A^{2} Canum Venaticorum and the Oblique-Rotator Theory

Pyper, D. M.

doi:10.1086/190193

Cited by 84 publications

(40 citation statements)

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“…Taking into account the distance to α 2 CVn, d = 35.2 ± 1.1 pc which follows from the revised Hipparcos parallax (van Leeuwen 2007), and adopting V = 2.89 ± 0.04 from Pyper (1969), we find the absolute visual magnitude M V = 0.16 ± 0.08. For the temperature T eff = 11 600 ± 500 K and the bolometric correction BC = −0.42 measured by Lipski & Stȩpień (2008) we obtain L = 101 ± 12 L and R = 2.49 ± 0.26 R assuming M bol = 4.75 for the Sun (Bessell 2000) and using an uncertainty of 0.1 for the bolometric correction of α 2 CVn.…”

Section: Physical Properties Of α 2 Cvnmentioning

confidence: 87%

“…Atmospheric parameters α 2 CVn (12 CVn A, HD 112413, HR 4915, HIP 63125) was the first star given the "A-type peculiar" classification (Maury & Pickering 1897) and is a prototype of spectrum variable stars. It was classified as A0pSiEuHg by Cowley et al (1969) and was targeted by many notable magnetic and spectrum variability studies (Babcock & Burd 1952;Pyper 1969;Cohen 1970;Borra & Landstreet 1977), including early attempts to reconstruct maps of abundance spots and magnetic field with the Doppler Imaging technique (Goncharskii et al 1983;Khokhlova & Pavlova 1984;Glagolevskii et al 1985).…”

Section: Physical Properties Of α 2 Cvnmentioning

confidence: 99%

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Magnetic Doppler imaging ofα²Canum Venaticorum in all four Stokes parameters

Kochukhov¹,

Wade

2010

A&A

114

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Context. Strong organized magnetic fields have been studied in the upper main sequence chemically peculiar stars for more than half a century. However, only recently have observational methods and numerical techniques become sufficiently mature to allow us to record and interpret high-resolution four Stokes parameter spectra, leading to the first assumption-free magnetic field models of these stars. Aims. Here we present a detailed magnetic Doppler imaging analysis of the spectropolarimetric observations of the prototypical magnetic Ap star α 2 CVn. This is the second star for which the magnetic field topology and horizontal chemical abundance inhomogeneities have been inferred directly from phase-resolved observations of line profiles in all four Stokes parameters, free from the traditional assumption of a low-order multipolar field geometry.Methods. We interpret the rotational modulation of the circular and linear polarization profiles of the strong Fe ii and Cr ii lines in the spectra of α 2 CVn recorded with the MuSiCoS spectropolarimeter. The surface abundance distributions of the two chemical elements and a full vector map of the stellar magnetic field are reconstructed in a self-consistent inversion using our state-of-the-art magnetic Doppler imaging code Invers10. Results. We succeeded in reproducing most of the details of the available spectropolarimetric observations of α 2 CVn with a magnetic map which combines a global dipolar-like field topology with localized spots of higher field intensity. We demonstrate that these small-scale magnetic structures are inevitably required to fit the linear polarization spectra; however, their presence cannot be inferred from the Stokes I and V observations alone. We also found high-contrast surface distributions of Fe and Cr, with both elements showing abundance minima in the region of weaker and topologically simpler magnetic field. Conclusions. Our magnetic Doppler imaging analysis of α 2 CVn and previous results for 53 Cam support the view that the upper main sequence stars can harbour fairly complex surface magnetic fields which resemble oblique dipoles only at the largest spatial scales. Spectra in all four Stokes parameters are absolutely essential to unveil and meaningfully characterize this field complexity in Ap stars. We therefore suggest that understanding magnetism of stars in other parts of the H-R diagram is similarly incomplete without investigation of their linear polarization spectra.

