Effective temperatures of Ap stars

Sokolov, N. A.

doi:10.1051/aas:1998226

Cited by 19 publications

(19 citation statements)

References 18 publications

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“…Sokolov (1998) estimated the value of T eff = 12 460 K from the slope of the energy distribution in the Balmer continuum near the Balmer jump. Adelman and Rayle (2000) determined the values of T eff = 12 850 K, log g = 4.0, and v micro = 2 km s −1 from the fit of the energy distribution in visual spectral region with the prediction of the metal-rich models.…”

Section: Identification Of the Observed Depressions And Featuresmentioning

confidence: 99%

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

Sokolov

2010

Astrophys Space Sci

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The spectrophotometric variability of the magnetic CP star 56 Arietis (56 Ari) in the ultraviolet spectral region from 1950 to 3200 Å is investigated. This study is based on the archival International Ultraviolet Explorer data obtained at different phases of the rotational cycle. The brightness of 56 Ari is not constant in the investigated wavelengths over the whole rotational period. The monochromatic light curves continuously change their shape with wavelength. This indicates that we do not observe a truly 'null wavelength region' where the monochromatic light curve has a zero amplitude. Probably, an uneven surface distribution of silicon and iron mainly influences the flux redistribution from the far-UV to near-UV spectral regions, although additional sources of opacity may be involved. The redistribution of the flux at phase 0.25 is connected with the nonuniform distribution of silicon on the stellar surface of 56 Ari. On the other hand, the redistribution of the flux at phase 0.65 is quite complex, because there are additional blocking and redistribution of the flux by iron lines in the near-UV spectral region.

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Section: Identification Of the Observed Depressions And Featuresmentioning

confidence: 99%

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

Sokolov

2010

Astrophys Space Sci

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“…Kupka et al (1996) analysed high‐resolution spectra of α Cir and estimated the fundamental parameters using Geneva and Strömgren photometric indices, the Balmer lines and a detailed classical analysis of several iron‐peak lines. Sokolov (1998) proposed a new method to estimate T eff of roAp stars based on the slope of the continuum near the Balmer jump and found a high T eff for α Cir. Kochukhov & Bagnulo (2006) analysed a large sample of magnetic chemically peculiar stars and they used Geneva indices to estimate the fundamental parameters of α Cir.…”

Section: Fundamental Parameters Of α Cirmentioning

confidence: 99%

The fundamental parameters of the roAp star α Circini

Bruntt

North

Cunha

et al. 2008

Monthly Notices of the Royal Astronomical Society

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We have used the Sydney University Stellar Interferometer to measure the angular diameter of α Cir. This is the first detailed interferometric study of a rapidly oscillating A (roAp) star, α Cir being the brightest member of its class. We used the new and more accurate Hipparcos parallax to determine the radius to be 1.967 ± 0.066 R⊙. We have constrained the bolometric flux from calibrated spectra to determine an effective temperature of 7420 ± 170 K. This is the first direct determination of the temperature of an roAp star. Our temperature is at the low end of previous estimates, which span over 1000 K and were based on either photometric indices or spectroscopic methods. In addition, we have analysed two high‐quality spectra of α Cir, obtained at different rotational phases and we find evidence for the presence of spots. In both spectra we find nearly solar abundances of C, O, Si, Ca and Fe, high abundance of Cr and Mn, while Co, Y, Nd and Eu are overabundant by about 1 dex. The results reported here provide important observational constraints for future studies of the atmospheric structure and pulsation of α Cir.

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“…Many attempts to determine effective temperatures of mCP stars can be found in literature. Unfortunately, most of them are based on photometry or, at best, on visual parts of SED (Hauck & North 1993; Sokolov 1998; Adelman & Rayle 2000). As a result, they are prone to systematic errors arising from peculiar SED and uncertain reddening corrections.…”

Section: Introductionmentioning

confidence: 99%

Effective temperatures of magnetic chemically peculiar stars from full spectral energy distributions

Lipski

Stępień

2008

Monthly Notices of the Royal Astronomical Society

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New determinations of effective temperatures of 23 magnetic, chemically peculiar (mCP) stars were obtained from a fit of metal‐enhanced model atmospheres to the observed spectral energy distributions (SED) from ultraviolet (UV) to red. Temperatures of four more CP stars without magnetic measurements were also obtained, of which three show light variations characteristic of magnetic variables, and the fourth may possibly be normal. The root‐mean‐square (rms) method was used to fit the theoretical SED to the observations corrected for reddening if necessary, with metallicity and effective temperature as the fitting parameters. Gravity was assumed to be equal to log g= 4 for main‐sequence stars and to log g= 3 for two giants in the considered sample. Equal weights were given to the UV part and visual part of SED. An attempt was made to obtain a three‐parameter fit (with reddening included) to the observed SED of HD 215441. It turned out that the three‐parameter fit gave spurious results due to correlations among the parameters. We could determine the reddening of that star only by assuming that the metallicity of the model is known, hence reducing the number of fitting parameters to two. Independently of the formal quality of fit resulting from the rms method applied to the whole SED, the quality of fit was additionally checked for each star by determination of the temperature from the best‐fitting model atmosphere to the UV part and the visual part of SED separately. Both temperatures should be close to one another if the global best‐fitting model satisfactorily describes the full observed SED. This is the case for about a half of the investigated stars but the difference exceeds 750 K for the remaining stars with the extreme values above 2000 K. Possible reasons for such discrepancies are discussed. New revised calibrations of effective temperature and bolometric corrections of mCP stars in terms of reddening free Strömgren indices are given.

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Effective temperatures of Ap stars

Cited by 19 publications

References 18 publications

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

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

The fundamental parameters of the roAp star α Circini

Effective temperatures of magnetic chemically peculiar stars from full spectral energy distributions

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