Photometric Determination of the Mass Accretion Rates of Pre-main-sequence Stars. V. Recent Star Formation in the 30 Dor Nebula

AbstractAsteroseismology is a powerful tool to derive stellar parameters, including the helium content and internal helium gradients, and the macroscopic motions which can lead to lithium, beryllium, and boron abundance variations. Precise determinations of these parameters need deep analyses for each individual stars. After a general introduction on helio and asteroseismology, I first discuss the solar case, the results which have been obtained in the past two decades, and the crisis induced by the new determination of the abundances of heavy elements. Then I discuss asteroseismology in relation with light element abundances, especially for the case of main sequence stars.

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Empirical Determination of the Gravity-Darkening Exponent for the Secondary Components Filling the Roche Lobe in Semi-Detached Close Binary Systems

International Astronomical Union Colloquium ◽

10.1017/s0252921100093866 ◽

1988 ◽

Vol 108 ◽

pp. 217-218

Author(s):

Masatoshi Kitamura ◽

Yasuhisa Nakamura

Keyword(s):

Binary Systems ◽

Main Sequence ◽

Close Binary System ◽

Roche Lobe ◽

Close Binary ◽

Close Binaries ◽

Main Sequence Stars ◽

Local Gravity ◽

Subsurface Layers

The ordinary semi-detached close binary system consists of a main-sequence primary and subgiant (or giant) secondary component where the latter fills the Roche lobe. From a quantitative analysis of the observed ellipticity effect, Kitamura and Nakamura (1986) have deduced empirical values of the exponent of gravity-darkening for distorted main-sequence stars in detached systems and found that the empirical values of the exponent for these stars with early-type spectra are close to the unity, indicating that the subsurface layers of early-main sequence stars in close binaries are actually in radiative equilibrium. The exponent of gravity-darkening can be defined by H ∝ gα with H as the bolonetric surface brightness and g as the local gravity on the stellar surface.

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A comparison of the density gradients of main sequence stars obtained by two different methods in different galactic latitudes

Symposium - International Astronomical Union ◽

10.1017/s0074180900000620 ◽

1970 ◽

Vol 38 ◽

pp. 232-235

Author(s):

W. Becker ◽

R. Fenkart

Keyword(s):

Main Sequence ◽

Milky Way ◽

Absolute Magnitude ◽

Galactic Centre ◽

Density Gradients ◽

The Sun ◽

Main Sequence Stars

The Basel Observatory program of the determination of disc- and halo-density gradients for different intervals of absolute magnitude comprises in addition to Milky Way fields several directions, all pointing to Selected Areas near a plane perpendicular to the galactic equator and passing through the sun and the galactic centre. It was started with SA 51 (Becker, 1965) and continued with Sa 57, 54 and 141 (Fenkart, 1967, 1968, 1969).

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Coronagraphic imaging of pre-main-sequence stars: Remnant evvelopes of star formation seen in reflection

The Astronomical Journal ◽

10.1086/117351 ◽

1995 ◽

Vol 109 ◽

pp. 1181 ◽

Cited By ~ 39

Author(s):

Tadashi Nakajima ◽

David A. Golimowski

Keyword(s):

Star Formation ◽

Main Sequence ◽

Main Sequence Stars

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Circumstellar Disks and Star Formation

Highlights of Astronomy ◽

10.1017/s1539299600009229 ◽

1992 ◽

Vol 9 ◽

pp. 377-380

Author(s):

L. Hartmann ◽

M. Gomez ◽

S.J. Kenyon

Keyword(s):

Star Formation ◽

Spectral Region ◽

Main Sequence ◽

Circumstellar Disks ◽

Central Star ◽

Disk Accretion ◽

Main Sequence Stars ◽

Excess Emission ◽

Infrared Spectral ◽

The Masses

Results from the IRAS satellite showed that many pre-main sequence stars exhibited unexpectedly large fluxes in the infrared spectral region. Several studies have shown that the simplest and most satisfying explanation of this excess emission is that it arises in optically-thick, dusty, circumstellar disks (Rucinski 1985; Adams, Lada, and Shu 1987, 1988; Kenyon and Hartmann 1987; Bertout, Basri, and Bouvier 1988; Basri and Bertout 1989). The masses of these disks are estimated to range between 10-3M⊙ to 1M⊙ (Beckwith et al. 1990; Adams et al. 1990), large enough that disk accretion may have a significant effect on the evolution of the central star. Indeed, Mercer-Smith, Cameron, and Epstein (1984) suggested that stars are essentially completely accreted from disks, rather than formed from quasi-spherical accretion (Stabler 1983, 1988).

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