Results 221 to 230 of about 522,601 (266)
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2002
The matter in the Universe (its barionic component) is concentrated mainly in stars. Inside galaxies, stars contain more than 90% of the matter, and in galactic clusters, due to the existence of intercluster gas, stars contain more than 70% of the matter. The presence of heavy elements (heavier than carbon) in the intercluster gas, with an abundance of
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The matter in the Universe (its barionic component) is concentrated mainly in stars. Inside galaxies, stars contain more than 90% of the matter, and in galactic clusters, due to the existence of intercluster gas, stars contain more than 70% of the matter. The presence of heavy elements (heavier than carbon) in the intercluster gas, with an abundance of
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2012
In the last section we left the newly born star while it was still contracting in hydrostatic, but not yet thermal, equilibrium. Essential features of this contraction can already be understood by assuming simple homologous changes. It will turn out that the fate of such a sphere is mainly determined by the equation of state.
Rudolf Kippenhahn +2 more
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In the last section we left the newly born star while it was still contracting in hydrostatic, but not yet thermal, equilibrium. Essential features of this contraction can already be understood by assuming simple homologous changes. It will turn out that the fate of such a sphere is mainly determined by the equation of state.
Rudolf Kippenhahn +2 more
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1987
The IUE satellite has inaugurated a new era in the study of pre-main sequence (PMS) objects. IUE observations have revealed not just a new wavelength range but also a new temperature regime embracing physical phenomena that could not be studied before.
Catherine L. Imhoff, I. Appenzeller
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The IUE satellite has inaugurated a new era in the study of pre-main sequence (PMS) objects. IUE observations have revealed not just a new wavelength range but also a new temperature regime embracing physical phenomena that could not be studied before.
Catherine L. Imhoff, I. Appenzeller
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2015
In this final chapter we focus on binary populations amongst pre-main-sequence stars, namely the evolutionary phase between protostars and the main-sequence which includes both classical and weak-lined T Tauri stars. Our discussion begins by looking at the frequency of pre-main-sequence binaries as a function of environment as well as orbital period ...
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In this final chapter we focus on binary populations amongst pre-main-sequence stars, namely the evolutionary phase between protostars and the main-sequence which includes both classical and weak-lined T Tauri stars. Our discussion begins by looking at the frequency of pre-main-sequence binaries as a function of environment as well as orbital period ...
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Infrared companions to pre-main sequence stars
Astrophysics and Space Science, 1988We report 1.2, 1.6, 2.2 and 3.6 μm slit scan observations of the young low-luminosity stars Elias 22 (also known as GSS 31) in the Rho Ophiuchus dark cloud and Glass I in the Chamaeleon dark cloud. We discovered an infrared companion to Elias 22 at a projected separation of 2.0 arcsec (320 AU) and an optical/infrared companion to Glass I at a projected
H. Zinnecker +4 more
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2011
The time for the completion of protostellar evolution is effectively 2–3 times the free-fall time of the outer layers, which lies in the range 105–106 yr, depending on the initial density. As the accretion rate tapers off in the later phases and the infalling envelope becomes less and less opaque, the observable surface of the protostar declines in ...
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The time for the completion of protostellar evolution is effectively 2–3 times the free-fall time of the outer layers, which lies in the range 105–106 yr, depending on the initial density. As the accretion rate tapers off in the later phases and the infalling envelope becomes less and less opaque, the observable surface of the protostar declines in ...
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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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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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Pre‐main sequence stellar activity
Astronomische Nachrichten, 1984AbstractModels of stellar activity based on the α–ω dynamo have recently been proposed by BELVEDERE et al. (1980c, 1981b) for main sequence and giant late type stars.In the present work we extend the theoretical analysis to the pre‐main sequence fully convective phase of stellar evolution.
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1988
The observational work which has been done to date on young low-mass binaries is reviewed. Much effort is currently put into surveys of such binaries, and results from - as well as some limitations of - various techniques are discussed. Statistical analysis of a sufficiently large sample of pre-main sequence binaries will eventually provide essential ...
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The observational work which has been done to date on young low-mass binaries is reviewed. Much effort is currently put into surveys of such binaries, and results from - as well as some limitations of - various techniques are discussed. Statistical analysis of a sufficiently large sample of pre-main sequence binaries will eventually provide essential ...
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Pre Main Sequence Chromospheric Activity
1992We study the chromospheric evolution of low mass Pre Main Sequence Stars using the CaII line at 8542 A as a probe of stellar activity. Our sample consists mostly of classical T Tauri Stars (CTTS — WHα > 10 mA) and a few weak TTS (WTTS — WHA < 10 mA) with simultaneous observations from 4500 A up to 9000 A.
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