scholarly journals Emission-line widths and stellar-wind flows in T Tauri stars

1986 ◽  
Vol 222 (2) ◽  
pp. 213-221 ◽  
Author(s):  
C. Sá ◽  
M. V. Penston ◽  
M. T. V. T. Lago
Keyword(s):  
Emission Line ◽  
Stellar Wind ◽  
T Tauri Stars ◽  
T Tauri ◽  
Wind Flows ◽  
Line Widths

scholarly journals Stellar wind flows in T Tauri stars

1987 ◽  
Vol 122 ◽  
pp. 105-106
Author(s):  
C. Sá ◽  
M.T.V.T. Lago ◽  
M.V. Penston
Keyword(s):  
Stellar Wind ◽  
General Pattern ◽  
T Tauri Stars ◽  
Emission Lines ◽  
High Dispersion ◽  
T Tauri ◽  
Wind Flows ◽  
Using Data

Following the successful modelling of the wind from RU Lupi using data at moderate and high dispersion we report on similar observations of other T Tauri stars where the general pattern of the wind, as deduced from the widths of the emission lines of the various species, seems to be similar.

Stellar Wind Flows in T Tauri Stars

1987 ◽  
pp. 105-106
Author(s):  
C. Sá ◽  
M. T. V. T. Lago ◽  
M. V. Penston
Keyword(s):  
Stellar Wind ◽  
T Tauri Stars ◽  
T Tauri ◽  
Wind Flows

scholarly journals On the Nature and Origin of the T Tauri Stars

1957 ◽  
Vol 3 ◽  
pp. 3-10 ◽  
Author(s):  
George H. Herbig
Keyword(s):  
Emission Line ◽  
T Tauri Stars ◽  
New Approach ◽  
T Tauri ◽  
Astrophysical Journal ◽  
Relationship Of ◽  
The Relationship ◽  
Material Form

It is fitting that, in opening this Symposium with a consideration of the T Tauri stars, we note that this month marks the tenth anniversary of the September 1945 issue of the Astrophysical Journal, in which appeared the remarkable pioneering paper by Alfred H. Joy that initiated the study of emission-line stars associated with nebulosity. This contribution opened a new approach to the study of the relationship of stars to their environment. Today, ten years later, the T Tauri stars and their interaction with nebular material form a topic whose significance we may not fully appreciate and whose opportunities have been as yet only superficially exploited.

scholarly journals Magnetic torques on T Tauri stars: Accreting versus non-accreting systems

2020 ◽  
Vol 643 ◽  
pp. A129 ◽  
Author(s):  
G. Pantolmos ◽  
C. Zanni ◽  
J. Bouvier
Keyword(s):  
Stellar Wind ◽  
T Tauri Stars ◽  
Stellar Surface ◽  
Stellar Winds ◽  
Strong Impact ◽  
Corotation Radius ◽  
T Tauri ◽  
Wide Range ◽  
Thermally Driven ◽  
Rotational Evolution

Context. Classical T Tauri stars (CTTs) magnetically interact with their surrounding disks, a process that is thought to regulate their rotational evolution. Aims. We compute torques acting on the stellar surface of CTTs that arise from different accreting (accretion funnels) and ejecting (stellar winds and magnetospheric ejections) flow components. Furthermore, we compare the magnetic braking due to stellar winds in two different systems: isolated (i.e., weak-line T Tauri and main-sequence) and accreting (i.e., classical T Tauri) stars. Methods. We use 2.5D magnetohydrodynamic, time-dependent, axisymmetric simulations that were computed with the PLUTO code. For both systems, the stellar wind is thermally driven. In the star-disk-interaction (SDI) simulations, the accretion disk is Keplerian, viscous, and resistive, and is modeled with an alpha prescription. Two series of simulations are presented, one for each system (i.e., isolated and accreting stars). Results. In classical T Tauri systems, the presence of magnetospheric ejections confines the stellar-wind expansion, resulting in an hourglass-shaped geometry of the outflow, and the formation of the accretion columns modifies the amount of open magnetic flux exploited by the stellar wind. These effects have a strong impact on the stellar-wind properties, and we show that the stellar-wind braking is more efficient in the SDI systems than in the isolated ones. We further derive torque scalings over a wide range of magnetic field strengths for each flow component in an SDI system (i.e., magnetospheric accretion and ejections, and stellar winds), which directly applies a torque on the stellar surface. Conclusions. In all the performed SDI simulations, the stellar wind extracts less than 2% of the mass accretion rate and the disk is truncated by up to 66% of the corotation radius. All simulations show a net spin-up torque. We conclude that in order to achieve a stellar-spin equilibrium, we need either more massive stellar winds or disks that are truncated closer to the corotation radius, which increases the torque efficiency of the magnetospheric ejections.

