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A binary origin for ‘blue stragglers’ in globular clusters

A binary origin for ‘blue stragglers’ in globular clusters
A binary origin for ‘blue stragglers’ in globular clusters
Blue stragglers in globular clusters are abnormally massive stars that should have evolved off the stellar main sequence long ago. There are two known processes that can create these objects: direct stellar collisions and binary evolution.

However, the relative importance of these processes has remained unclear. In particular, the total number of blue stragglers found in a given cluster does not seem to correlate with the predicted collision rate, providing indirect support for the binary-evolution model.

Yet the radial distributions of blue stragglers in many clusters are bimodal, with a dominant central peak: this has been interpreted as an indication that collisions do dominate blue straggler production, at least in the high-density cluster cores.

Here we report that there is a clear, but sublinear, correlation between the number of blue stragglers found in a cluster core and the total stellar mass contained within it. From this we conclude that most blue stragglers, even those found in cluster cores, come from binary systems. The parent binaries, however, may themselves have been affected by dynamical encounters. This may be the key to reconciling all of the seemingly conflicting results found to date.
0028-0836
288-290
Knigge, Christian
ac320eec-631a-426e-b2db-717c8bf7857e
Leigh, Nathan
90069e68-a317-4cce-92e3-2401e3518751
Sills, Alison
2f7067f6-89a0-4738-b60e-a25e8b7a434d
Knigge, Christian
ac320eec-631a-426e-b2db-717c8bf7857e
Leigh, Nathan
90069e68-a317-4cce-92e3-2401e3518751
Sills, Alison
2f7067f6-89a0-4738-b60e-a25e8b7a434d

Knigge, Christian, Leigh, Nathan and Sills, Alison (2009) A binary origin for ‘blue stragglers’ in globular clusters. Nature, 457 (7227), 288-290. (doi:10.1038/nature07635).

Record type: Article

Abstract

Blue stragglers in globular clusters are abnormally massive stars that should have evolved off the stellar main sequence long ago. There are two known processes that can create these objects: direct stellar collisions and binary evolution.

However, the relative importance of these processes has remained unclear. In particular, the total number of blue stragglers found in a given cluster does not seem to correlate with the predicted collision rate, providing indirect support for the binary-evolution model.

Yet the radial distributions of blue stragglers in many clusters are bimodal, with a dominant central peak: this has been interpreted as an indication that collisions do dominate blue straggler production, at least in the high-density cluster cores.

Here we report that there is a clear, but sublinear, correlation between the number of blue stragglers found in a cluster core and the total stellar mass contained within it. From this we conclude that most blue stragglers, even those found in cluster cores, come from binary systems. The parent binaries, however, may themselves have been affected by dynamical encounters. This may be the key to reconciling all of the seemingly conflicting results found to date.

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More information

Published date: 15 January 2009
Organisations: Astronomy and Space Science

Identifiers

Local EPrints ID: 144183
URI: http://eprints.soton.ac.uk/id/eprint/144183
ISSN: 0028-0836
PURE UUID: 7de4f8f4-4212-43be-bb4b-1ba81c82da09

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Date deposited: 16 Apr 2010 15:16
Last modified: 25 Nov 2021 17:59

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Contributors

Author: Nathan Leigh
Author: Alison Sills

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