Far-ultraviolet imaging of the globular cluster NGC 6681 with WFPC2

Alan M. Watson, Jeremy R. Mould, John S. Gallagher, Gilda E. Ballester, Christopher J. Burrows, Stefano Casertano, John T. Clarke, David Crisp, Richard E. Griffiths, J. Jeff Hester, John G. Hoessel, Jon A. Holtzman, Paul Scowen, Karl R. Stapelfeldt, John T. Trauger, James A. Westphal

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

We have imaged the globular cluster NGC 6681 in the far-UV and visible with WFPC2 on the 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.

Original languageEnglish (US)
JournalAstrophysical Journal
Volume435
Issue number1 PART 2
StatePublished - Nov 1 1994

Fingerprint

horizontal branch stars
globular clusters
gradients
hot stars
harbors
color-magnitude diagram
harbor
diagram
calibration
color
stars
radii

Keywords

  • Globular clusters: individual: (NGC 6681)
  • Stars: evolution
  • Stars: horizontal-branch
  • Ultraviolet: stars

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Watson, A. M., Mould, J. R., Gallagher, J. S., Ballester, G. E., Burrows, C. J., Casertano, S., ... Westphal, J. A. (1994). Far-ultraviolet imaging of the globular cluster NGC 6681 with WFPC2. Astrophysical Journal, 435(1 PART 2).

Far-ultraviolet imaging of the globular cluster NGC 6681 with WFPC2. / Watson, Alan M.; Mould, Jeremy R.; Gallagher, John S.; Ballester, Gilda E.; Burrows, Christopher J.; Casertano, Stefano; Clarke, John T.; Crisp, David; Griffiths, Richard E.; Hester, J. Jeff; Hoessel, John G.; Holtzman, Jon A.; Scowen, Paul; Stapelfeldt, Karl R.; Trauger, John T.; Westphal, James A.

In: Astrophysical Journal, Vol. 435, No. 1 PART 2, 01.11.1994.

Research output: Contribution to journalArticle

Watson, AM, Mould, JR, Gallagher, JS, Ballester, GE, Burrows, CJ, Casertano, S, Clarke, JT, Crisp, D, Griffiths, RE, Hester, JJ, Hoessel, JG, Holtzman, JA, Scowen, P, Stapelfeldt, KR, Trauger, JT & Westphal, JA 1994, 'Far-ultraviolet imaging of the globular cluster NGC 6681 with WFPC2', Astrophysical Journal, vol. 435, no. 1 PART 2.
Watson AM, Mould JR, Gallagher JS, Ballester GE, Burrows CJ, Casertano S et al. Far-ultraviolet imaging of the globular cluster NGC 6681 with WFPC2. Astrophysical Journal. 1994 Nov 1;435(1 PART 2).
Watson, Alan M. ; Mould, Jeremy R. ; Gallagher, John S. ; Ballester, Gilda E. ; Burrows, Christopher J. ; Casertano, Stefano ; Clarke, John T. ; Crisp, David ; Griffiths, Richard E. ; Hester, J. Jeff ; Hoessel, John G. ; Holtzman, Jon A. ; Scowen, Paul ; Stapelfeldt, Karl R. ; Trauger, John T. ; Westphal, James A. / Far-ultraviolet imaging of the globular cluster NGC 6681 with WFPC2. In: Astrophysical Journal. 1994 ; Vol. 435, No. 1 PART 2.
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abstract = "We have imaged the globular cluster NGC 6681 in the far-UV and visible with WFPC2 on the 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.",
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AU - Burrows, Christopher J.

AU - Casertano, Stefano

AU - Clarke, John T.

AU - Crisp, David

AU - Griffiths, Richard E.

AU - Hester, J. Jeff

AU - Hoessel, John G.

AU - Holtzman, Jon A.

AU - Scowen, Paul

AU - Stapelfeldt, Karl R.

AU - Trauger, John T.

AU - Westphal, James A.

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N2 - We have imaged the globular cluster NGC 6681 in the far-UV and visible with WFPC2 on the 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.

AB - We have imaged the globular cluster NGC 6681 in the far-UV and visible with WFPC2 on the 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.

KW - Globular clusters: individual: (NGC 6681)

KW - Stars: evolution

KW - Stars: horizontal-branch

KW - Ultraviolet: stars

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