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Far-ultraviolet imaging of the globular cluster NGC 6681 with WFPC2We have imagined the globular cluster NGC 6681 in the far-UV and visible with Wide Field/Planetary Camera-2 (WFPC2) on the Hubble Space Telescope (HST). Our far-UV images show a sparsely populated and fully resolved central region, and we detect 122 stars. The far-UV to visible color-magnitude diagram shows a well-defined horizontal branch with no evidence for hot, more evolved descendants. We find one hot horizontal-branch star significantly below the model zero-age horizontal branch, but the rest are consistent with evolutionary models within uncertainties in calibration, distance, and reddening. The center of the cluster harbors two luminous blue stragglers. Our far-UV images graphically confirm that there is no steep density gradient at small radii among the horizontal-branch stars of this post-core-collapse cluster and show no evidence for significant color gradients.
Document ID
19950040560
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Watson, Alan M.
(Univ. of Wisconsin, Madison, WI United States)
Mould, Jeremy R.
(Australian National Univ. Weston Creek, Australia)
Gallagher, John S., III
(Univ. of Wisconsin, Madison, WI United States)
Ballester, Gilda E.
(Univ. of Michigan, Ann Arbor, MI United States)
Burrows, Christopher J.
(Space Telescope Science Inst. Baltimore, MD, United States)
Casertano, Stefano
(Johns Hopkins Univ. Baltimore, MD, United States)
Clarke, John T.
(Univ. of Michigan, Ann Arbor, MI United States)
Crisp, David
(Jet Propulsion Lab. Cal. Inst. of Tech., Pasadena, CA, United States)
Griffiths, Richard E.
(Johns Hopkins Univ. Baltimore, MD, United States)
Hester, J. Jeff
(Arizona State Univ. Tempe, AZ, United States)
Date Acquired
August 16, 2013
Publication Date
November 1, 1994
Publication Information
Publication: Astrophysical Journal, Part 2 - Letters
Volume: 435
Issue: 1
ISSN: 0004-637X
Subject Category
Astronomy
Accession Number
95A72159
Funding Number(s)
CONTRACT_GRANT: NAS7-1260
Distribution Limits
Public
Copyright
Other

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