The blue straggler star population in NGC 6229†

  1. N. Sanna1,2,*,
  2. E. Dalessandro1,
  3. B. Lanzoni1,
  4. F. R. Ferraro1,
  5. G. Beccari3,
  6. R. T. Rood2

Article first published online: 6 MAR 2012

DOI: 10.1111/j.1365-2966.2012.20690.x

Issue

Monthly Notices of the Royal Astronomical Society

Monthly Notices of the Royal Astronomical Society

Volume 422, Issue 2, pages 1171–1177, May 2012

Additional Information

How to Cite

Sanna, N., Dalessandro, E., Lanzoni, B., Ferraro, F. R., Beccari, G. and Rood, R. T. (2012), The blue straggler star population in NGC 6229. Monthly Notices of the Royal Astronomical Society, 422: 1171–1177. doi: 10.1111/j.1365-2966.2012.20690.x

Author Information

  1. 1

    Dipartimento di Astronomia, Università degli Studi di Bologna, via Ranzani 1, I-40127 Bologna, Italy

  2. 2

    Astronomy Department, University of Virginia, PO Box 400325, Charlottesville, VA 22904, USA

  3. 3

    European Southern Obseervatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei Munchen, Germany

* Based on observations with the NASA/ESA HST (Prop. 11975), obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555. Also based on observations with MegaPrime/MegaCam, a joint project of Canada–France–Hawaii Telescope (CFHT) and CEA/DAPNIA, at the CFHT, which is operated by the National Research Council (NRC) of Canada, the Institute National des Sciences de l’Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.
E-mail: nicoletta.sanna2@unibo.it

Publication History

  1. Issue published online: 25 APR 2012
  2. Article first published online: 6 MAR 2012
  3. Accepted 2012 February 3. Received 2012 February 2; in original form 2011 November 17

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Keywords:

  • binaries: general;
  • blue stragglers;
  • stars: evolution;
  • globular clusters: individual: NGC 6229

ABSTRACT

We have used a combination of high-resolution Hubble Space Telescope Wide Field Planetary Camera 2 and wide-field ground-based observations in ultraviolet and optical bands to study the blue straggler star (BSS) population of the outer halo globular cluster NGC 6229 over its entire radial extent. A total of 64 bright BSS (with m255≤ 21.30, corresponding to m555≤ 20.75) has been identified. The BSS-projected radial distribution is found to be bimodal, with a high central peak, a well-defined minimum at intermediate radii (r∼ 40 arcsec) and an upturn in the outskirts. From detailed star counts even in the very inner region, we compute the centre of gravity of the cluster and the most accurate and extended radial density profile ever published for this system. The profile is reasonably well reproduced by a standard King model with an extended core (rc≃ 9.5 arcsec) and a modest value of the concentration parameter (c≃ 1.49). However, a deviation from the model is noted in the most external region of the cluster (at r > 250 arcsec from the centre). This feature needs to be further investigated in order to assess the possible presence of a tidal tail in this cluster.

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