scholarly journals Polarization of Variable Stars

1971 ◽  
Vol 15 ◽  
pp. 11-31 ◽  
Author(s):  
K. Serkowski
Keyword(s):  
Interstellar Medium ◽  
Emission Line ◽  
White Dwarfs ◽  
Variable Stars ◽  
T Tauri Stars ◽  
Type Star ◽  
Red Giants ◽  
T Tauri ◽  
Rapid Changes ◽  
R Coronae Borealis Stars

The changes in stellar polarization with time were first discovered in 1958 by GRIGORYAN (1958) for the red supergiant µ Cephei. In subsequent year BEHR (1959) gave a hint in a footnote to his catalogue that the emission-line B-type star α Cas seems to have variable polarization. However, several years had to pass before these discoveries were confirmed and the changes in polarization with time for the red giants and supergiants and for the emission-line B-type stars were firmly established, first by the observations made by SHAKHOVSKOJ (1963, 1964) and then by COYNE, GEHRELS (1967) and the writer (SERKOWSKI 1966, 1968). The changes in polarization with time were also found for the RV Tauri and T Tauri stars, R Coronae Borealis stars, novae, Wolf-Rayet stars, and white dwarfs. The rapid changes in polarization with time indicate that the polarization is not produced in the interstellar medium but in the vicinity of a star; such polarization is called intrinsic.

scholarly journals Accretion in Very Low Mass Young Objects

2003 ◽  
Vol 211 ◽  
pp. 141-142
Author(s):  
James Muzerolle ◽  
Lynne Hillenbrand ◽  
César Briceño ◽  
Nuria Calvet ◽  
Lee Hartmann
Keyword(s):  
Emission Line ◽  
T Tauri Stars ◽  
Line Profiles ◽  
Upper Limit ◽  
T Tauri ◽  
Accretion Rates ◽  
Hα Emission ◽  
Optical Continuum ◽  
Low Mass ◽  
Gas Accretion

We have investigated evidence for active accretion in a sample of ~ 30 young, very low mass objects, including at least 10 brown dwarfs. About 30% of the sample exhibits broad, asymmetric Hα emission line profiles, indicative of gas accretion via magnetospheric infall. There is a distinct lack of associated optical continuum veiling in these accretors, suggesting very low mass accretion rates. Our models yield an upper limit to the accretion rates that is several orders of magnitude smaller than typical of higher-mass T Tauri stars, suggesting a dependence of accretion rates with stellar mass.

scholarly journals Surveys for Hα Emission-Line Stars using the Bosscha Schmidt Telescope

1995 ◽  
Vol 148 ◽  
pp. 388-394
Author(s):  
Bambang Hidayat ◽  
Katsuo Ogura ◽  
Masao Shinohara
Keyword(s):  
Emission Line ◽  
Planetary Nebulae ◽  
T Tauri Stars ◽  
Schmidt Telescope ◽  
Dark Clouds ◽  
T Tauri ◽  
Hα Emission ◽  
Objective Prism ◽  
Emission Stars

According to McCarthy (1984) the objects detected in objective prism surveys for Hα emission line are a ”most unnatural“ group. Of course they consist of many natural groupings whose identities or other peculiarities could become apparent after observing them with higher dispersion and resolution spectroscopy. In some cases, however, their galactic locations and associations with other known populations, can provide a clue to their population types.The aims of the objective prism surveys using the Bosscha Schmidt telescope can be broadly categorised as follows: 1.Searches for galactic planetary nebulae in the region 240° < l < 360 °; |b| ≤ 10°, initiated by The (1968).2.Searches for T-Tauri stars in some southern dark clouds (Shinohara, Ogura & Hidayat 1989).3.Searches for variations in Hα intensities and luminous emission stars in some selected galactic regions, such as in the Puppis and Carina regions.

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