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Radial velocities of very low mass stars and candidate brown dwarf members of the Hyades and PleiadesWe have determined H alpha equivalent widths and radial velocities with 1 sigma accuracies of approximately 5 km s(exp -1) for approximately 20 candidate very low mass members of the Hyades and Pleiades clusters. The radial velocities for the Hyades sample suggest that nearly all of these stars are indeed highly probable members of the Hyades. The faintest stars in the Hyades sample have masses of order 0.1 solar mass. We also obtained radial velocities for four candidate very low mass members of the Pleiades and two objects that are candidate BD Pleiads. All of these stars have apparent V magnitudes fainter than the Hyades stars we observed, and the resultant radial velocity accuracy is worse. We believe that the three brighter stars are indeed likely very low mass stellar members of the Pleiades, whereas the status of the two brown dwarf candidates is uncertain. The Hyades stars we have observed and the three Pleiades very low mass stars are the lowest mass members of any open cluster whose membership has been confirmed by radial velocities and whose chromospheric activity has been measured. We see no change in chromospheric activity at the boundary where stars are expected to become fully convective (M approximately equals 0.3 solar mass) in either cluster. In the Pleiades, however, there may be a decrease in chromospheric activity for stars with (V-I)(sub K) greater than 3.5 (M less than or equal to 0.1 solar mass).
Document ID
19950029872
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Stauffer, John R.
(Smithsonian Astrophysical Observatory, Cambridge, MA United States)
Liebert, James
(Univ. of Arizona, Tucson, AZ United States)
Giampapa, Mark
(Nat. Solar Observatory, Tucson, AZ United States)
Macintosh, Bruce
(Univ. of California, Los Angeles, CA United States)
Reid, Neill
(California Inst. of Technology, Pasadena, CA United States)
Hamilton, Donald
(Max-Planck-Institut fur Astronomie Heidelberg, Germany)
Date Acquired
August 16, 2013
Publication Date
July 1, 1994
Publication Information
Publication: The Astronomical Journal
Volume: 108
Issue: 1
ISSN: 0004-6256
Subject Category
Astrophysics
Accession Number
95A61471
Funding Number(s)
CONTRACT_GRANT: NSF AST-92-17961
CONTRACT_GRANT: NAGW-2698
Distribution Limits
Public
Copyright
Other

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