Journal Article

An analysis of the blue straggler population in the Sgr dSph globular cluster Arp 2*

Giovanni Carraro and Anton F. Seleznev

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 412, issue 2, pages 1361-1366
Published in print April 2011 | ISSN: 0035-8711
Published online March 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.17996.x
An analysis of the blue straggler population in the Sgr dSph globular cluster Arp 2*

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We present and discuss new BVI CCD photometry in the field of the globular cluster Arp 2, which is considered a member of the Sagittarius dwarf spheroidal galaxy. The main goal of this investigation is to study the statistics and spatial distribution of blue straggler stars in the cluster. Blue stragglers are stars observed to be hotter and bluer than other stars with the same luminosity in their environments. As such, they appear to be much younger than the rest of the stellar population. Two main channels have been suggested to produce such stars: (1) collisions between stars in clusters; or (2) mass transfer between, or merger of, the components of primordial short-period binaries. The spatial distribution of these stars inside a star cluster, compared with the distribution of stars in different evolutionary stages, can cast light on the most efficient production mechanism at work. In the case of Arp 2, we found that blue straggler stars are significantly more concentrated than main-sequence stars, while they show the same degree of concentration as evolved stars (either red giants or horizontal branch stars). Since Arp 2 is not a very concentrated cluster, we suggest that this high central concentration is an indication that blue stragglers are mostly primordial binary stars.

Keywords: binaries: general; blue stragglers; stars: evolution; open clusters and associations: general; open clusters and associations: individual: Arp 2

Journal Article.  3486 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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