Far-ultraviolet photometry of the globular cluster omega CEN

Whitney, J. H.; O’Connell, R. W.; Rood, Robert T.; Dorman, Ben; Landsman, W. B.; Cheng, K. P.; Bohlin, R. C.; Hintzen, P.; Roberts, M. S.; Smith, Andrew M.; Smith, E. P.; Stecher, T. P.

doi:10.1086/117157

Cited by 31 publications

(35 citation statements)

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“…HST observations of u Cen conÐrm the substantial population of sub-HB, EHB, and stars found AGB-manque by Whitney et al (1994) with UIT. About 32% of the HB consists of EHB stars and their descendants.…”

Section: Resultsmentioning

confidence: 82%

“…Binaries or the products of strong interactions in the cluster core would tend to be more concentrated to the cluster center. Instead, in the large-Ðeld (40@ diameter) UIT images of Whitney et al (1994), the radial distribution of u CenÏs EHB stars follows that of the rest of the HB stars. Our HST data suggest that the fraction of EHB stars increases outward from about 28%È33% in the inner two Ðelds to about 43% in the outer Ðeld.…”

Section: Spatial Distribution Of Hot Starsmentioning

confidence: 93%

“…The images discussed here are Wide Field Planetary Camera 2 (WFPC2) "" acquisition frames ÏÏ taken to conÐrm astrometry for a set of spectroscopic targets (to be discussed elsewhere) identiÐed on UIT far-UV images by Whitney et al (1994). three Ðelds is based on the position of stars for which UV spectra were obtained.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

“…(Evidence for multiple generations of star formation suggests that u Cen itself may even be a captured galaxy nucleus ; Hughes & Wallerstein 2000.) Its HB is extremely blue, and it contains the largest identiÐed population of EHB and of putative EHB-descendant stars lying above the HB (Dickens et al 1988 ;Bailyn et al 1992 ;Whitney et al 1994). We are particularly interested in investigating the reality of two unusual HB features found in lower precision far-UV photometry by the UIT : a hot HB gap and sub-HB stars (Whitney et al 1994).…”

Section: Introductionmentioning

confidence: 99%

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Hubble Space TelescopeObservations of New Horizontal‐Branch Structures in the Globular Cluster ω Centauri

D'Cruz

O’Connell

Rood

et al. 2000

ApJ

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The globular cluster u Centauri contains the largest known population of very hot horizontal-branch (HB) stars. We have used the Hubble Space T elescope to obtain a far-UV/optical color-magnitude diagram of three Ðelds in u Cen. We Ðnd that over 30% of the HB objects are "" extreme ÏÏ HB or hot post-HB stars. The hot HB stars are not concentrated toward the cluster center, which argues against a dynamical origin for them. A wide gap in the color distribution of the hot HB stars appears to correspond to gaps found earlier in several other clusters. This suggests a common mechanism, probably related to giant branch mass loss. The diagram contains a signiÐcant population of hot sub-HB stars, which we interpret as the "" blue-hook ÏÏ objects previously predicted by DÏCruz et al. These are produced by late He Ñashes in stars which have undergone unusually large giant branch mass loss. The cluster u Cen has a well-known spread of metal abundance, and our observations are consistent with a giant branch mass-loss efficiency which increases with metallicity.

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Section: Resultsmentioning

confidence: 82%

Section: Spatial Distribution Of Hot Starsmentioning

confidence: 93%

Section: Observations and Data Reductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hubble Space TelescopeObservations of New Horizontal‐Branch Structures in the Globular Cluster ω Centauri

D'Cruz

O’Connell

Rood

et al. 2000

ApJ

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“…From Figure 2 of Yanny et al (1994) one can readily appreciate the difficulty of measuring a distance modulus from an optical CMD. Strengthening the calibration of the FUV CMD potentially offers a more reliable distance (but see Whitney et al 1994, and references therein. )…”

Section: The Horizontal Branchmentioning

confidence: 99%

Far-Ultraviolet Imaging of the Globular Cluster NGC 7099 with the Second Wide-Field and Planetary Camera

Mould¹,

Watson²,

Gallagher³

et al. 1996

ApJ

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We have imaged the globular cluster NGC 7099 in the far-UV and visible with WFPC2 on the Hubble Space Telescope. Our far-UV images show a sparsely populated and fully resolved central region. The far-UV to visible color-magnitude diagram of these stars shows a well-defined horizontal branch with no evidence for hot, more evolved descendants. We find one hot horizontal branch star; the center of the cluster harbors four luminous blue stragglers. Far-UV images do not show any singularly steep density gradient at small radii among the horizontal branch stars of this post-core-collapse cluster.

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