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Section: Physical Properties Of α 2 Cvnmentioning

confidence: 87%

Section: Physical Properties Of α 2 Cvnmentioning

confidence: 99%

Magnetic Doppler imaging ofα²Canum Venaticorum in all four Stokes parameters

Kochukhov¹,

Wade

2010

A&A

114

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“…In the past such studies were predominantly based on the Fourier analysis of the variation of the disk-integrated quantities, such as equivalent widths, radial velocities and longitudinal magnetic field (e.g. Deutsch 1958;Pyper 1969). More recent investigations, such as the one presented by Kuschnig et al (1999), attempt to reconstruct surface abundance distributions with the Doppler Imaging (DI) method.…”

Section: Introductionmentioning

confidence: 99%

“…Since the beginning of the 20th century much effort has been devoted to the description of the variations of its radial velocity, line strengths and longitudinal magnetic field. Previous detailed investigations of the magnetic field topology and chemical inhomogeneities (Pyper 1969;Khokhlova & Pavlova 1984) were based on a separate, inconsistent analysis of the magnetic and abundance observables. These studies provided only a coarse estimate of the magnetic geometry of α 2 CVn and yielded maps showing surface variations of equivalent width, but not absolute abundance distributions.…”

Section: Introductionmentioning

confidence: 99%

Doppler Imaging of stellar magnetic fields

Kochukhov¹,

Piskunov²,

Ilyin

et al. 2002

A&A

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Abstract. We used the new magnetic Doppler Imaging code to reconstruct the magnetic field geometry and surface abundance distributions for the classical magnetic CP star α 2 CVn. High-resolution spectropolarimetric observations in the Stokes I and V parameters were collected with the SOFINéchelle spectrograph at the Nordic Optical Telescope. This superb observational material in combination with the advanced modelling technique allowed to achieve the first simultaneous self-consistent mapping of the vector magnetic field and the abundance distributions of six chemical elements. In recovering the stellar magnetic distribution no prior assumptions about the field geometry or strength were made. Instead, we restricted possible solutions of the inverse problem by means of the multipolar regularization method which searches for the field map close to a general non-axisymmetric multipolar configuration but allows departures from this geometry if that is required by the observational data. We found that the magnetic field of α 2 CVn is dominated by a dipolar component and has a minor quadrupole contribution. The surface distributions of the chemical species form symmetric patterns which closely follow the magnetic geometry. This discovery constitutes one of the first direct observational constraints on the horizontal diffusion processes acting in the upper envelope of a strongly magnetized stellar atmosphere. In addition to the extensive magnetic Doppler Imaging analysis, we derived new accurate estimates of the atmospheric parameters and basic physical properties of α 2 CVn using the energy distribution, hydrogen line profiles and the recent Hipparchos parallax.

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“…Given a sufficient time span for the observations, many mCP stars are likely to be found to be slowing their rotation. But given the rotational constancy for a few mCP stars such as α 2 CVn whose period was first found early in the 20th century (Guthnick & Prager 1914;Pyper 1969), the differences from constancy are likely to be very small.…”

Section: Introductionmentioning

confidence: 99%

On the rotation of the chemically peculiar magnetic star 56 Arietis

Adelman

Malanushenko

Ryabchikova

et al. 2001

A&A

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Abstract. This study used extensive sets of phase resolved photometric and spectroscopic data obtained by the authors and supplemented by that from the literature to investigate the light and equivalent width variations of the mCP star 56 Ari. Its rotational period is found to be increasing at a rate of about 2 s per 100 years. In addition there is evidence for a second period whose length is about 5 years which is attributed to the precession of the axis of rotation.

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A^{2} Canum Venaticorum and the Oblique-Rotator Theory

Cited by 84 publications

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Magnetic Doppler imaging ofα²Canum Venaticorum in all four Stokes parameters

Magnetic Doppler imaging ofα²Canum Venaticorum in all four Stokes parameters

Doppler Imaging of stellar magnetic fields

On the rotation of the chemically peculiar magnetic star 56 Arietis

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A^{2} Canum Venaticorum and the Oblique-Rotator Theory

Cited by 84 publications

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Magnetic Doppler imaging ofα2Canum Venaticorum in all four Stokes parameters

Magnetic Doppler imaging ofα2Canum Venaticorum in all four Stokes parameters

Doppler Imaging of stellar magnetic fields

On the rotation of the chemically peculiar magnetic star 56 Arietis

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Resources

About

Magnetic Doppler imaging ofα²Canum Venaticorum in all four Stokes parameters

Magnetic Doppler imaging ofα²Canum Venaticorum in all four Stokes parameters