Wind circulation in selected rotating magnetic early-B stars

Smith, M. A.; Groote, D.

doi:10.1051/0004-6361:20010472

Cited by 42 publications

(57 citation statements)

References 37 publications

(44 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the latter case it should appear as emission peaking at high velocity, as the plasma is projected on either side of the disk (Smith & Groote 2001). Fig.…”

Section: Magnetospherementioning

confidence: 93%

The magnetic field and spectral variability of the He-weak star HR 2949

Shultz

Rivinius

Folsom

et al. 2015

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We analyze a high resolution spectropolarimetric dataset collected for the He-weak B3p IV star HR 2949. The Zeeman effect is visible in the circularly polarized component of numerous spectral lines. The longitudinal magnetic field varies between approximately −650 and +150 G. The polar strength of the surface magnetic dipole is calculated to be 2.4 +0.3 −0.2 kG. The star has strong overabundances of Fe-peak elements, along with extremely strong overabundances of rare-earth elements; however, He, Al, and S are underabundant. This implies that HR 2949 is a chemically peculiar star. Variability is seen in all photospheric lines, likely due to abundance patches as seen in many Ap/Bp stars. Longitudinal magnetic field variations measured from different spectral lines yield different results, likely a consequence of uneven sampling of the photospheric magnetic field by the abundance patches. Analysis of photometric and spectroscopic data for both HR 2949 and its companion star, HR 2948, suggests a revision of HR 2949's fundamental parameters: in particular, it is somewhat larger, hotter, and more luminous than previously believed. There is no evidence of optical or ultraviolet emission originating in HR 2949's magnetosphere, despite its moderately strong magnetic field and relatively rapid rotation; however, when calculated using theoretical and empirical boundaries on the initial rotational velocity, the spindown age is compatible with the stellar age. With the extensive phase coverage presented here, HR 2949 will make an excellent subject for Zeeman Doppler Imaging.

show abstract

“…In the latter case it should appear as emission peaking at high velocity, as the plasma is projected on either side of the disk (Smith & Groote 2001). Fig.…”

Section: Magnetospherementioning

confidence: 93%

The magnetic field and spectral variability of the He-weak star HR 2949

Shultz

Rivinius

Folsom

et al. 2015

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…Bp stars are well-known for their magnetically confined circumstellar clouds (Landstreet & Borra 1978;Nakajima 1985;Smith & Groote 2001;. The matter lifted by the wind from the atmosphere flows along the magnetic field lines and accumulates in the local effective potential minima at individual field lines.…”

Section: Are Co-rotating Circumstellar Clouds Needed?mentioning

confidence: 99%

“…The wind can fill stellar magnetospheres in the presence of the magnetic field, creating magnetospheric clouds (Landstreet & Borra 1978;Shore & Brown 1990;Smith & Groote 2001;.…”

Section: Introductionmentioning

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

View full text Add to dashboard Cite

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.

show abstract

“…This process causes the accumulation of cold dense material, which has been assumed for simplicity as a homogeneous torus with a circular cross-section surrounding the star (Babel & Montmerle 1997;Smith & Groote 2001).…”

Section: Basic Picturementioning

confidence: 99%

Stellar magnetosphere reconstruction from radio data

Leto¹,

Trigilio

Buemi

et al. 2006

A&A

View full text Add to dashboard Cite

Aims. In order to fully understand the physical processes in the magnetospheres of the Magnetic Chemically Peculiar stars, we performed multi-frequency radio observations of CU Virginis. The radio emission of this kind of stars arises from the interaction between energetic electrons and magnetic field. Our analysis is used to test the physical scenario proposed for the radio emission from the MCP stars and to derive quantitative information about physical parameters not directly observable. Methods. The radio data were acquired with the VLA and cover the whole rotational period of CU Virginis. For each observed frequency the radio light curves of the total flux density and fraction of circular polarization were fitted using a three-dimensional MCP magnetospheric model simulating the stellar radio emission as a function of the magnetospheric physical parameters. Results. The observations show a clear correlation between the radio emission and the orientation of the magnetosphere of this oblique rotator. The radio emission is explained as the result of the acceleration of the wind particles in the current sheets just beyond the Alfvén radius, that eventually return toward the star following the magnetic field and emitting radiation by gyrosyncrotron mechanisms. The accelerated electrons we probed with our simulations have a hard energetic spectrum (N(E) ∝ E −2 ) and the acceleration process has an efficiency of about 10 −3 . The Alfvén radius we determined is in the range of 12−17 R * and, for a dipolar field of 3000 Gauss at the magnetic pole of the star, we determine a mass loss from the star of about 10 −12 M yr −1 . In the inner magnetosphere, inside the Alfvén radius, the confined stellar wind accumulates and reaches temperatures in the range of 10 5 −10 6 K, and a detectable X-ray emission is expected.

show abstract

Wind circulation in selected rotating magnetic early-B stars

Cited by 42 publications

References 37 publications

The magnetic field and spectral variability of the He-weak star HR 2949

The magnetic field and spectral variability of the He-weak star HR 2949

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

Stellar magnetosphere reconstruction from radio data

Contact Info

Product

Resources

About