Rotation, pulsations and magnetic field in V 2052 Ophiuchi: A new He-strong star

Neiner, C.; Henrichs, H.F.; Floquet, M.; Frémat, Y.; Preuss, O.; Hubert, A. M.; Geers, V. C.; Tijani, A.; Nichols, Joy S.; Jankov, S.

doi:10.1051/0004-6361:20031342

Cited by 74 publications

(96 citation statements)

References 37 publications

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“…For all these stars we have magnetic field detections. In addition, two other β Cephei stars, V2052 Oph and β Cep, of their sample with detected longitudinal magnetic fields of the order of ∼100 G (Neiner et al 2003b;Henrichs et al 2000) were found to show nitrogen enhancement. For the sixth β Cephei star with a detected magnetic field, HD 180642, Morel & Aerts (2007) found a mild nitrogen overabundance, though boron data are not available.…”

Section: Resultsmentioning

confidence: 94%

“…The first detection of a weak magnetic field in the SPB star ζ Cas was reported by Neiner et al (2003b). In our first publication on the magnetic survey of pulsating B-type stars (Hubrig et al 2006), we announced detections of weak mean longitudinal magnetic fields of the order of a few hundred Gauss in 13 SPB stars and in the β Cephei star ξ 1 CMa.…”

Section: Introductionmentioning

confidence: 95%

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New magnetic field measurements of β Cephei stars and slowly pulsating B stars

Hubrig¹,

Briquet²,

Cat³

et al. 2009

Astron Nachr

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We present the results of the continuation of our magnetic survey with FORS 1 at the VLT of a sample of B-type stars consisting of confirmed or candidate β Cephei stars and Slowly Pulsating B (hereafter SPB) stars, along with a small number of normal B-type stars. A weak mean longitudinal magnetic field of the order of a few hundred Gauss was detected in three β Cephei stars and two stars suspected to be β Cephei stars, in five SPB stars and eight stars suspected to be SPB stars. Additionally, a longitudinal magnetic field at a level larger than 3σ has been diagnosed in two normal B-type stars, the nitrogen-rich early B-type star HD 52089 and in the B5 IV star HD 153716. Roughly one third of β Cephei stars have detected magnetic fields: Out of 13 β Cephei stars studied to date with FORS 1, four stars possess weak magnetic fields, and out of the sample of six suspected β Cephei stars two show a weak magnetic field. The fraction of magnetic SPBs and candidate SPBs is found to be higher: Roughly half of the 34 SPB stars have been found to be magnetic and among the 16 candidate SPBs eight stars possess magnetic fields. In an attempt to understand why only a fraction of pulsating stars exhibit magnetic fields, we studied the position of magnetic and non-magnetic pulsating stars in the H-R diagram. We find that their domains in the H-R diagram largely overlap, and no clear picture emerges as to the possible evolution of the magnetic field across the main sequence. It is possible that stronger fields tend to be found in stars with lower pulsating frequencies and smaller pulsating amplitudes. A somewhat similar trend is found if we consider a correlation between the field strength and the v sin i-values, i.e. stronger magnetic fields tend to be found in more slowly rotating stars.

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Section: Resultsmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 95%

New magnetic field measurements of β Cephei stars and slowly pulsating B stars

Hubrig¹,

Briquet²,

Cat³

et al. 2009

Astron Nachr

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“…A magnetic field was reported in the β Cep star V2052 Oph = HD 163472 by Neiner et al (2003b), again based on MuSiCoS observations. The measurements presented appear to support the claimed discovery, but are very close to the limit of detection.…”

Section: β Cephei Pulsators and Slowly Pulsating B Starsmentioning

confidence: 80%

Magnetic field measurements and their uncertainties: the FORS1 legacy

Bagnulo

Landstreet

Fossati

et al. 2012

A&A

147

278

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Context. During the last decade, the FORS1 instrument of the ESO Very Large Telescope has been extensively used to study stellar magnetism. A number of interesting discoveries of magnetic fields in several classes of stars have been announced, many of which obtained at a ∼3σ level; some of the discoveries are confirmed by measurements obtained with other instruments, some are not. Aims. We investigate the reasons for the discrepancies between the results obtained with FORS1 and those obtained with other instruments. Methods. Using the ESO FORS pipeline, we have developed a semi-automatic procedure for magnetic field determination. We have applied this procedure to the full content of circular spectropolarimetric measurements of the FORS1 archive (except for most of the observations obtained in multi-object spectropolarimetric mode). We have devised and applied a number of consistency checks to our field determinations, and we have compared our results to those previously published in the literature. Results. We find that for high signal-to-noise ratio measurements, photon noise does not account for the full error bars. We discuss how field measurements depend on the specific algorithm adopted for data reduction, and we show that very small instrument flexures, negligible in most of the instrument applications, may be responsible for some spurious field detections in the null profiles. Finally, we find that we are unable to reproduce some results previously published in the literature. Consequently, we do not confirm some important discoveries of magnetic fields obtained with FORS1 and reported in previous publications. Conclusions. Our revised field measurements show that there is no contradiction between the results obtained with the low-resolution spectropolarimeter FORS1 and those obtained with high-resolution spectropolarimeters. FORS1 is an instrument capable of performing reliable magnetic field measurements, provided that the various sources of uncertainties are properly taken into account.

