Alfv�n wave-driving mechanism of late-type stellar wind

1990 ◽  
Vol 167 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Young Zheng ◽  
Li Xiao-Qing
Keyword(s):  
Stellar Wind ◽  
Driving Mechanism ◽  
Late Type ◽  
N Wave

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

1993 ◽  
Vol 138 ◽  
pp. 507-516 ◽  
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.

scholarly journals Stellar-wind theory for O and B stars

1970 ◽  
Vol 36 ◽  
pp. 236-237
Author(s):  
Philip M. Solomon
Keyword(s):  
Mass Loss ◽  
Radiation Pressure ◽  
Stellar Wind ◽  
Conclusive Evidence ◽  
Driving Mechanism ◽  
Gravitational Acceleration ◽  
Hot Stars ◽  
B Stars ◽  
Wind Theory ◽  
Ultraviolet Observations

The rocket-ultraviolet observations of strong Doppler-shifted absorption lines of Siiv, Civ, Nv and other ions in the spectrum of O and B supergiants clearly indicate a high velocity outflow of matter from these stars. The presence of moderate ionisation stages in the stellar wind is conclusive evidence that the flow cannot be due to a high temperature corona as is the case for the solar wind. It is shown that the driving mechanism for the hot-star mass loss is radiation pressure exerted on the gas through absorption in resonance lines occurring at wavelengths near the maximum of the star's continuum flux. In the upper layers of these stars the outward force per gram of matter due to the radiation pressure can greatly exceed the gravitational acceleration making a static atmosphere impossible.The problem of a steady-state moving reversing layer is formulated and the solution leads to predictions of mass-loss rates as a function of effective temperature and gravity for all hot stars. These results are in substantial agreement with the observations.

scholarly journals The masses of late-type WN stars

2006 ◽  
Vol 2 (14) ◽  
pp. 199-199
Author(s):  
Götz Gräfener ◽  
Wolf-Rainer Hamann
Keyword(s):  
Spectral Analysis ◽  
Hydrodynamic Model ◽  
Stellar Wind ◽  
Massive Stars ◽  
Late Type ◽  
Direct Estimate ◽  
The Galaxy ◽  
Wind Modeling ◽  
The Masses ◽  
Eddington Limit

AbstractWe present recent results for galactic WNL stars, obtained with the new Potsdam Wolf-Rayet (PoWR) hydrodynamic model atmospheres. Based on a combination of stellar wind modeling and spectral analysis we identify the galactic WNL subtypes as a group of extremely luminous stars close to the Eddington limit. Their luminosities imply progenitor masses around 120 M⊙ or even above, making them the direct descendants of the most massive stars in the galaxy. Because of the proximity to the Eddington limit our models are very sensitive to the L/M ratio, thus allowing for a direct estimate of the present masses of these objects.

YY Geminorum: A Very Late Type Close Binary with Possible Magnetic Stellar Wind

2002 ◽  
Vol 124 (2) ◽  
pp. 1060-1063 ◽  
Author(s):  
Shengbang Qian ◽  
Dengliang Liu ◽  
Wenli Tan ◽  
Boonrucksar Soonthornthum
Keyword(s):  
Stellar Wind ◽  
Close Binary ◽  
Late Type

scholarly journals Energy Losses by Stellar Activity Phenomena

1993 ◽  
Vol 137 ◽  
pp. 654-656 ◽  
Author(s):  
Maria Katsova
Keyword(s):  
Stellar Wind ◽  
Large Scale ◽  
Main Sequence ◽  
High Efficiency ◽  
Convection Zone ◽  
Energy Losses ◽  
Late Type ◽  
Dynamo Action ◽  
Stellar Flares ◽  
Transient Events

AbstractFor active late-type dwarfs, the total energy losses including both chromospheric and coronal radiation as well as the energy losses caused by stellar flares reach 3·10−3 L001. To maintain such high energetic losses requires a high efficiency of the dynamo action in the convection zone. Mass loss by active late-type stars can probably approach the rate of 10−11 M⊙/yr if we take into account the large-scale structure of their coronae and transient events. The phase of activity can continue for up to 1% of the lifetime of these stars on the main sequence due to braking by such a stellar wind.

scholarly journals Periods of Unevolved Late-Type Close Binaries: Evidence of Magnetic Activity

