Can Magnetic Fields Be Detected in Be Stars?

Mathys, G.; Smith, M. A.

doi:10.1017/s0252921100056062

Cited by 3 publications

(5 citation statements)

References 8 publications

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“…In this way we get information on the behaviour of the localized transient magnetic field over at least a part of the stellar surface. A similar study was conducted for the Be star λ Eri in the past by Mathys & Smith (2000) with CASPEC at the ESO 3.6 m telescope, where some constraints on a possible presence of a magnetic field were discussed.…”

Section: Observations and Data Reductionmentioning

confidence: 90%

Magnetic survey of emission line B‐type stars with FORS 1 at the VLT

Hubrig¹,

Schöller

Саванов

et al. 2009

Astron Nachr

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We report the results of our search for magnetic fields in a sample of 16 field Be stars, the binary emission-line B-type star υ Sgr, and in a sample of fourteen members of the open young cluster NGC 3766 in the Carina spiral arm. The sample of cluster members includes Be stars, normal B-type stars and He-strong/He-weak stars. Nine Be stars have been studied with magnetic field time series obtained over ∼1 hour to get an insight into the temporal behaviour and the correlation of magnetic field properties with dynamical phenomena taking place in Be star atmospheres. The spectropolarimetric data were obtained at the European Southern Observatory with the multi-mode instrument FORS 1 installed at the 8 m Kueyen telescope. We detect weak photospheric magnetic fields in four field Be stars, HD 62367, μ Cen, o Aqr, and Tuc. The strongest longitudinal magnetic field, Bz = 117±38 G, was detected in the Be star HD 62367. Among the Be stars studied with time series, one Be star, λ Eri, displays cyclic variability of the magnetic field with a period of 21.12 min. The binary star υ Sgr, in the initial rapid phase of mass exchange between the two components with strong emission lines in the visible spectrum, is a magnetic variable star, probably on a timescale of a few months. The maximum longitudinal magnetic field Bz = −102±10 G at MJD 54333.018 was measured using hydrogen lines. The cluster NGC 3766 seems to be extremely interesting, where we find evidence for the presence of a magnetic field in seven early B-type stars out of the observed fourteen cluster members.

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Section: Observations and Data Reductionmentioning

confidence: 90%

Magnetic survey of emission line B‐type stars with FORS 1 at the VLT

Hubrig¹,

Schöller

Саванов

et al. 2009

Astron Nachr

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“…The need of such observations is real, however, since a strong debate is still ongoing regarding the existence and influence of magnetic fields in hot-star winds. The only serious attempt on a broadline star has been carried out by Mathys & Smith (2000) for the active B3 Ve star l Eri ( km s ) using the Ϫ1 v sin i ∼ 310 same CASPEC spectropolarimeter. However, the attained S/N per pixel at for the combined data was at best 450 R p 30,000 because of weather restrictions.…”

Section: Discussionmentioning

confidence: 99%

“…The best direct method of searching for polarization signal consists of normalizing the continuum locally around each line of interest, as was done by Mathys & Smith (2000) for the He i l6678 line of l Eri with the same instrument. This timeconsuming method limits the number of useful lines considerably, since the position of the line in the order critically determines the quality of the fit.…”

Section: Normalizationmentioning

confidence: 99%

“…From the two variability studies in Stokes I and V, we can theoretically provide some constraints on any localized, transient magnetic field in z Puppis following a technique already used by Mathys & Smith (2000). To derive these constraints, we assume a localized magnetic plasma within a small region on the stellar surface, which creates a narrow signature in DI a line of a light element as seen in hot-star spectra (He, C, …) resulting from a density/temperature contrast.…”

Section: Constraints On Localized Magnetic Fieldsmentioning

confidence: 99%

“…To derive these constraints, we assume a localized magnetic plasma within a small region on the stellar surface, which creates a narrow signature in DI a line of a light element as seen in hot-star spectra (He, C, …) resulting from a density/temperature contrast. Under the weakfield approximation, which implies that the separation between the magnetic line components j and p is small with respect to the intrinsic width of the emergent line without magnetic field, the perturbation can be related to the Stokes V perturbation DI (Mathys & Smith 2000):…”

Section: Constraints On Localized Magnetic Fieldsmentioning

confidence: 99%

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Detecting Magnetic Fields in Rotationally Perturbed, Hot Stellar Winds

Chesneau¹,

Moffat²

2002

PUBL ASTRON SOC PAC

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ABSTRACT. In this paper, we report on an attempt to optically detect localized and/or variable magnetic fields in the single O4 I(n)f star z Puppis and in the WC 8 star in the binary star g 2 Velorum with the spectropolarimeter Cassegrain echelle spectrograph mounted on the ESO 3.6 m telescope. The spectra cover 5700-6800 Å with resolution element 0.2 Å . These stars are sufficiently bright in principle to obtain Stokes V spectra with excellent signal-to-noise ratio and temporal resolution at this telescope. We discuss several procedures adapted to the extraction of the polarized signal from broad lines to put constraints on the global and local magnetic fields. Despite some instrumental difficulties, we report a null longitudinal component of the global magnetic field measurement in z Pup with G. We also find no significant activity in Stokes V above in10 minutes in z Puppis's observable photospheric lines, in a spectral bandpass of 0.2-3 Å . We also report a null detection above for the emission lines of g Vel. Spectral variability in natural light for these stars is 3j ∼ 0.3% V also discussed. Finally, we discuss the potential of such spectropolarimetric techniques in the context of newgeneration spectropolarimeters.

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Evidence for weak magnetic fields in early‐type emission stars

Hubrig¹,

Yudin

Погодин

et al. 2007

Astron Nachr

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We report the results of our study of magnetic fields in a sample of 15 Be stars using spectropolarimetric data obtained at the European Southern Observatory with the multi-mode instrument FORS1 installed at the 8m Kueyen telescope. We detect weak photospheric magnetic fields in four stars, HD56014, HD148184, HD155806, and HD181615. We note that for HD181615 the evolutionary status is not obvious due to the fact that it is a binary system currently observed in the initial rapid phase of mass exchange between the two components. Further, we notify the possible presence of distinct circular polarisation features in the circumstellar components of Ca II H&K in three stars, HD58011, HD117357, and HD181615, hinting at a probable presence of magnetic fields in the circumstellar mass loss disks of these stars. We emphasize the need for future spectropolarimetric observations of Be stars with detected magnetic fields to study the temporal evolution of their magnetic fields and the correlation of magnetic field properties with dynamical phenomena taking place in the gaseous circumstellar disks of these stars.Comment: 4 pages, 3 figures, 1 table, accepted for publication in A

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Can Magnetic Fields Be Detected in Be Stars?

Cited by 3 publications

References 8 publications

Magnetic survey of emission line B‐type stars with FORS 1 at the VLT

Magnetic survey of emission line B‐type stars with FORS 1 at the VLT

Detecting Magnetic Fields in Rotationally Perturbed, Hot Stellar Winds

Evidence for weak magnetic fields in early‐type emission stars

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