Non-thermal velocities in the stellar wind of early-type stars

X-rays from early-type stars are emitted by the corona or the stellar wind. The materials in the surface layer of early-type stars are not contaminated by nuclear reactions in the stellar inside. Therefore, abundance study of the early-type stars provides us an information of the abundances of the original gas. However, the X-ray observations indicate low-metallicity, which is about 0.3 times of cosmic abundances. This fact raises the problem on the cosmic abundances.

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Photospheric and “Chromospheric” CIV Lines in B-Main-Sequence Stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900148788 ◽

1986 ◽

Vol 116 ◽

pp. 113-116

Author(s):

Fiorella Castelli ◽

Carlo Morossi ◽

Roberto Stalio

Keyword(s):

High Temperature ◽

Stellar Wind ◽

High Velocity ◽

Main Sequence ◽

Stellar Atmosphere ◽

Uv Spectra ◽

Spectral Lines ◽

Early Type ◽

Main Sequence Stars ◽

Early Type Stars

The presence in the far-UV spectra of early-type stars of spectral lines of superionized atoms is argument of controversial debate among astronomers. Presently there is agreement on the non-radiative origin of these ions but not on the proposed mechanisms for their production nor on the proposed locations in the stellar atmosphere where they are abundant. Cassinelli et al. (1978) suggest that the Auger mechanism is operative in a cool wind blowing above a narrow corona to produce these ions; Lucy and White (1980) introduce radiative instabilities growing into hot blobs distributed across the stellar wind; Doazan and Thomas (1982) make these ions to be formed in both pre- and post-coronal, high temperature regions at low and high velocity respectively.

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Be Phenomena in Young Early-type Stars: Various Forms of Interaction between the Star and the Circumstellar Gaseous Envelope

International Astronomical Union Colloquium ◽

10.1017/s0252921100056116 ◽

2000 ◽

Vol 175 ◽

pp. 344-347

Author(s):

M. Pogodin

Keyword(s):

High Resolution ◽

Stellar Wind ◽

Main Sequence ◽

Stellar Surface ◽

High Resolution Spectroscopy ◽

Evolutionary Status ◽

Be Stars ◽

Early Type ◽

Early Type Stars ◽

Gaseous Envelope

AbstractNew results of high-resolution spectroscopy of four pre-main sequence Ae/Be stars are presented. An analysis of parameters of lines originating in different regions of the circumstellar (CS) envelope (Hα, Hβ, He I 5876, DNal) allows to reconstruct a picture of the interaction between the star and the CS environment which can be displayed in different forms. At least two separate processes seem to impact the structural and kinematical properties of the envelope: the stellar wind from the stellar surface and the matter infall onto the star from the CS media. A possible relation between these two phenomena is discussed in the framework of different models. Some similarity between observational phenomena in Herbig Ae/Be and classical Be stars is noted in spite of their difference in evolutionary status.

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Radio and X-Ray Emissions from Chemically Peculiar B- and A-Type Stars: Observations and a Model

International Astronomical Union Colloquium ◽

10.1017/s0252921100020972 ◽

1993 ◽

Vol 138 ◽

pp. 507-516 ◽

Cited By ~ 1

Author(s):

Jeffrey L. Linsky

Keyword(s):

Energy Source ◽

Stellar Wind ◽

Mechanical Energy ◽

Early Type ◽

Late Type ◽

X Ray ◽

Nonthermal Radio ◽

Chemically Peculiar ◽

Early Type Stars

AbstractConventional wisdom holds that early-type and late-type stars have very different outer atmospheres, because the early-type stars lack deep convective zones. I argue that the magnetic chemically peculiar (CP) stars hotter than about spectral type A2 display many of the activity phenomena seen in the most active late-type stars. In particular, many CP stars are luminous nonthermal radio and coronal x-ray sources like the RS CVn systems. A wind-fed magnetosphere model has been proposed to explain both the nonthermal radio and the x-ray emission. In this model the stellar wind plays the role of a mechanical energy source analogous to the role played by convection in the active late-type stars.