1983 ◽  
Vol 71 ◽  
pp. 391-392
Author(s):  
G. Giuricin ◽  
S. Catalano ◽  
F. Mardirossian ◽  
M. Mezzetti
Keyword(s):  
Angular Momentum ◽  
Orbital Angular Momentum ◽  
Stellar Wind ◽  
Magnetic Activity ◽  
Close Binaries ◽  
Late Type ◽  
Period Distribution ◽  
Short Period ◽  
Angular Momentum Loss ◽  
Magnetic Braking

ABSTRACTOur study of the period distribution of about 200 FGKM-type unevolved close binaries has revealed a strong deficit of short-period systems.This finding may be connected with the occurrence of a very efficient mechanism of orbital angular momentum loss via magnetic braking by stellar wind, in the earliest evolutionary phases.

scholarly journals Massive Contact Binary Systems

1991 ◽  
Vol 143 ◽  
pp. 207-212
Author(s):  
Kam-Ching Leung
Keyword(s):  
Mass Loss ◽  
Stellar Wind ◽  
Binary Stars ◽  
Binary Systems ◽  
Type Systems ◽  
Early Type ◽  
Late Type ◽  
Long Period ◽  
Massive Component ◽  
Contact Binary

In recent years very massive single stars have been found to be upward of 90 M⊙. Massive contact binary systems have been found among the early-type systems, but their masses are far less than those reported for single stars. The most massive component found is about 60 M⊙.It is generally believed that no late-type very massive stars have been detected (Humphreys and Davidson). This may be due to the large amount of mass loss from stellar wind. Recently, several extremely long-period late-type binary systems have been found to be contact systems. Two systems, UU Cnc and 5 Cet, have their primary components with masses exceeding 40 M⊙, and K spectra. This result tends to suggest that close or interacting binary stars may be able to preserve the mass loss from stellar wind within the binary systems.

scholarly journals X-ray observations of central stars of planetary nebulae and their winds

2011 ◽  
Vol 7 (S283) ◽  
pp. 204-210
Author(s):  
Martín A. Guerrero
Keyword(s):  
Stellar Wind ◽  
Mechanical Energy ◽  
Planetary Nebulae ◽  
Energy Output ◽  
X Rays ◽  
Late Type ◽  
Coronal Emission ◽  
X Ray ◽  
Ob Stars ◽  
Central Stars

AbstractThe photospheric emission from the hottest central stars of planetary nebulae (CSPNe) is capable to extend into the X-ray domain, with emission peaking at 0.1-0.2 keV and vanishing above 0.4 keV. Unexpected, intriguing hard X-ray emission with energies greater than 0.5 keV has been reported for several CSPNe and for a number of white dwarfs (WDs). Different mechanisms may be responsible for the hard X-ray emission from CSPNe and WDs: coronal emission from a late-type companion, shocks in fast winds as in OB stars, leakage from underneath the star photosphere, or accretion of material from a disk, a companion star, or the circumstellar medium. Therefore, the hard X-ray emission associated with CSPNe may have significant implications for our understanding of the formation of PNe: binary companions, disks, and magnetic fields are thought to play a major role in the shaping of PNe, whereas clumping in the stellar wind may have notable effects in the PN evolution by modifying the stellar mechanical energy output. Here I present the results of different observational efforts to search for hard X-ray emission from CSPNe and discuss the different mechanisms for the production of hard X-rays.

A Search for Dyson Spheres around Late-Type Stars in the Solar Neighborhood II

1997 ◽  
Vol 161 ◽  
pp. 707-709 ◽  
Author(s):  
Jun Jugaku ◽  
Shiro Nishimura
Keyword(s):  
Solar Neighborhood ◽  
The Sun ◽  
Late Type ◽  
Solar Type

AbstractWe continued our search for partial (incomplete) Dyson spheres associated with 50 solar-type stars (spectral classes F, G, and K) within 25 pc of the Sun. No candidate objects were found.

The12CO(1—0) to H2conversion factor in normal late-type galaxies

2002 ◽  
Vol 4 ◽  
pp. 393-393
Author(s):  
A. Boselli ◽  
J. Lequeux ◽  
G. Gavazzi
Keyword(s):  
Late Type
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