The Rigidly Rotating Magnetosphere of σ Orionis E

Townsend, R. H. D.; Owocki, S. P.; Groote, D.

doi:10.1086/462413

Cited by 129 publications

(126 citation statements)

References 21 publications

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“…The model provides a good match to the data whenever detailed observations are available Gagné et al 2005). MHD numerical simulations have been carried out for various cases, confirming and extending the predictions of the earlier models (ud-Doula & Owocki 2002;Owocki & ud-Doula 2004;Townsend et al 2005;ud-Doula et al 2006;Townsend et al 2007;Ud-Doula et al 2008). In particular, these computations are able to reproduce the anomalously high and hard X-ray emission of magnetic massive stars.…”

Section: Diffusion Mass-loss and Evolutionsupporting

confidence: 73%

Magnetic Fields of Nondegenerate Stars

Donati

Landstreet

2009

Annu. Rev. Astron. Astrophys.

660

656

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Magnetic fields are present in a wide variety of stars throughout the HR diagram and play a role at basically all evolutionary stages, from very-low-mass dwarfs to very massive stars, and from young star-forming molecular clouds and protostellar accretion discs to evolved giants/supergiants and magnetic white dwarfs/neutron stars. These fields range from a few µ G (e.g., in molecular clouds) to TG and more (e.g., in magnetic neutron stars); in non-degenerate stars in particular, they feature large-scale topologies varying from simple nearly-axisymmetric dipoles to complex non-axsymmetric structures, and from mainly poloidal to mainly toroidal topology.After recalling the main techniques of detecting and modelling stellar magnetic fields, we review the existing properties of magnetic fields reported in cool, hot and young non-degenerate stars and protostars, and discuss our understanding of the origin of these fields and their impact on the birth and life of stars.

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Section: Diffusion Mass-loss and Evolutionsupporting

confidence: 73%

Magnetic Fields of Nondegenerate Stars

Donati

Landstreet

2009

Annu. Rev. Astron. Astrophys.

660

656

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“…Townsend et al 2005). As a result, depending on the angle between the rotation and magnetic axis and on the geometry of the magnetic field, circumstellar clouds or discs are forming that rotate rigidly with the star.…”

Section: Hα Magnetospheric Signaturesmentioning

confidence: 99%

Discovery of new magnetic early-B stars within the MiMeS HARPSpol survey

Alécian

Kochukhov

Petit

et al. 2014

A&A

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Context. The Magnetism in Massive Stars (MiMeS) project aims at understanding the origin of the magnetic fields in massive stars as well as their impact on stellar internal structure, evolution, and circumstellar environment. Aims. One of the objectives of the MiMeS project is to provide stringent observational constraints on the magnetic fields of massive stars; however, identification of magnetic massive stars is challenging, as only a few percent of high-mass stars host strong fields detectable with the current instrumentation. Hence, one of the first objectives of the MiMeS project was to search for magnetic objects among a large sample of massive stars, and to build a sub-sample for in-depth follow-up studies required to test the models and theories of fossil field origins, magnetic wind confinement and magnetospheric properties, and magnetic star evolution. Methods. We obtained high-resolution spectropolarimetric observations of a large number of OB stars thanks to three large programs (LP) of observations that have been allocated on the high-resolution spectropolarimeters ESPaDOnS, Narval, and the polarimetric module HARPSpol of the HARPS spectrograph. We report here on the methods and first analysis of the HARPSpol magnetic detections. We identified the magnetic stars using a multi-line analysis technique. Then, when possible, we monitored the new discoveries to derive their rotation periods, which are critical for follow-up and magnetic mapping studies. We also performed a first-look analysis of their spectra and identified obvious spectral anomalies (e.g., surface abundance peculiarities, Hα emission), which are also of interest for future studies. Results. In this paper, we focus on eight of the 11 stars in which we discovered or confirmed a magnetic field from the HARPSpol LP sample (the remaining three were published in a previous paper). Seven of the fields were detected in early-type Bp stars, while the last field was detected in the Ap companion of a normal early B-type star. We report obvious spectral and multiplicity properties, as well as our measurements of their longitudinal field strengths, and their rotation periods when we are able to derive them. We also discuss the presence or absence of Hα emission with respect to the theory of centrifugally-supported magnetospheres.

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“…Here we assumed a wind mass-loss rateṀ = 4 × 10 −10 M year −1 and a wind terminal velocity v ∞ = 1700 km s −1 , as predicted from NLTE wind models (Krtička & Kubát 2010). The typical spindown time as a result of angular momentum loss via the magnetized stellar wind is about 6 Myr (ud-Doula et al 2009), which can be measurable with a sufficiently long time span (Mikulášek et al 2011).…”

Section: Are Co-rotating Circumstellar Clouds Needed?mentioning

confidence: 99%

Ultraviolet and visual flux and line variations of one of the least variable Bp stars HD 64740

Krtička

Janík

Marková

et al. 2013

A&A

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Context. The light variability of hot magnetic chemically peculiar stars is typically caused by the flux redistribution in spots with peculiar abundance. This raises the question why some stars with surface abundance spots show significant rotational light variability, while others do not. Aims. We study the Bp star HD 64740 to investigate how its remarkable inhomogeneities in the surface distribution of helium and silicon, and the corresponding strong variability of many spectral lines, can result in one of the faintest photometric variabilities among the Bp stars. Methods. We used model atmospheres and synthetic spectra calculated for the silicon and helium abundances from surface abundance maps to predict the ultraviolet and visual light and line variability of HD 64740. The predicted fluxes and line profiles were compared with the observed ones derived with the IUE, HST, and Hipparcos satellites and with spectra acquired using the FEROS spectrograph at the 2.2 m MPG/ESO telescope in La Silla. Results. We are able to reproduce the observed visual light curve of HD 64740 assuming an inhomogeneous distribution of iron correlated with silicon distribution. The light variations in the ultraviolet are hardly detectable. We detect the variability of many ultraviolet lines of carbon, silicon, and aluminium and discuss the origin of these lines and the nature of their variations. Conclusions. The maximum abundances of helium and silicon on the surface of HD 64740 are not high enough to cause significant light variations. The detected variability of many ultraviolet lines is most likely of atmospheric origin and reflects the inhomogeneous elemental surface distribution. The variability of the C iv resonance lines of carbon is stronger and it probably results from the dependence of the wind mass-loss rate on the chemical composition and magnetic field orientation. We have not been able to detect a clear signature of the matter trapped in the circumstellar clouds.

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The Rigidly Rotating Magnetosphere of σ Orionis E

Cited by 129 publications

References 21 publications

Magnetic Fields of Nondegenerate Stars

Magnetic Fields of Nondegenerate Stars

Discovery of new magnetic early-B stars within the MiMeS HARPSpol survey

Ultraviolet and visual flux and line variations of one of the least variable Bp stars HD 64740

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