Ultraviolet variability of the magnetic chemically peculiar star 56 Arietis

Sokolov, N. A.

doi:10.1111/j.1365-2966.2006.11037.x

Cited by 9 publications

(12 citation statements)

References 20 publications

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“…If the proposed mechanism of the light variability is correct, the studied star should be variable also in the UV region and the observed light curve in the far UV region should be in antiphase with the optical and near-UV light curve. Indeed, a similar behaviour was found for other CP stars CU Vir and 56 Ari by Sokolov (2000Sokolov ( , 2006.…”

Section: Discussionsupporting

confidence: 84%

The light variability of the helium strong star HD 37776 as a result of its inhomogeneous elemental surface distribution

Krtička¹,

Mikulášek²,

Zverko

et al. 2007

A&A

100

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We simulate light curves of the helium strong chemically peculiar star HD 37776 assuming that the observed periodic light variations originate as a result of inhomogeneous horizontal distribution of chemical elements on the surface of a rotating star. We show that chemical peculiarity influences the monochromatic radiative flux, mainly due to bound-free processes. Using the model of the distribution of silicon and helium on HD 37776 surface, derived from spectroscopy, we calculate a photometric map of the surface and consequently the uvby light curves of this star. Basically, the predicted light curves agree in shape and amplitude with the observed ones. We conclude that the basic properties of variability of this helium strong chemically peculiar star can be understood in terms of the model of spots with peculiar chemical composition.

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Section: Discussionsupporting

confidence: 84%

The light variability of the helium strong star HD 37776 as a result of its inhomogeneous elemental surface distribution

Krtička¹,

Mikulášek²,

Zverko

et al. 2007

A&A

100

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“…6, 7, we predict that the star should have a flux minimum in the short-wavelength λ 1600 Å part of the spectrum during the visible light maximum and vice versa. A similar antiphase behaviour of the short-wavelength UV and optical light curves has been reported for other CP stars (e.g., Sokolov 2006). Unfortunately, there is no UV light curve of HR 7224 available.…”

Section: Uv Variationssupporting

confidence: 81%

The nature of the light variability of the silicon star HR 7224

Krtička¹,

Mikulášek

Henry

et al. 2009

A&A

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Context. Although photometric variations of chemically peculiar (CP) stars are frequently used to determine their rotational periods, the detailed mechanism of their light variability remains poorly understood. Aims. We simulate the light variability of the star HR 7224 using the observed surface distribution of silicon and iron. Methods. We used the TLUSTY model atmospheres calculated for the appropriate silicon and iron abundances to obtain the emergent flux and to predict the rotationally modulated light curve of the star. We also obtained additional photometric measurements and employed our own regression procedure to derive a more precise estimate of the light elements. Results. We show that the light variation of the star can be explained as a result of i) the uneven surface distribution of the elements, ii) the flux redistribution from the ultraviolet to the visible part of the spectrum, and iii) rotation of the star. We show that the silicon bound-free transitions and iron bound-bound transitions provide the main contribution to the flux redistribution, although an additional source of opacity is needed. We confirm that numerous iron lines significantly contribute to the well-known depression at 5200 Å and discuss the connection between iron abundance and the value of peculiarity index a. Conclusions. The uneven surface distribution of silicon and iron is able to explain most of the rotationally modulated light variation in the star HR 7224.

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“…Thus, the fluxes in these two spectral regions should display an anti-phase behaviour. This has been experimentally already reported for some CP stars (see Sokolov 2000Sokolov , 2006, for CU Vir and 56 Ari, respectively). Light curve modelling of HD 37776 and HR 7224 has also successfully predicted this characteristic signature of stellar spots.…”

Section: Uv Variationsmentioning

confidence: 49%

“…If so, there may be a point (or points or even regions, see Mikulášek et al 2007b) in the spectra where the flux remains almost unchanged, and vary more or less in anti-phase on both sides from it. This region, called a "null wavelength region", has been noted and confirmed by a number of studies (see, for example, Leckrone 1974;Molnar 1973;Jamar 1977;Sokolov 2000Sokolov , 2006. However, that the truly "null wavelength region" in stars with more complex light curves may not exist (Sokolov 2006(Sokolov , 2010.…”

Section: Introductionmentioning

confidence: 95%

Modelling the light variability of the Ap starε Ursae Majoris

Shulyak

Krtička

Mikulášek

et al. 2010

A&A

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Aims. We simulate the light variability of the Ap star ε 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 ε 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 ε 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 Å 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 β 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 ε UMa.

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Ultraviolet variability of the magnetic chemically peculiar star 56 Arietis

Cited by 9 publications

References 20 publications

The light variability of the helium strong star HD 37776 as a result of its inhomogeneous elemental surface distribution

The light variability of the helium strong star HD 37776 as a result of its inhomogeneous elemental surface distribution

The nature of the light variability of the silicon star HR 7224

Modelling the light variability of the Ap starε Ursae Majoris

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