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The evolution of angular momentum among zero-age main-sequence solar-type starsWe consider a survey of rotation among F, G, and K dwarfs of the Pleiades in the context of other young clusters (Alpha Persei and the Hyades) and pre-main-sequence (PMS) stars (in Taurus-Auriga and Orion) in order to examine how the angular momentum of a star like the sun evolves during its early life on the main sequence. The rotation of PMS stars can be evolved into distributions like those seen in the young clusters if there is only modest, rotation-independent angular momentum loss prior to the ZAMS. Even then, the ultrafast rotators (UFRs, or ZAMS G and K dwarfs with v sin i equal to or greater than 30 km/s) must owe their extra angular momentum to their conditions of formation and to different angular momentum loss rates above a threshold velocity, for it is unlikely that these stars had angular momentum added as they neared the ZAMS, nor can a spread in ages within a cluster account for the range of rotation seen. Only a fraction of solar-type stars are thus capable of becoming UFRs, and it is not a phase that all stars experience. Simple scaling relations (like the Skumanich relation) applied to the observed surface rotation rates of young solar-type stars cannot reproduce the way in which the Pleiades evolve into the Hyades. We argue that invoking internal differential rotation in these ZAMS stars can explain several aspects of the observations and thus can provide a consistent picture of ZAMS angular momentum evolution.
Document ID
19930053792
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Soderblom, David R.
(Space Telescope Science Inst. Baltimore, MD, United States)
Stauffer, John R.
(Harvard-Smithsonian Center for Astrophysics Cambridge, MA, United States)
Macgregor, Keith B.
(High Altitude Observatory Boulder, CO, United States)
Jones, Burton F.
(Lick Observatory Santa Cruz, CA, United States)
Date Acquired
August 16, 2013
Publication Date
June 1, 1993
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 409
Issue: 2
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
93A37789
Distribution Limits
Public
Copyright
Other

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