EDP Sciences
Free access
Issue A&A
Volume 481, Number 3, April III 2008
Page(s) 701 - 704
Section Galactic structure, stellar clusters, and populations
DOI http://dx.doi.org/10.1051/0004-6361:20079082
Published online 14 February 2008

A&A 481, 701-704 (2008)
DOI: 10.1051/0004-6361:20079082

Research Note

The correlation between blue straggler and binary fractions in the core of Galactic globular clusters

A. Sollima1, B. Lanzoni1, G. Beccari1, 2, F. R. Ferraro1, and F. Fusi Pecci2

1  Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy
    e-mail: antonio.sollima@oabo.inaf.it (AS)
2  INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy

(Received 16 November 2007 / Accepted 24 January 2008)

Context. Blue stragglers stars (BSSs) are thought to form in globular clusters by two main formation channels: i) mergers induced by stellar collisions; and ii) coalescence or mass transfer between companions in binary systems. The detailed study of the BSS properties is therefore crucial for understanding the binary evolution mechanisms and the complex interplay between dynamics and stellar evolution in dense stellar systems.
Aims. We present the first comparison between the BSS specific frequency and the binary fraction in the core of a sample of Galactic globular clusters, with the aim of investigating the relative efficiency of the two proposed formation mechanisms.
Methods. We derived the frequency of BSSs in the core of thirteen low-density Galactic globular clusters by using deep ACS@HST observations and investigated its correlation with the binary fraction and various other cluster parameters.
Results. We observed a correlation between the BSS specific frequency and the binary fraction. The significance of the correlation increases by including a further dependence on the cluster's central velocity dispersion.
Conclusions. We conclude that the unperturbed evolution of primordial binaries could be the dominant BSS formation process, at least in low-density environments.

Key words: techniques: photometric -- binaries: general -- blue stragglers -- stars: population II -- globular clusters: general

© ESO 2008

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Editor-in-Chief: T. Forveille
Letters Editor-in-Chief: J. Alves
Managing Editor: C. Bertout

ISSN: 0004-6361 ; e-ISSN: 1432-0746
Frequency: 12 volumes per year
Published by: EDP Sciences

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