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“…A preliminary analysis of the star indicated inconsistencies of the solution, which were unexpected in view of the "normal" appearance implied by the analysis of Morel et al (2006). However, a detailed study by Neiner et al (2003) found HD 163472 to be chemically peculiar, in particular it is a He-strong star. Diffusion in the magnetic atmosphere renders this otherwise highly interesting star useless for our purpose.…”

Section: Stars Excluded From the Analysismentioning

confidence: 94%

“…Systematic effects on the abundance analysis due to the presence of magnetic fields are also not expected. Only three sample stars have a confirmed magnetic field, β Cep (Henrichs et al 2000), ζ Cas (Neiner et al 2003) and τ Sco (Donati et al 2006). To date, none of these shows observational evidence for abundance spots or vertical chemical stratification.…”

Section: Chemical Abundancesmentioning

confidence: 95%

Present-day cosmic abundances

Nieva

Przybilla²

2012

A&A

431

517

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Context. Early B-type stars are ideal indicators for present-day cosmic abundances since they preserve their pristine abundances and typically do not migrate far beyond their birth environments over their short lifetimes, in contrast to older stars like the Sun. They are also unaffected by depletion onto dust grains, unlike the cold/warm interstellar medium (ISM) or H ii regions. Aims. A carefully selected sample of early B-type stars in OB associations and the field within the solar neighbourhood is studied comprehensively. Quantitative spectroscopy is used to characterise their atmospheric properties in a self-consistent way. Present-day abundances for the astrophysically most interesting chemical elements are derived in order to investigate whether a present-day cosmic abundance standard can be established. Methods. High-resolution and high-S/N FOCES, FEROS and ELODIE spectra of well-studied sharp-lined early B-type stars are analysed in non-LTE. Line-profile fits based on extensive model grids and an iterative analysis methodology are used to constrain stellar parameters and elemental abundances at high accuracy and precision. Atmospheric parameters are derived from the simultaneous establishment of independent indicators, from multiple ionization equilibria and the Stark-broadened hydrogen Balmer lines, and they are confirmed by reproduction of the stars' global spectral energy distributions. Results. Effective temperatures are constrained to 1-2% and surface gravities to less than 15% uncertainty, along with accurate rotational, micro-and macroturbulence velocities. Good agreement of the resulting spectroscopic parallaxes with those from the new reduction of the Hipparcos catalogue is obtained. Absolute values for abundances of He, C, N, O, Ne, Mg, Si and Fe are determined to better than 25% uncertainty. The synthetic spectra match the observations reliably over almost the entire visual spectral range. Three sample stars, γ Ori, o Per and θ 1 Ori D, are identified as double-lined, indicating the presence of an early/mid B-type companion. Conclusions. A present-day cosmic abundance standard is established from a sample of 29 early B-type stars, indicating abundance fluctuations of less than 10% around the mean. Our results (i) resolve the long-standing discrepancy between a chemical homogeneous gas-phase ISM and a chemically inhomogeneous young stellar component out to several hundred parsec from the Sun, (ii) facilitate the amount of heavy elements locked up in the interstellar dust to be constrained precisely -the results imply that carbonaceous dust is largely destroyed inside the Orion H ii region, unlike the silicates, and that graphite is only a minority species in interstellar dust -, (iii) show that the mixing of CNO-burning products in the course of massive star evolution follows tightly the predicted nuclear path, (iv) provide reliable present-day reference points for anchoring Galactic chemical evolution models to observation, and (v) imply that the Sun has migrated outwards from the inne...

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Rotation, pulsations and magnetic field in V 2052 Ophiuchi: A new He-strong star

Cited by 74 publications

References 37 publications

New magnetic field measurements of β Cephei stars and slowly pulsating B stars

New magnetic field measurements of β Cephei stars and slowly pulsating B stars

Magnetic field measurements and their uncertainties: the FORS1 legacy

Present-day cosmic abundances

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