Spectrophotometric variability of the magnetic CP star 56 Arietis in spectral region from 1950 to 3200 Å

Sokolov, N. A.

doi:10.1007/s10509-010-0355-5

Cited by 3 publications

(4 citation statements)

References 23 publications

(23 reference statements)

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“…The light variations in this region are mainly caused by silicon (c.f., Fig. 2, and Sokolov 2006and Sokolov , 2010. The overall agreement between the predicted and observed light curves in this region indicates that silicon abundances are well mapped.…”

Section: Narrow-band Uv Variationssupporting

confidence: 53%

“…9). The amplitudes of the observed light curves in this region and their shapes are a result of the inhomogeneous surface distribution of silicon, iron, and chromium (see also Sokolov 2010). Even more subtle effects, like the mutual shift of the light maxima at wavelengths 2550 Å and 2800 Å, can be explained by our models.…”

Section: Narrow-band Uv Variationsmentioning

confidence: 67%

“…Vertical abundance stratification is observed in some CP stars (e.g., Ryabchikova 2004). Sokolov (2010) proposed that the vertical abundance stratification may influence the light variability. Our test calculations confirmed these expectations.…”

Section: Vertical Abundance Stratificationmentioning

confidence: 99%

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Modelling of the ultraviolet and visual SED variability in the hot magnetic Ap star CU Virginis

Krtička

Mikulášek

Lüftinger

et al. 2011

A&A

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Context. The spectral energy distribution (SED) in chemically peculiar stars may be significantly affected by their abundance anomalies. The observed SED variations are usually assumed to be a result of inhomogeneous surface distribution of chemical elements, flux redistribution and stellar rotation. However, the direct evidence for this is still only scarce. Aims. We aim to identify the processes that determine the SED and its variability in the UV and visual spectral domains of the heliumweak star CU Vir. Methods. We used the TLUSTY model atmospheres calculated for the appropriate surface chemical composition to obtain the emergent flux and predict the rotationally modulated flux variability of the star. Results. We show that most of the light variations in the vby filters of the Strömgren photometric system are a result of the uneven surface distribution of silicon, chromium, and iron. Our models are only able to explain a part of the variability in the u filter, however. The observed UV flux distribution is very well reproduced, and the models are able to explain most of the observed features in the UV light curve, except for the region 2000−2500 Å, where the amplitude of the observed light variations is higher than predicted. The variability observed in the visible is merely a faint gleam of that in the UV. While the amplitude of the light curves reaches only several hundredths of magnitude in the visual domain, it reaches about 1 mag in the UV. Conclusions. The visual and UV light variability of CU Vir is caused by the flux redistribution from the far UV to near UV and visible regions, inhomogeneous distribution of the elements and stellar rotation. Bound-free transitions of silicon and bound-bound transitions of iron and chromium contribute the most to the flux redistribution. This mechanism can explain most of the rotationally modulated light variations in the filters centred on the Paschen continuum and on the UV continuum of the star CU Vir. However, another mechanism(s) has to be invoked to fully explain the observed light variations in the u filter and in the region 2000−2500 Å.

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Section: Narrow-band Uv Variationssupporting

confidence: 53%

Section: Narrow-band Uv Variationsmentioning

confidence: 67%

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Modelling of the ultraviolet and visual SED variability in the hot magnetic Ap star CU Virginis

Krtička

Mikulášek

Lüftinger

et al. 2011

A&A

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“…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. The connection between the abundance spots and flux redistribution has emerged as a natural explanation of the rotationally modulated light curves of CP stars, but the details of this relation still have to be determined on a solid theoretical basis.…”

Section: Introductionmentioning

confidence: 86%

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 helium-peculiar staraCentauri

Sokolov

2012

Monthly Notices of the Royal Astronomical Society

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The spectrophotometric variability of the classical magnetic chemically peculiar star a Cen in the ultraviolet spectral region from 1150 to 3100 Å is investigated. This study is based on archival International Ultraviolet Explorer data obtained at various phases of the rotational cycle. The light variations in wavelengths shorter than λ1616 Å are mainly in antiphase to the light variations in the longer-wavelength region. The brightness of the star in the spectral region λλ1616-1640 Å is constant over the period of rotation, which means that a so-called 'null wavelength region' exists over these wavelengths. There is also a second 'null wavelength region' in the spectrum of a Cen. According to our investigation, the semi-amplitude of the light variations is practically zero over the period of rotation in the spectral region λλ1244-1343 Å. The exception is the light variation in the depressions at λλ1265 and 1300 Å, which are formed by resonance lines of silicon. However, the fluxes are constant at the cores of some features and in small depressions. An explanation for the light variations of a Cen is flux redistribution through bound-free and bound-bound silicon transitions combined with an inhomogeneous surface distribution of silicon on the stellar surface. The influence of other elements on the flux redistribution is discussed.

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Spectrophotometric variability of the magnetic CP star 56 Arietis in spectral region from 1950 to 3200 Å

Cited by 3 publications

References 23 publications

Modelling of the ultraviolet and visual SED variability in the hot magnetic Ap star CU Virginis

Modelling of the ultraviolet and visual SED variability in the hot magnetic Ap star CU Virginis

Modelling the light variability of the Ap starε Ursae Majoris

Ultraviolet variability of the helium-peculiar staraCentauri

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