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Discovery of weak magnetic fields in early B-type stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900212023 ◽

2003 ◽

Vol 212 ◽

pp. 202-203 ◽

Cited By ~ 5

Author(s):

Huib F. Henrichs ◽

Coralie Neiner ◽

Vincent C. Geers

Keyword(s):

Magnetic Properties ◽

Stellar Wind ◽

Magnetic Measurements ◽

Magnetic Phase ◽

Model Atmosphere ◽

Early Type ◽

Chemical Abundance ◽

Weak Magnetic Fields ◽

Magnetic Dipole Field ◽

Early Type Stars

We summarize recent results of magnetic measurements of three bright early B-type stars, β Cep, ζ Cas, and V2052 Oph, which were found to be oblique rotators with a weak magnetic dipole field with typical strength of a few hundred Gauss. From stellar wind studies we could derive their rotational periods very accurately, and match the stellar wind with the magnetic phase. From model atmosphere fits we derive the angles of rotational and magnetic axis. All three stars show some chemical abundance anomaly, presumably associated with the magnetic properties. The stars are also pulsating variables. This is of high asteroseismological interest, since these are the only early-type stars known with observationally determined rotation, pulsation and magnetic properties.

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A Search for Coronal Emission Lines from Early-Type Stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900034884 ◽

1988 ◽

Vol 132 ◽

pp. 123-125

Author(s):

D. Baade ◽

L. B. Lucy

Keyword(s):

Stellar Wind ◽

Controversial Issue ◽

Emission Lines ◽

Stellar Winds ◽

Early Type ◽

Wind Model ◽

Coronal Emission ◽

Early Type Stars ◽

Hot Corona

For more than ten years now, a controversial issue in studies of stellar winds has concerned the existence or not of a coronal zone (T ∼ 106 K) at the base of the cool winds (T ∼ Teff) of early-type stars. The latest revival of interest in this possibility is due to Wolfire et al. (1985) who showed that Waldron's (1984) recombination stellar wind (RSW) version of the hot corona – cool wind model (Hearn 1975; Cassinelli et al. 1978) yields models for ξ Puppis (O4 If) that are consistent with both IRAS and Einstein IPC data, thus refuting an earlier claim (Lamers et al. 1984) to have excluded the existence of a coronal zone.

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Recombination stellar wind model for the coronae of early-type stars

The Astrophysical Journal ◽

10.1086/162198 ◽

1984 ◽

Vol 282 ◽

pp. 256 ◽

Cited By ~ 49

Author(s):

W. L. Waldron

Keyword(s):

Stellar Wind ◽

Early Type ◽

Wind Model ◽

Early Type Stars

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X-ray diagnostics of massive star winds

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317002952 ◽

2016 ◽

Vol 12 (S329) ◽

pp. 151-155

Author(s):

L. M. Oskinova ◽

R. Ignace ◽

D. P. Huenemoerder

Keyword(s):

High Resolution ◽

Stellar Wind ◽

Massive Star ◽

Massive Stars ◽

Stellar Winds ◽

X Rays ◽

Early Type ◽

Stellar Rotation ◽

X Ray ◽

Early Type Stars

AbstractObservations with powerful X-ray telescopes, such as XMM-Newton and Chandra, significantly advance our understanding of massive stars. Nearly all early-type stars are X-ray sources. Studies of their X-ray emission provide important diagnostics of stellar winds. High-resolution X-ray spectra of O-type stars are well explained when stellar wind clumping is taking into account, providing further support to a modern picture of stellar winds as non-stationary, inhomogeneous outflows. X-ray variability is detected from such winds, on time scales likely associated with stellar rotation. High-resolution X-ray spectroscopy indicates that the winds of late O-type stars are predominantly in a hot phase. Consequently, X-rays provide the best observational window to study these winds. X-ray spectroscopy of evolved, Wolf-Rayet type, stars allows to probe their powerful metal enhanced winds, while the mechanisms responsible for the X-ray emission of these stars are not yet understood.

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