Results 271 to 280 of about 22,441 (303)

Pre-main Sequence Stars

2007
Herbig Ae/Be stars are the early-type pre-main sequence stars. Normally they are simply abbreviated as HES (Herbig emission-line stars) or HAEBE (Herbig Ae Be stars). (1960) originally defined HES by the following characteristics: (i) The spectral type is A or earlier, with emission lines. (ii) The star lies in an obscured region.
Tomokazu Kogure, Kam-Ching Leung
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δ Scuti Pulsations in Pre-Main Sequence Stars

Astrophysics and Space Science, 2003
Intermediate mass pre-main sequence stars (1.5 to 5 M ⊙) cross the instability strip on their way to the main sequence. They are therefore expected to be pulsating in a similar way as the δ Scuti stars. In this review, I present the status of observational studies of pulsations in these stars, and comment on prospects for future investigations of these
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Pre-Main-Sequence Stages of Stars

Publications of the Astronomical Society of Japan, 1965
Abstract Evolutionary model sequences of gravitationally contracting stars were calculated for masses, 0.4, 0.6, 1.0, 1.5, 2.0 and 3.0 M⊙, by using the surface condition based on the conventional mixing length theory of convection and assuming the contraction to be homologous. The mixing length was assumed to be equal to 1-pressure scale
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An emission sequence in pre-main-sequence flare stars

Monthly Notices of the Royal Astronomical Society, 1991
Optical spectra of quiescent pre-main-sequence flare stars in Orion are presented. The spectra cover ∼3600-4600 A at ∼3 A resolution, and were taken using an optical fibre fed spectrograph. The spectra reveal that most of the stars have Ca II H and K and the Balmer lines in emission, and approximate surface fluxes for these lines are deduced, along ...
B. D. Carter, B. J. O'Mara
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Angular momentum evolution of low‐mass pre‐main sequence stars via extreme coronal mass ejections [PDF]

Astronomische Nachrichten, 2013
The angular momentum evolution of cool stars during the pre‐main sequence phase of stellar evolution remains a major outstanding problem. Multiple processes are likely involved in the transfer of mass and angular momentum within and out of the star+disk ...
K.G. Stassun, S.P. Matt, Aarnio, Alicia N., A.N. Aarnio, Matt, S. P., Stassun, K.G., Aarnio, A. N., Stassun, K. G., Matt, S.P.   +8 more
exaly   +2 more sources

Circumstellar Envelopes and Disks of Pre-Main Sequence Stars

Astrophysics and Space Science, 1995
The current state of knowledge about circumstellar matter of young stellar objects is briefly reviewed. It appears that some very young stars yet to accrete substantial amounts of mass may be seen through their dusty infalling envelopes even at optical wavelengths, because of the presence of holes or large departures from spherical symmetry in the ...
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Pre-main-sequence variable stars

2007
In section 2.19, we outlined what was presently known about star formation, and the early evolution of stars. There are several types of variability which are specifically or predominantly found among young stars. Most or all of these would be found in a given star, such as the sun, at various times in its pre-main-sequence (PMS) lifetime.
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Asteroseismology of pre-main sequence stars

2008
More than 30 years ago the first pulsating pre-main sequence (PMS) stars have been discov- ered. Since then, pulsations in 18 Herbig Ae stars and 18 members of young open clusters were detected and detailed asteroseismic investigations were conducted for some of them. We describe our latest results in this field.
Zwintz, Konstanze, Guenther, David B., Kallinger, Thomas   +2 more
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The Evolution of Pre-Main-Sequence Stars

1999
The location of optically visible Pre-Main-Sequence (PMS) stars in the H-R diagram combined with the use of theoretical evolutionary tracks have played a central role in stellar evolution studies since the initial work of Hayashi, Cameron and Iben in the early ′60s.
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The Chromospheres of Pre-Main Sequence Flare Stars

Publications of the Astronomical Society of Australia, 1989
AbstractOptical spectra of pre-main sequence flare stars in Orion are presented and analysed by the use of stellar chromospheric models. The stars observed divide into three groups on the basis of their quiescent spectra. The majority of the sample are similar to the dMe stars, with prominent Ca II and Balmer line emission.
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