The Giant, Horizontal, and Asymptotic Branches of Galactic Globular Clusters. I. The Catalog, Photometric Observables, and Features

Ferraro, F. R.; Messineo, M.; Pecci, F. Fusi; Palo, M. A. De; Straniero, O.; Chieffi, A.; Limongi, Marco

doi:10.1086/301029

Cited by 318 publications

(478 citation statements)

References 97 publications

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“…Consistent with these constraints, we adopt for our simulations an identical distance modulus for both NGC 288 and 362, with the actual value for Z \ 0.001 and for Harris (1996) and Ferraro et al (1999). Within the errors, these reddening values are also in reasonable agreement with the relative reddenings inferred from Paper I, namely, *E(V [I) \ ]0.015^0.014.…”

Section: Theoretical Frameworksupporting

confidence: 72%

“…1, but for NGC 288. In this case, the reddening value indicated, which is in excellent agreement with Harris (1996) and Ferraro et al (1999), was inferred by assuming NGC 288 to have the same distance modulus as derived for NGC 362 in A random sample of three simulations for this best-Ðtting combination of parameters is also displayed in Figure 4 (right column, middle and bottom). The upper regions of the observed CMD of NGC 288 (from Paper I) are also given in the top right panel ; the distance modulus employed was inferred in the same way as previously described for Z \ 0.001.…”

Section: Case Of Ngc 362supporting

confidence: 68%

“…It is important to note, in any case, that the number of ARBHB stars in NGC 288 is relatively smallÈless than ÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈ 7 Note that reddening uncertainties also introduce some leeway in the inferred di †erence in distance moduli (*k, following the notation of Paper I) between NGC 288 and 362 derived from Ðts of the data to theoretical ZAHBs : Experiments using the reddening values from Harris (1996 ; the 1999 June 22 version), Schlegel et al (1998), andFerraro et al (1999) clearly indicate that the *k value obtained by the ZAHB-Ðtting procedure is uncertain by^0.1 mag. We emphasize that the purpose of the present study is not to derive *k through ZAHB-Ðtting, but instead to analyze the "" horizontal ÏÏ distribution of stars along the HBs of NGC 288 and 362.…”

Section: Fig 4èas Inmentioning

confidence: 99%

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Age as the Second Parameter in NGC 288/NGC 362? II. The Horizontal Branch Revisited

Catelan¹,

Bellazzini²,

Landsman³

et al. 2001

The Astronomical Journal

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We revisit the "" second-parameter ÏÏ pair of globular clusters NGC 288/362 on the basis of theoretical models for red giant branch (RGB) and horizontal branch (HB) stars. The results of the most extensive set of RGB/HB simulations computed so far for these clusters are presented for two di †erent metallicities. Using several di †erent analytical mass-loss formulae for RGB stars, we derive relative "" HB morphology ages.ÏÏ We compare them with the relative main-sequence turno † ages derived by application of the "" bridge test ÏÏ in Paper I, where it was found that NGC 288 is 2^1 Gyr older than NGC 362. We Ðnd that adoption of a higher metallicity ([Fe/H] B [1.2), as favored by the Carretta & Gratton metallicity scale, makes age a much more plausible second-parameter candidate for this pair than is the case when a lower metallicity ([Fe/H] B [1.5), closer to the Zinn & West scale, is adopted. However, while the di †erent HB morphology of these two clusters can be reproduced by canonical HB models with [Fe/H] B [1.2 and an age di †erence of 2 Gyr, this explanation is not without difficulty. In particular, we conÐrm previous suggestions that canonical models are unable to reproduce the detailed HB morphology of NGC 288 at its red end, for as yet unknown reasons. Finally, we show that the mass dispersion on the HB of NGC 362 is substantially larger than for NGC 288 and suggest that there is a correlation between the mass dispersion on the HB phase and the central density of globular clusters. This is presumably related to the way environmental e †ects a †ect RGB mass lossÈanother major second-parameter candidate. We argue that, if conÐrmed, this central densityÈHB mass dispersion correlation will have to be taken into account in order to conclusively determine whether age may be considered the (sole) second parameter of HB morphology for this (and other) second-parameter pair(s).

