Wide‐Field CCD Photometry of the Globular Cluster M30

Sandquist, Eric L.; Bolte, Michael; Langer, G. E.; Hesser, J. E.; Oliveira, C. Mendes de

doi:10.1086/307268

Cited by 35 publications

(63 citation statements)

References 69 publications

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“…It has been recently pointed out that, at least for the metal-poor clusters, the agreement of the models with the observed LFs for the GGC stars is far from satisfactory (Faulkner & Swenson 1993 ;Bolte 1994 and references therein). Sandquist et al (1999), by comparing the LF of M30 with the theoretical LFs from Bergbusch & VandenBerg (1992) and VandenBerg et al (1999), conÐrm this result, at least for the most metal-poor clusters, and suggest that it might be the consequence of some deep-mixing events. On the other hand, Silvestri et al (1998) claim that their set of models strongly reduces the discrepancy with the observed LFs, though they cannot provide the reasons for the di †erences among the di †erent models.…”

Section: Luminosity Functionsmentioning

confidence: 82%

[ITAL]HUBBLE SPACE TELESCOPE[/ITAL] Observations of Galactic Globular Cluster Cores. II. NGC 6273 and the Problem of Horizontal-Branch Gaps

Piotto

Zoccali

King

et al. 1999

The Astronomical Journal

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We present observations of the center of the Galactic globular cluster NGC 6273, obtained with the Hubble Space T elescope Wide Field Planetary Camera 2 as part of the snapshot program GO-7470. A BV color-magnitude diagram (CMD) for D28,000 stars is presented and discussed. The most prominent feature of the CMD, identiÐed for the Ðrst time in this paper, is the extended horizontal-branch blue tail (EBT) with a clear double-peaked distribution and a signiÐcant gap. The EBT of NGC 6273 is compared with the EBTs of seven other globular clusters for which we have a CMD in the same photometric system. From this comparison, we conclude that all the globular clusters in our sample with an EBT show at least one gap along the horizontal branch, which could have similar origins. A comparison with theoretical models suggests that at least some of these gaps may be occurring at a particular value of the stellar mass, common to a number of di †erent clusters. From the CMD of NGC 6273 we obtain a distance modulusWe also estimate an average reddening \ 16.27^0.20. though the CMD is strongly a †ected by di †erential reddening, with the relative reddening spanning a *E(B[V ) D 0.2 mag in the WFPC2 Ðeld. A luminosity function for the evolved stars in NGC 6273 is also presented and compared with the most recent evolutionary models.

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Section: Luminosity Functionsmentioning

confidence: 82%

[ITAL]HUBBLE SPACE TELESCOPE[/ITAL] Observations of Galactic Globular Cluster Cores. II. NGC 6273 and the Problem of Horizontal-Branch Gaps

Piotto

Zoccali

King

et al. 1999

The Astronomical Journal

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“…A portion is shown here for guidance regarding its form and content. Sandquist et al (1999). Figures 12 and 13 present the results of the above calculations for 200 pixel (2A3) radial bins in both V and I bandpasses.…”

Section: Artificial Star Testsmentioning

confidence: 97%

The Luminosity Function and Color‐Magnitude Diagram of the Globular Cluster M12

Hargis

Sandquist

Bolte

2004

ApJ

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In this paper we present the V and I luminosity functions and color-magnitude diagrams derived from widefield (233) Galactic globular cluster M12. Using observed values (and ranges of values) for the cluster metallicity, reddening, distance modulus, and age, we compare these data with recent -enhanced stellar evolution models for low-mass metal-poor stars. We describe several methods of making comparisons between theoretical and observed luminosity functions to isolate the evolutionary timescale information that the luminosity functions contain. We find no significant evidence of excesses of stars on the red giant branch, although the morphology of the subgiant branch in the observed luminosity function does not match theoretical predictions in a satisfactory way. Current uncertainties in T eff -color transformations (and possibly also in other physics inputs to the models) make more detailed conclusions about the subgiant branch morphology impossible. Given the recent constraints on cluster ages from the WMAP experiment, we find that good-fitting models that do not include He diffusion (both color-magnitude diagrams and luminosity functions) are too old (by $1-2 Gyr) to adequately represent the cluster luminosity function. The inclusion of helium diffusion in the models provides an age reduction (compared with nondiffusive models) that is consistent with the age of the universe being 13:7 AE 0:2 Gyr.

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“…These fractions are assumed to be higher than the binary fraction of M30 at present day (about 7%, Milone et al 2012) because the binary fraction decreases with time due to the dynamical interactions and binary evolution (Ivanova et al 2005). In addition, the initial mass of M30 is simply assumed to be twice as massive as the current mass of M30 (log (M/M ⊙ )=5.3, Sandquist et al 1999) as the globular clusters may have lost a significant fraction of total mass driven by relaxation, stellar evolution and the tidal field of the Galaxy (Vesperini & Heggie 1997). Because the binaries are more difficult to lose from the globular clusters than single stars, the binary fraction in the lost stars is assumed to be half of the initial binary fraction.…”

Section: Binary Population Synthesismentioning

confidence: 99%

Contribution of Primordial Binary Evolution to the Two Blue-straggler Sequences in Globular Cluster M30

Jiang

Chen

et al. 2017

ApJ

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Two blue-straggler sequences discovered in globular cluster M30 provide a strong constraint on the formation mechanisms of blue stragglers. We study the formation of the blue-straggler binaries through binary evolution, and find that binary evolution can contribute to the blue stragglers in both of the sequences. Whether a blue straggler is located in the blue sequence or red sequence depends on the contribution of the mass donor to the total luminosity of the binary, which is generally observed as a single star in globular clusters. The blue stragglers in the blue sequence have a cool white-dwarf companion, while the majority (∼ 60%) of the objects in the red sequence are the binaries that are still experiencing mass transfer, but there are also some objects that the donors have just finished the mass transfer (the stripped-core stars, ∼ 10%) or the blue stragglers (the accretors) have evolved away from the blue sequence (∼ 30%). Meanwhile, W UMa contact binaries found in both sequences may be explained by various mass ratios, that is, W UMa contact binaries in the red sequence have two components with comparable masses (e.g. mass ratio q ∼ 0.3-1.0), while those in the blue sequence have low mass ratio (e.g. q < 0.3). However, the fraction of blue sequence in M30 cannot be reproduced by binary population synthesis if we assumed the initial parameters of a binary sample to be the same as that of the field. This possible indicates that dynamical effects on binary systems is very important in globular clusters.

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Wide‐Field CCD Photometry of the Globular Cluster M30

Cited by 35 publications

References 69 publications

[ITAL]HUBBLE SPACE TELESCOPE[/ITAL] Observations of Galactic Globular Cluster Cores. II. NGC 6273 and the Problem of Horizontal-Branch Gaps

[ITAL]HUBBLE SPACE TELESCOPE[/ITAL] Observations of Galactic Globular Cluster Cores. II. NGC 6273 and the Problem of Horizontal-Branch Gaps

The Luminosity Function and Color‐Magnitude Diagram of the Globular Cluster M12

Contribution of Primordial Binary Evolution to the Two Blue-straggler Sequences in Globular Cluster M30

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