirm the important role of Fe and Cr in determining the magnitude of the well-known depression around 5200 angstrom by analyzing the peculiar a-parameter. Finally, we show that the abundance spots of considered elements cannot explain the observed variabilities in near UV and beta index, which probably have other causes. Conclusions. The inhomogeneous surface distribution of chemical elements can explain most of the observed light variability of the A-type CP star epsilon UMa.

Place, publisher, year, edition, pages
2010. Vol. 524, no 3, A66- p.
Keyword [en]
stars: chemically peculiar, stars: variables: general, stars: atmospheres, stars: individual: epsilon UMa
National Category
Physical Sciences
URN: urn:nbn:se:uu:diva-139480DOI: 10.1051/0004-6361/201015094ISI: 000284625300056OAI: oai:DiVA.org:uu-139480DiVA: diva2:381394
Available from: 2010-12-27 Created: 2010-12-27 Last updated: 2012-10-11Bibliographically approved

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Kochukhov, Oleg
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