Complex structure of the magnetic field of the CP star HD32633

Glagolevskij, Yu. V.; Gerth, E.

doi:10.1134/s199034130803005x

Cited by 9 publications

(12 citation statements)

References 4 publications

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“…This is a variant with four monopoles, as in the cases of the stars HD32633 and HD37776 [5,6]. The parameters of this model are listed…”

Section: Version II Of the Shifted Dipole Modelmentioning

confidence: 99%

Complex structure of the magnetic field of the CP-Star HD142301

Glagolevskij

2010

Astrophysics

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Models of the magnetic field of the He-w star HD142301 are constructed. Observational data are well described by the model of a dipole shifted by 0.6 stellar radii transverse to the axis. The phase dependence of the HeI λ4026Å line, however, corresponds better to a model assuming the presence of four monopoles (or two dipoles) shifted by 0.4 stellar radii from the center. The distance between the monopoles in both models is comparable to the star's radius, which indicates that the source of the magnetic field is "long" dipoles, rather than "point" dipoles.

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“…This is a variant with four monopoles, as in the cases of the stars HD32633 and HD37776 [5,6]. The parameters of this model are listed…”

Section: Version II Of the Shifted Dipole Modelmentioning

confidence: 99%

Complex structure of the magnetic field of the CP-Star HD142301

Glagolevskij

2010

Astrophysics

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“…These facts, as discussed above, very strongly suggest that either the detailed metal abundance distributions or the field geometry, or probably both, are complex. This star appears to belong to the small sample of stars, including HD 32633 (Glagolevskij & Gerth 2008), HD 37776 (Kochukhov et al 2011), HD 133880 (Landstreet 1990), HD 137509 (Kochukhov 2006), and τ Sco (Donati et al 2006) in which the magnetic field may depart in an important way from the generally dipolar topology of the magnetic fields of most Ap stars. (The field and surface He distribution of the outstandingly peculiar magnetic He-strong star HD 37776 have recently been mapped by Kochukhov et al 2011, and the resulting map reveals a quite astonishing degree of complexity.)…”

Section: Refinement Of the Rotation Periodmentioning

confidence: 99%

Magnetic field and atmospheric chemical abundances of the magnetic Ap star HD 318107

Bailey

Landstreet

Bagnulo³

et al. 2011

A&A

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Context.A new generation of powerful and efficient spectropolarimeters has recently been used to provide the first sample of magnetic Ap stars of accurately known ages. Modelling of these data offer the possibility of significant new insights into the physics and main sequence evolution of these remarkable stars. Aims. New spectra have been obtained with the ESPaDOnS spectropolarimeter, and are supplemented with unpolarised spectra from the ESO UVES, UVES-FLAMES, and HARPS spectrographs, of the very peculiar large-field magnetic Ap star HD 318107, a member of the open cluster NGC 6405 and thus a star with a well-determined age. The available data provide sufficient material with which to re-analyse the first-order model of the magnetic field geometry and to derive chemical abundances of Si, Ti, Fe, Nd, Pr, Mg, Cr, Mn, O, and Ca. Methods. The models were obtained using ZEEMAN, a program which synthesises spectral line profiles for stars that have magnetic fields. The magnetic field structure was modelled with a low-order colinear multipole expansion, using coefficients derived from the observed variations of the field strength with rotation phase. The abundances of several elements were determined using spectral synthesis. After experiments with a very simple model of uniform abundance on each of three rings of equal width in co-latitude and symmetric about the assumed magnetic axis, we decided to model the spectra assuming uniform abundances of each element over the stellar surface. Results. The new magnetic field measurements allow us to refine the rotation period of HD 318107 to P = 9.7088 ± 0.0007 days. Appropriate magnetic field model parameters were found that very coarsely describe the (apparently rather complex) field moment variations. Spectrum synthesis leads to the derivation of mean abundances for the elements Mg, Si, Ca, Ti, Cr, Fe, Nd, and Pr. All of these elements except for Mg and Ca are strongly overabundant compared to the solar abundance ratios. There is considerable evidence of non-uniformity, for example in the different values of B z found using lines of different elements. Conclusions. The present data set, while limited, is nevertheless sufficient to provide a useful first-order assessment of both the magnetic and surface abundance properties of HD 318107, making it one of the very few magnetic Ap stars of well-known age for which both of these properties have been studied.

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“…The braking hypothesis is supported by the following property of CP stars: the lower the mass of a star is, the more its average rotation velocity Vsini differs from that of normal stars [24].…”

Section: Discussionmentioning

confidence: 76%

“…On the other hand, CP stars with higher rotational velocities are more prevalent among normal stars [24]. This last property corresponds to the hypothesis that the lower the initial rotation velocity of a star is when it is created, the higher the probability is that it will become chemically peculiar.…”

Section: Discussionmentioning

confidence: 91%

Magnetic field model for slowly rotating CP-stars. γEqu= HD201601

Glagolevskij

Gerth²

2006

Astrophysics

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A magnetic field model is constructed for the extremely slow rotator γEqu based on measurements of its magnetic field over many years and using the "magnetic charge" method. An analysis of γEqu and of all the data accumulated up to the present on the magnetic field parameters of chemically peculiar stars leads to some interesting conclusions, of which the main ones are: the fact that the axis of rotation and the dipole axis are not parallel in γEqu and the other slowly rotating magnetic stars which we have studied previously is one of the signs that the braking of CP stars does not involve the participation of the magnetic field as they evolve "to the main sequence." The axes of the magnetic field dipole in slow rotators are oriented arbitrarily with respect to their axes of rotation. The substantial photometric activity of these CP stars also argues against these axes being close. The well-known absence of sufficiently strong magnetic fields in the Ae/Be Herbig stars also presents difficulties for the hypothesis of "magnetic braking" in the "pre-main sequence" stages of evolution. The inverse relation between the average surface magnetic field Bs and the rotation period P is yet another fact in conflict with the idea that the magnetic field is involved in the braking of CP stars. We believe that angular momentum loss involving the magnetic field can hardly have taken place during evolution immediately prior "to the main sequence," rather the slow rotation of CP stars most likely originates from protostellar clouds with low angular momentum. Some of the slowly rotating stars have a central dipole magnetic field configuration, while others have a displaced dipole configuration, where the displacement can be toward the positive or the negative magnetic pole.

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Complex structure of the magnetic field of the CP star HD32633

Cited by 9 publications

References 4 publications

Complex structure of the magnetic field of the CP-Star HD142301

Complex structure of the magnetic field of the CP-Star HD142301

Magnetic field and atmospheric chemical abundances of the magnetic Ap star HD 318107

Magnetic field model for slowly rotating CP-stars. γEqu= HD201601

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