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Section: Theoretical Frameworksupporting

confidence: 72%

Section: Case Of Ngc 362supporting

confidence: 68%

Section: Fig 4èas Inmentioning

confidence: 99%

See 1 more Smart Citation

Age as the Second Parameter in NGC 288/NGC 362? II. The Horizontal Branch Revisited

Catelan¹,

Bellazzini²,

Landsman³

et al. 2001

The Astronomical Journal

Self Cite

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“…Walker (1999) Rutledge, Hesser, & Stetson 1997 ;Ferraro et al 1999), and that is the value we adopt here. Recently, Bedin et al (2000) calculated the extinction and distance modulus for this cluster using several di †erent methods and metallicity assumptions.…”

Section: Cluster Parametersmentioning

confidence: 99%

Flash Mixing on the White Dwarf Cooling Curve: Understanding Hot Horizontal Branch Anomalies in NGC 2808

Brown

Sweigart

Lanz

et al. 2001

ApJ

197

394

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We present an ultraviolet color-magnitude diagram (CMD) spanning the hot horizontal branch (HB), blue straggler, and white dwarf populations of the globular cluster NGC 2808. These data were obtained with the far-UV and near-UV cameras on the Space Telescope Imaging Spectrograph (STIS). Although previous optical CMDs of NGC 2808 show a high-temperature gap within the hot HB population, no such gap is evident in our UV CMD. Instead, we Ðnd a population of hot subluminous HB stars, an anomaly only previously reported for the globular cluster u Cen. Our theoretical modeling indicates that the location of these subluminous stars in the UV CMD, as well as the high-temperature gap along the HB in optical CMDs, can be explained if these stars underwent a late helium-core Ñash while descending the white dwarf cooling curve. We show that the convection zone produced by such a late helium Ñash will penetrate into the hydrogen envelope, thereby mixing hydrogen into the hot helium-burning interior, where it is rapidly consumed. This phenomenon is analogous to the "" born again ÏÏ scenario for producing hydrogen-deÐcient stars following a late helium-shell Ñash. The Ñash mixing of the envelope greatly enhances the envelope helium and carbon abundances, and leads, in turn, to a discontinuous increase in the HB e †ective temperatures at the transition between canonical and Ñash-mixed stars. We argue that the hot HB gap is associated with this theoretically predicted dichotomy in the HB properties. Moreover, the changes in the emergent spectral energy distribution caused by these abundance changes are primarily responsible for explaining the hot subluminous HB stars. Although further evidence is needed to conÐrm that a late helium-core Ñash can account for the subluminous HB stars and the hot HB gap, we demonstrate that an understanding of these stars requires the use of appropriate theoretical models for their evolution, atmospheres, and spectra.

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“…Since its detection in 47 Tuc, the RGB bump has become the crossroads of several theoretical and observational investigations (Fusi Pecci et al 1990;Alves & Sarajedini 1999;Ferraro et al 1999;Zoccali et al 1999). In order to detect the bump, a large sample of RGB stars is required, ∼10 3 stars in the upper 4 magnitudes of the RGB according to Fusi Pecci et al (1990), and until a few years ago it was detected only in metal-rich stars.…”

Section: The Rgb Bump Brightnessmentioning

confidence: 99%

Red Giant Branch Stars: The Theoretical Framework

Salaris

Cassisi

Weiß

2002

PUBL ASTRON SOC PAC

177

172

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ABSTRACT. Theoretical predictions of red giant branch stars' effective temperatures, colors, luminosities, and surface chemical abundances are a necessary tool for the astrophysical interpretation of the visible-near-infrared integrated light from unresolved stellar populations, the color-magnitude diagrams of resolved stellar clusters and galaxies, and spectroscopic determinations of red giant chemical abundances. On the other hand, the comparison with empirical constraints provides a stringent test for the accuracy of present generations of red giant models.We review the current status of red giant star modeling, discussing in detail the still-existing uncertainties affecting the model input physics (e.g., electron conduction opacity, treatment of the superadiabatic convection) and the adequacy of the physical assumptions built into the model computations.We compare theory with several observational features of the red giant branch in Galactic globular clusters, such as the luminosity function "bump," the luminosity of the red giant branch tip, and the envelope chemical abundance patterns, to show the level of agreement between current stellar models and empirical data concerning the stellar luminosities, star counts, and surface chemical abundances.

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The Giant, Horizontal, and Asymptotic Branches of Galactic Globular Clusters. I. The Catalog, Photometric Observables, and Features

Cited by 318 publications

References 97 publications

Age as the Second Parameter in NGC 288/NGC 362? II. The Horizontal Branch Revisited

Age as the Second Parameter in NGC 288/NGC 362? II. The Horizontal Branch Revisited

Flash Mixing on the White Dwarf Cooling Curve: Understanding Hot Horizontal Branch Anomalies in NGC 2808

Red Giant Branch Stars: The Theoretical Framework

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