Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/47555

Title

Deep advanced camera for surveys imaging in the globular cluster NGC 6397: the binary fraction

Author(s)

Davis, D. Saul;  Richer, Harvey B.;  Anderson, Jay;  Brewer, J. H.;  Hurley, J.;  Kalirai, Jasonjot S.;  Rich, R. Michael;  Stetson, Peter B.

Abstract

Using Hubble Space Telescope observations of the globular cluster NGC 6397, we constrain the cluster's binary fraction. The observations consist of two fields: the primary science field, a single Advanced Camera for Surveys (ACS) pointing centered approximately 5′ from the cluster center; and the parallel field, a single WFPC2 field centered on the cluster center. Using the exquisite photometric precision of these observations, we determine the binary fraction in these regions of the cluster by examining stars lying off the main sequence. The binary fraction is constrained to be 0.012 0.004 in the ACS field, and to be 0.051 0.010 in the WFPC field. N-body simulations by Hurley et al. in 2007 suggest that the binary fraction remains nearly constant beyond the half-mass radius for the lifetime of the cluster. In the context of these simulations, our results suggest that NGC 6397 had a primordial binary fraction of only 1%.

Publication type

Journal article

Research centre

Swinburne University of Technology. Faculty of Information and Communication Technologies. Centre for Astrophysics and Supercomputing

Source

Astronomical Journal, Vol. 135, no. 6 (Jun 2008), pp. 2155-2162

Publication year

2008

FOR Code(s)

0201 Astronomical and Space Sciences;  020103 Cosmology and Extragalactic Astronomy

Keyword(s)

Globular clusters;  NGC 6397;  Population II stars;  Stellar dynamics

Publisher

University of Chicago Press

ISSN

0004-6256

Publisher URL

http://dx.doi.org/10.1088/0004-6256/135/6/2155

Copyright

Copyright © 2008 The American Astronomical Society. All rights reserved.

Peer reviewed