HD 178892 – a cool Ap star with extremely strong magnetic field

Ryabchikova, T. A.; Kochukhov, O.; Kudryavtsev, D. O.; Romanyuk, I. I.; Semenko, E. A.; Bagnulo, S.; Curto, G. Lo; North, P.; Sachkov, Mikhail

doi:10.1051/0004-6361:200500222

Cited by 32 publications

(33 citation statements)

References 14 publications

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“…This means that the surface magnetic field of HD 178892 should be exceptionally high. Later, this conclusion was confirmed in the paper by Ryabchikova et al (2006). From the measurements of magnetically split lines they established the presence of a strong magnetic field ( B s = 17.5 kG).…”

Section: Introductionmentioning

confidence: 59%

“…It is necessary to stress the fact that our instrumental setup is practically the same as in the earlier paper by Ryabchikova et al (2006) with the study of HD 178892, except for one change. From May 2010 we started to use a new detector based on the EEV CCD 42-90.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

“…The working spectral range was approximately the same as in the paper by Ryabchikova (2006), the spectral resolution R was about 40 000. Such an instrumental setup also guarantees a high compatibility with older results.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

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Magnetic properties of three cool CP stars with strong fields

2011

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The study of magnetic fields of cool chemically peculiar stars with effective temperatures less than 10 000 K is very important to understand the nature of their magnetism. We present new results of a long-term spectroscopic monitoring of the well-known magnetic star HD 178892. The analysis of spectra taken with the Russian 6-m telescope has revealed a periodic variation of the surface magnetic field from 17 to 23 kG. A revised rotational period of HD 178892 was extracted from the mean longitudinal field: 8.2549 days. We have continued the study of the components of the magnetic binary BD +40• 175 started by V. Elkin at SAO RAS. Our measurements of magnetically splitted lines in the spectra of each component show the presence of strong magnetic fields in both components. The surface field in the case of the component A was about 14 kG at three different epochs. The component B possesses a slightly weaker field: Bs varies from 9 to 11 kG. A preliminary analysis of the chemical abundances allows us to make an assumption about the roAp nature of both components of BD +40• 175.

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Section: Introductionmentioning

confidence: 59%

Section: Observations and Data Reductionmentioning

confidence: 99%

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Magnetic properties of three cool CP stars with strong fields

2011

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“…Landstreet 1992; Mathys et al 1997;Hubrig et al 2004Hubrig et al , 2005Wade et al 2000). They can however be stronger as demonstrated by Hubrig et al (2005) and Ryabchikova et al (2006) who detected magnetic fields stronger than 20 kG in cool Ap stars.…”

Section: The Magnetic Ap Starsmentioning

confidence: 91%

New light on the driving mechanism in roAp stars

Théado

Dupret

Noels

et al. 2008

A&A

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Context. Observations suggest that a relationship exists between the driving mechanism of roAp star pulsations and the heavy element distribution in these stars. Aims. We attempt to study the effects of local and global metallicity variations on the excitation mechanism of high order p-modes in A star models. Methods. We developed stellar evolutionary models to describe magnetic A stars with different global metallicity or local metal accumulation profiles. These models were computed with CLES ("Code Liègeois d'évolution stellaire"), and the stability of our models was assessed with the non-adiabatic oscillation code MAD. Results. Our models reproduce the blue edge of the roAp star instability strip, but generate a red edge hotter than the observed one, regardless of metallicity. Surprisingly, we find that an increase in opacity inside the driving region can produce a lower amount of driving, which we refer to as the "inverse κ-mechanism".

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“…The "spectro-polarimetric" methods exploit the additional recording of the circular polarization with respect to the wavelength. This enables one to obtain a detailed map of the field [5] through a separation of its components parallel or perpendicular to the line of sight.…”

Section: Introductionmentioning

confidence: 99%

Characterization of anomalous Zeeman patterns in complex atomic spectra

Pain

Gilleron

2012

Phys. Rev. A

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The modeling of complex atomic spectra is a difficult task, due to the huge number of levels and lines involved. In the presence of a magnetic field, the computation becomes even more difficult. The anomalous Zeeman pattern is a superposition of many absorption or emission profiles with different Zeeman relative strengths, shifts, widths, asymmetries and sharpnesses. We propose a statistical approach to study the effect of a magnetic field on the broadening of spectral lines and transition arrays in atomic spectra. In this model, the σ and π profiles are described using the moments of the Zeeman components, which depend on quantum numbers and Landé factors. A graphical calculation of these moments, together with a statistical modeling of Zeeman profiles as expansions in terms of Hermite polynomials are presented. It is shown that the procedure is more efficient, in terms of convergence and validity range, than the Taylor-series expansion in powers of the magnetic field which was suggested in the past. Finally, a simple approximate method to estimate the contribution of a magnetic field to the width of transition arrays is proposed. It relies on our recently published recursive technique for the numbering of LS-terms of an arbitrary configuration.

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HD 178892 – a cool Ap star with extremely strong magnetic field

Cited by 32 publications

References 14 publications

Magnetic properties of three cool CP stars with strong fields

Magnetic properties of three cool CP stars with strong fields

New light on the driving mechanism in roAp stars

Characterization of anomalous Zeeman patterns in complex atomic spectra

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