CRITICAL EVALUATION OF MAGNETIC FIELD DETECTIONS REPORTED FOR PULSATING B-TYPE STARS IN LIGHT OF ESPaDOnS, NARVAL, AND REANALYZED FORS1/2 OBSERVATIONS

Shultz, Matthew; Wade, G. A.; Grunhut, J.; Bagnulo, S.; Landstreet, J. D.; Neiner, C.; Alécian, E.; Hanes, David A.

doi:10.1088/0004-637x/750/1/2

Cited by 37 publications

(37 citation statements)

References 34 publications

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“…The first reliable detection was confirmed with ESPaDOnS data by Shultz et al (2012). Here we report for the first time the detection of a magnetic field in both components of ǫ Lupi, making it the first known close binary with two magnetic, massive stars.…”

Section: Introductionsupporting

confidence: 57%

Detection of magnetic fields in both B-type components of the ϵ Lupi system: a new constraint on the origin of fossil fields?

Shultz

Wade

Alécian

et al. 2015

Monthly Notices of the Royal Astronomical Society: Letters

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High-resolution circular spectropolarimetric observations, obtained with ESPaDOnS in the context of the BinaMIcS Large Program, have revealed a magnetic field in the B3V secondary component of the SB2 binary system ǫ Lupi (B2/B3). As the B2V primary is already known to be magnetic, this is the first detection of a magnetic field in both components of an early-type binary system. The longitudinal magnetic field of the primary is ∼ −200 G; that of the secondary ∼ +100 G. Observations can be approximately reproduced by a model assuming the magnetic axes of the two stars are anti-aligned, and roughly parallel to their respective rotation axes. Estimated magnetospheric radii indicate a high probability that their magnetospheres are interacting. As many of the arguments for the different proposed formation scenarios of fossil magnetic fields rely upon evidence drawn from investigations of close binaries, in particular the rarity of magnetic ABO stars in close binaries and the previous absence of any known close binary with two magnetic, massive stars, this discovery may be an important new constraint on the origin of fossil magnetic fields.

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Section: Introductionsupporting

confidence: 57%

Detection of magnetic fields in both B-type components of the ϵ Lupi system: a new constraint on the origin of fossil fields?

Shultz

Wade

Alécian

et al. 2015

Monthly Notices of the Royal Astronomical Society: Letters

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“…The star HD 46328 (ξ 1 CMa) is a β Cep star (Saesen et al 2006) for which the presence of a magnetic field has first been reported by Hubrig et al (2006Hubrig et al ( , 2009. This was further confirmed by high-resolution spectropolarimetry (Silvester et al 2009;Fourtune-Ravard et al 2011;Shultz et al 2012). Hubrig et al (2011) used the FORS1 measurements to model the magnetic field of HD 46328, assuming a dipolar configuration of the magnetic field.…”

Section: Magnetic Field Detection Ratementioning

confidence: 83%

B fields in OB stars (BOB): Low-resolution FORS2 spectropolarimetry of the first sample of 50 massive stars

Fossati

Castro

Schöller

et al. 2015

A&A

110

111

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Within the context of the collaboration "B fields in OB stars" (BOB), we used the FORS2 low-resolution spectropolarimeter to search for a magnetic field in 50 massive stars, including two reference magnetic massive stars. Because of the many controversies of magnetic field detections obtained with the FORS instruments, we derived the magnetic field values with two completely independent reduction and analysis pipelines. We compare and discuss the results obtained from the two pipelines. We obtained a general good agreement, indicating that most of the discrepancies on magnetic field detections reported in the literature are caused by the interpretation of the significance of the results (i.e., 3-4σ detections considered as genuine, or not), instead of by significant differences in the derived magnetic field values. By combining our results with past FORS1 measurements of HD 46328, we improve the estimate of the stellar rotation period, obtaining P = 2.17950 ± 0.00009 days. For HD 125823, our FORS2 measurements do not fit the available magnetic field model, based on magnetic field values obtained 30 years ago. We repeatedly detect a magnetic field for the O9.7V star HD 54879, the HD 164492C massive binary, and the He-rich star CPD −57 3509. We obtain a magnetic field detection rate of 6 ± 4%, while by considering only the apparently slow rotators we derive a detection rate of 8 ± 5%, both comparable with what was previously reported by other similar surveys. We are left with the intriguing result that, although the large majority of magnetic massive stars is rotating slowly, our detection rate is not a strong function of the stellar rotational velocity.

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“…The LSD profiles are therefore sensitive even to the field topologies that yield very low or null mean longitudinal fields (e.g. Shultz et al 2012). The LSD method has been successfully used to detect and map complex dynamo-generated magnetic fields of cool active stars (Donati et al 2003;Kochukhov et al 2013).…”

Section: Methodsmentioning

confidence: 99%

Detectability of small-scale magnetic fields in early-type stars

Kochukhov

Sudnik

2013

A&A

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Context. Strong, globally-organized magnetic fields are found for a small fraction of O, B, and A stars. At the same time, many theoretical and indirect observational studies have suggested the ubiquitous presence of weak localized magnetic fields at the surfaces of massive stars. However, no direct detections of such fields have been reported yet. Aims. We have carried out the first comprehensive theoretical investigation of the spectropolarimetric observational signatures of the structured magnetic fields. These calculations are applied to interpret null results of the recent magnetic surveys of massive stars. Methods. The intensity and circular polarization spectra of early-type stars were simulated using detailed polarized radiative transfer calculations with LTE model atmospheres. Similar to observational analyses, the mean Stokes I and V line profiles were obtained by applying a multiline averaging technique. Different spectropolarimetric observables were examined for multiple realizations of randomly distributed radial magnetic field spots on different spatial scales. Results. We characterize the amplitude of the circular polarization profiles and the mean longitudinal magnetic field as a function of magnetic spot sizes. The dependence of these observables on the effective temperature, projected rotational velocity, and inclination angle is also investigated. Using results of the recently completed Magnetism in Massive Stars (MiMeS) survey, we derive upper limits on the small-scale magnetic fields compatible with the MiMeS nondetections. Conclusions. According to our simulations, existing spectropolarimetric observations of sharp-lined massive stars rule out the presence of any small-scale fields stronger than 50-250 G, depending on the typical spot sizes. For broad-lined stars, the observations constrain such fields to being below approximately 1 kG.

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CRITICAL EVALUATION OF MAGNETIC FIELD DETECTIONS REPORTED FOR PULSATING B-TYPE STARS IN LIGHT OF ESPaDOnS, NARVAL, AND REANALYZED FORS1/2 OBSERVATIONS

Cited by 37 publications

References 34 publications

Detection of magnetic fields in both B-type components of the ϵ Lupi system: a new constraint on the origin of fossil fields?

Detection of magnetic fields in both B-type components of the ϵ Lupi system: a new constraint on the origin of fossil fields?

B fields in OB stars (BOB): Low-resolution FORS2 spectropolarimetry of the first sample of 50 massive stars

Detectability of small-scale magnetic fields in early-type stars

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