Detecting and modelling the magnetic field of the<i>β</i> Cephei star V 2052 Ophiuchi

Neiner, C.; Alécian, E.; Briquet, Maryline; Floquet, M.; Frémat, Y.; Martayan, C.; Thizy, O.

doi:10.1051/0004-6361/201117941

Cited by 42 publications

(62 citation statements)

References 20 publications

(18 reference statements)

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“…In Fig. , the phase of minimum rotational light variation coincides with the minimum magnetic field strength and minimum UV spectral line equivalent width, as determined by Neiner et al (). In B 1, v and B there is also a double maximum, as in the UV line strength.…”

Section: Discussionsupporting

confidence: 77%

“…Besides the detection of a second, non‐radial, pulsation mode, these authors could derive an accurate rotation period of 3.638 833 ± 0.000 003 d. V2052 Oph also possesses a dipole magnetic field. Based on new data of superior quality, Neiner et al () determined that

B_{pol} \approx 400 G

, that the magnetic field is likely off‐centred and that He patches are present close to the magnetic poles. Because of the presence of a radial pulsation mode (that allows the determination of the mean stellar density), and of the known rotation period that makes it spin about twice as fast as the most ‘rapidly' rotating seismically well‐studied β Cep star (12 Lac; Desmet et al ), it was deemed worthwhile to devote a large observational effort to V2052 Oph.…”

Section: Introductionmentioning

confidence: 99%

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A multisite photometric study of two unusual β Cep stars: the magnetic V2052 Oph and the massive rapid rotator V986 Oph

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Shobbrook

Uytterhoeven³

et al. 2012

Monthly Notices of the Royal Astronomical Society

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We report a multisite photometric campaign for the β Cep stars V2052 Oph and V986 Oph. 670 h of high‐quality differential photoelectric Strömgren, Johnson and Geneva time‐series photometry was obtained with eight telescopes on five continents during 182 nights. Frequency analyses of the V2052 Oph data enabled the detection of three pulsation frequencies, the first harmonic of the strongest signal, and the rotation frequency with its first harmonic. Pulsational mode identification from analysing the colour amplitude ratios confirms the dominant mode as being radial, whereas the other two oscillations are most likely l = 4. Combining seismic constraints on the inclination of the rotation axis with published magnetic field analyses we conclude that the radial mode must be the fundamental mode. The rotational light modulation is in phase with published spectroscopic variability, and consistent with an oblique rotator for which both magnetic poles pass through the line of sight. The inclination of the rotation axis is 54° < i < 58° and the magnetic obliquity 58° < β < 66°. The possibility that V2052 Oph has a magnetically confined wind is discussed. The photometric amplitudes of the single oscillation of V986 Oph are most consistent with an l = 3 mode, but this identification is uncertain. Additional intrinsic, apparently temporally incoherent light variations of V986 Oph are reported. Different interpretations thereof cannot be distinguished at this point, but this kind of variability appears to be present in many OB stars. The prospects of obtaining asteroseismic information for more rapidly rotating β Cep stars, which appear to prefer modes of higher l, are briefly discussed.

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Section: Discussionsupporting

confidence: 77%

B_{pol} \approx 400 G

Section: Introductionmentioning

confidence: 99%

A multisite photometric study of two unusual β Cep stars: the magnetic V2052 Oph and the massive rapid rotator V986 Oph

Handler

Shobbrook

Uytterhoeven³

et al. 2012

Monthly Notices of the Royal Astronomical Society

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“…Indeed, the field strength observed in this star is higher than the critical field limit needed to inhibit mixing that was determined from theory (see Zahn 2011;Neiner et al 2012a). A recent study of the B3IV single star HD 43317 revealed it to be a promising target to explore the effects of magnetism on stellar interiors of main-sequence B-type stars in more detail.…”

Section: Introductionmentioning

confidence: 82%

Discovery of a magnetic field in the CoRoT hybrid B-type pulsator HD 43317

Briquet

Neiner

Leroy

et al. 2013

A&A

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Context. A promising way of testing the impact of a magnetic field on internal mixing (core overshooting, internal rotation) in mainsequence B-type stars is to perform asteroseismic studies of a sample of magnetic pulsators. Aims. The CoRoT satellite revealed that the B3IV star HD 43317 is a hybrid SPB/β Cep-type pulsator that has a wealth of pulsational constraints on which one can perform a seismic modelling, in particular, probing the extent of its convective core and mixing processes. Moreover, indirect indicators of a magnetic field in the star were observed: rotational modulation due to chemical or temperature spots and X-ray emission. Our goal was to directly investigate the field in HD 43317 and, if it is magnetic, to characterise it. Methods. We collected data with the Narval spectropolarimeter installed at Télescope Bernard Lyot (TBL, Pic du Midi, France) and applied the least-squares deconvolution technique to measure the circular polarisation of the light emitted from HD 43317. We modelled the longitudinal field measurements directly with a dipole. Results. Zeeman signatures in the Stokes V profiles of HD 43317 are clearly detected and rotationally modulated, which proves that this star exhibits an oblique magnetic field. The modulation with the rotation period deduced from the CoRoT light curve is also confirmed, and we found a field strength at the poles of about 1 kG. Our result must be taken into account in future seismic modelling work of this star.

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“…Moreover, there are only a few detailed studies of the magnetic field configuration for these objects (e.g. Hubrig et al 2011;Henrichs et al 2012;Neiner et al 2012a). …”

Section: Introductionmentioning

confidence: 99%

Weak magnetic field, solid-envelope rotation, and wave-induced N-enrichment in the SPB starζCassiopeiae

Briquet¹,

Neiner²,

Petit³

et al. 2016

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Aims. The main-sequence B-type star ζ Cassiopeiae is known as a N-rich star with a magnetic field discovered with the Musicos spectropolarimeter. We model the magnetic field of the star by means of 82 new spectropolarimetric observations of higher precision to investigate the field strength, topology, and effect. Methods. We gathered data with the Narval spectropolarimeter installed at Télescope Bernard Lyot (TBL; Pic du Midi, France) and applied the least-squares deconvolution technique to measure the circular polarisation of the light emitted from ζ Cas. We used a dipole oblique rotator model to determine the field configuration by fitting the longitudinal field measurements and by synthesizing the measured Stokes V profiles. We also made use of the Zeeman-Doppler imaging technique to map the stellar surface and to deduce the difference in rotation rate between the pole and equator. Results. ζ Cas exhibits a polar field strength B pol of 100−150 G, which is the weakest polar field observed so far in a massive mainsequence star. Surface differential rotation is ruled out by our observations and the field of ζ Cas is strong enough to enforce rigid internal rotation in the radiative zone according to theory. Thus, the star rotates as a solid body in the envelope. Conclusions. We therefore exclude rotationally induced mixing as the cause of the surface N-enrichment. We discuss that the transport of chemicals from the core to the surface by internal gravity waves is the most plausible explanation for the nitrogen overabundance at the surface of ζ Cas.

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Detecting and modelling the magnetic field of theβ Cephei star V 2052 Ophiuchi

Cited by 42 publications

References 20 publications

A multisite photometric study of two unusual β Cep stars: the magnetic V2052 Oph and the massive rapid rotator V986 Oph

A multisite photometric study of two unusual β Cep stars: the magnetic V2052 Oph and the massive rapid rotator V986 Oph

Discovery of a magnetic field in the CoRoT hybrid B-type pulsator HD 43317

Weak magnetic field, solid-envelope rotation, and wave-induced N-enrichment in the SPB starζCassiopeiae

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