Accurate magnetic field measurements of Vega-like stars  and Herbig Ae/Be stars

Hubrig, S.; Yudin, R. V.; Schöller, M.; Погодин, М. А.

doi:10.1051/0004-6361:20053794

Cited by 72 publications

(93 citation statements)

References 41 publications

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“…A second detection in HD 139614 ( B z = −116 ± 34 G) was claimed by Hubrig et al (2006c), who also confirmed their previous measurement of −450 G. Later, Hubrig et al (2007a) revised both FORS1 observations, and reported B z − 112 ± 36 G and B z = −93 ± 14 G, for the first and the second measurement, respectively. A magnetic field was not detected in a third FORS1 measurement reported by Hubrig et al (2009c).…”

Section: Herbig Aebe Starssupporting

confidence: 61%

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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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Section: Herbig Aebe Starssupporting

confidence: 61%

“…Further surveys of Herbig AeBe stars using FORS1 were described by Hubrig et al (2006c) and Hubrig et al (2007a). Altogether, these papers reported the discovery of a magnetic field in three Herbig stars: HD 31648, HD 144432, and HD 144668.…”

Section: Herbig Aebe Starsmentioning

confidence: 96%

Magnetic field measurements and their uncertainties: the FORS1 legacy

Bagnulo

Landstreet

Fossati

et al. 2012

A&A

147

278

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“…The results of the spectropolarimetric observations of the two Herbig Ae stars HD 31648 and HD 190073 with FORS 1 at a resolution of R ≈ 4000 turned out to be especially remarkable (Hubrig et al 2006a;Hubrig et al 2007a). These two stars possess almost the same effective temperature, but are different in luminosity and projected rotation velocity.…”

Section: Introductionmentioning

confidence: 96%

Searching for a link between the magnetic nature and other observed properties of Herbig Ae/Be stars and stars with debris disks

Hubrig

Stelzer

Schöller

et al. 2009

A&A

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100

149

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Context. Recently, evidence for the presence of weak magnetic fields in Herbig Ae/Be stars has been found in several studies. Aims. We seek to expand the sample of intermediate-mass pre-main sequence stars with circular polarization data to measure their magnetic fields, and to determine whether magnetic field properties in these stars are correlated with mass-accretion rate, disk inclination, companions, silicates, PAHs, or show a correlation with age and X-ray emission as expected for the decay of a remnant dynamo. Methods. Spectropolarimetric observations of 21 Herbig Ae/Be stars and six debris disk stars have been obtained at the European Southern Observatory with FORS 1 mounted on the 8 m Kueyen telescope of the VLT. With the GRISM 600B in the wavelength range 3250-6215 Å we were able to cover all hydrogen Balmer lines from Hβ to the Balmer jump. In all observations a slit width of 0. 4 was used to obtain a spectral resolving power of R ≈ 2000. Results. Among the 21 Herbig Ae/Be stars studied, new detections of a magnetic field were achieved in six stars. For three Herbig Ae/Be stars, we confirm previous magnetic field detections. The largest longitudinal magnetic field, B z = −454 ± 42 G, was detected in the Herbig Ae/Be star HD 101412 using hydrogen lines. No field detection at a significance level of 3σ was achieved in stars with debris disks. Our study does not indicate any correlation of the strength of the longitudinal magnetic field with disk orientation, disk geometry, or the presence of a companion. We also do not see any simple dependence on the mass-accretion rate. However, it is likely that the range of observed field values qualitatively supports the expectations from magnetospheric accretion models giving support for dipole-like field geometries. Both the magnetic field strength and the X-ray emission show hints of a decline with age in the range of ∼2-14 Myr probed by our sample, supporting a dynamo mechanism that decays with age. However, our study of rotation does not show any obvious trend of the strength of the longitudinal magnetic field with rotation period. Furthermore, the stars seem to obey the universal power-law relation between magnetic flux and X-ray luminosity established for the Sun and main-sequence active dwarf stars.

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“…6 and following). Hubrig et al (2006Hubrig et al ( , 2009) reported a longitudinal magnetic field of 84±30 Gauss, up to 104±19 Gauss, while CAT found a longitudinal field of 74±10 Gauss.…”

Section: Introductionmentioning

confidence: 97%

The absorption and emission spectrum of the magnetic Herbig Ae star HD 190073

Cowley¹,

Hubrig²

2012

Astron Nachr

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We determine abundances from the absorption spectrum of the magnetic Herbig Ae star HD 190073 (V1295 Aql). The observations are primarily from HARPS spectra obtained at a single epoch. We accept arguments that the presence of numerous emission lines does not vitiate a classical abundance analysis, though it likely reduces the achievable accuracy. Most abundances are closely solar, but several elements show departures of a factor of two to three, as an earlier study has also shown. We present quantitative measurements of more than 60 emission lines, peak intensities, equivalent widths, and FWHM's. The latter range from over 200 km s −1 (Hα, He D3) down to 10-20 km s −1 (forbidden lines

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Accurate magnetic field measurements of Vega-like stars and Herbig Ae/Be stars

Cited by 72 publications

References 41 publications

Magnetic field measurements and their uncertainties: the FORS1 legacy

Magnetic field measurements and their uncertainties: the FORS1 legacy

Searching for a link between the magnetic nature and other observed properties of Herbig Ae/Be stars and stars with debris disks

The absorption and emission spectrum of the magnetic Herbig Ae star HD 190073

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