New magnetic field measurements of <i>β</i> Cephei stars and slowly pulsating B stars

Hubrig, S.; Briquet, Maryline; Cat, P. De; Schoeller, Markus; Morel, Thierry; Ilyin, I.

doi:10.1002/asna.200811187

Cited by 70 publications

(98 citation statements)

References 35 publications

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“…Improved agreement between observation and theory may be achieved when tailored abundances are used for the stellar evolution models, see also the previous footnote. 4 A magnetic field is present also in HD 74575 (Hubrig et al 2009). ( Fig.…”

Section: Observational Constraintsmentioning

confidence: 91%

Mixing of CNO-cycled matter in massive stars

Przybilla¹,

Firnstein²,

Nieva

et al. 2010

A&A

139

150

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Aims. We test predictions of evolution models on mixing of CNO-cycled products in massive stars from a fundamental perspective. Relative changes within the theoretical C:N:O abundance ratios and the buildup of helium are compared with observational results. Methods. A sample of well-studied Galactic massive stars is presented. High-quality optical spectra are carefully analysed using improved NLTE line-formation and comprehensive analysis strategies. The results are put in the context of the existing literature data. Results. A tight trend in the observed N/C vs. N/O ratios and the buildup of helium is found from the self-consistent analysis of main-sequence to supergiant stars for the first time. The catalytic nature of the CNO-cycles is confirmed quantitatively, though further investigations are required to derive a fully consistent picture. Our observational results support the case of strong mixing, as predicted e.g. by evolution models that consider magnetic fields or by models that have gone through the first dredge-up in the case of many supergiants.

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Section: Observational Constraintsmentioning

confidence: 91%

Mixing of CNO-cycled matter in massive stars

Przybilla¹,

Firnstein²,

Nieva

et al. 2010

A&A

139

150

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“…In particular, the six reported detections of a field in HD 16582 all have decreased below the 3σ significance limit, although one measurement not originally claimed as detection by Hubrig et al (2009a), on MJD = 54 343.259, has risen to the apparently significant value of −104 ± 19 G. A single ESPaDOnS field measurement detects no trace of a field with B z uncertainty of 10 G (Silvester et al 2009). While it is still possible that a field might be present in HD 16582, this must certainly be regarded at present as -at best -extremely uncertain.…”

Section: β Cephei Pulsators and Slowly Pulsating B Starsmentioning

confidence: 99%

“…If these results were confirmed, they would be quite important; such high incidence of detected fields would strongly suggest that magnetism is intrinsically connected with the pulsation phenomenon in early B-type stars, as it is in the cool rapidly oscillating Ap (roAp) stars. Hubrig et al (2006a) and Hubrig et al (2009a) have reported discovery of a field in the β Cep star ξ 1 CMa = HD 46328, based on altogether 13 detections at approximately the 6 or 7σ level.…”

Section: β Cephei Pulsators and Slowly Pulsating B Starsmentioning

confidence: 99%

Magnetic field measurements and their uncertainties: the FORS1 legacy

Bagnulo

Landstreet

Fossati

et al. 2012

A&A

149

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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“…Finally, we point out that Hubrig et al (2011) obtained and analysed spectropolarimetric time series observations taken with the SOFIN échelle spectrograph at the 2.56 m Nordic Optical Telescope, after the discovery of a magnetic field in the star (Hubrig et al 2009). From their 13 data points, three dominant peaks emerged in the periodogram, with the highest peak at 0.072 d −1 .…”

Section: Summary Of Observational Constraintsmentioning

confidence: 99%

Seismic modelling of theβ Cephei star HD 180642 (V1449 Aquilae)

Aerts

Briquet

Degroote

et al. 2011

A&A

Self Cite

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Context. We present modelling of the β Cep star HD 180642 based on its observational properties deduced from CoRoT and groundbased photometry as well as from time-resolved spectroscopy. Aims. We investigate whether present-day state-of-the-art models are able to explain the full seismic behaviour of this star, which has extended observational constraints for this type of pulsator. Methods. We constructed a dedicated database of stellar models and their oscillation modes tuned to fit the dominant radial mode frequency of HD 180642, by means of varying the hydrogen content, metallicity, mass, age, and core overshooting parameter. We compared the seismic properties of these models with those observed. Results. We find models that are able to explain the numerous observed oscillation properties of the star, for a narrow range in mass of 11.4-11.8 M and no or very mild overshooting (with up to 0.05 local pressure scale heights), except for an excitation problem of the = 3, p 1 mode. We deduce a rotation period of about 13 d, which is fully compatible with recent magnetic field measurements. The seismic models do not support the earlier claim of solar-like oscillations in the star. We instead ascribe the power excess at high frequency to non-linear resonant mode coupling between the high-amplitude radial fundamental mode and several of the low-order pressure modes. We report a discrepancy between the seismic and spectroscopic gravity at the 2.5σ level.

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

Cited by 70 publications

References 35 publications

Mixing of CNO-cycled matter in massive stars

Mixing of CNO-cycled matter in massive stars

Magnetic field measurements and their uncertainties: the FORS1 legacy

Seismic modelling of theβ Cephei star HD 180642 (V1449 Aquilae)

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