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A Chandra Study Of The Galactic Globular Cluster Omega Centauri

Haggard, Daryl; Cool, Adrienne M. and Davies, Melvyn B LU (2009) In Astrophysical Journal 697(1). p.224-236
Abstract
We analyze a similar to 70 ks Chandra Advanced CCD Imaging Spectrometer exposure of the globular cluster omega Cen (NGC 5139). The similar to 17' x 17' field of view fully encompasses three core radii and almost twice the half-mass radius. We detect 180 sources to a limiting flux of similar to 4.3 x 10(-16) erg cm(-2) s(-1) (L-x = 1.2 x 10(30) erg s(-1) at 4.9 kpc). After accounting for the number of active galactic nuclei and possible foreground stars, we estimate that 45-70 of the sources are cluster members. Four of the X-ray sources have previously been identified as compact accreting binaries in the cluster-three cataclysmic variables (CVs) and one quiescent neutron star. Correlating the Chandra positions with known variable stars... (More)
We analyze a similar to 70 ks Chandra Advanced CCD Imaging Spectrometer exposure of the globular cluster omega Cen (NGC 5139). The similar to 17' x 17' field of view fully encompasses three core radii and almost twice the half-mass radius. We detect 180 sources to a limiting flux of similar to 4.3 x 10(-16) erg cm(-2) s(-1) (L-x = 1.2 x 10(30) erg s(-1) at 4.9 kpc). After accounting for the number of active galactic nuclei and possible foreground stars, we estimate that 45-70 of the sources are cluster members. Four of the X-ray sources have previously been identified as compact accreting binaries in the cluster-three cataclysmic variables (CVs) and one quiescent neutron star. Correlating the Chandra positions with known variable stars yields eight matches, of which five are probable cluster members that are likely to be binary stars with active coronae. Extrapolating these optical identifications to the remaining unidentified X-ray source population, we estimate that 20-35 of the sources are CVs and a similar number are active binaries. This likely represents most of the CVs in the cluster, but only a small fraction of all the active binaries. We place a 2 sigma upper limit of L-x < 3 x 10(30) erg s(-1) on the integrated luminosity of any additional faint, unresolved population of sources in the core. We explore the significance of these findings in the context of primordial versus dynamical channels for CV formation. The number of CVs per unit mass in. Cen is at least 2-3 times lower than in the field, suggesting that primordial binaries that would otherwise lead to CVs are being destroyed in the cluster environment. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
globular clusters: individual (omega Centauri), binaries: close, cataclysmic variables, novae, stars: neutron, X-rays: binaries
in
Astrophysical Journal
volume
697
issue
1
pages
224 - 236
publisher
University of Chicago Press
external identifiers
  • wos:000265764000019
  • scopus:66649133445
ISSN
0004-637X
DOI
10.1088/0004-637X/697/1/224
language
English
LU publication?
yes
id
1d0eea04-6527-4e7f-b8f6-26a212b6c3ad (old id 1426461)
date added to LUP
2009-06-29 15:18:29
date last changed
2017-06-11 04:16:43
@article{1d0eea04-6527-4e7f-b8f6-26a212b6c3ad,
  abstract     = {We analyze a similar to 70 ks Chandra Advanced CCD Imaging Spectrometer exposure of the globular cluster omega Cen (NGC 5139). The similar to 17' x 17' field of view fully encompasses three core radii and almost twice the half-mass radius. We detect 180 sources to a limiting flux of similar to 4.3 x 10(-16) erg cm(-2) s(-1) (L-x = 1.2 x 10(30) erg s(-1) at 4.9 kpc). After accounting for the number of active galactic nuclei and possible foreground stars, we estimate that 45-70 of the sources are cluster members. Four of the X-ray sources have previously been identified as compact accreting binaries in the cluster-three cataclysmic variables (CVs) and one quiescent neutron star. Correlating the Chandra positions with known variable stars yields eight matches, of which five are probable cluster members that are likely to be binary stars with active coronae. Extrapolating these optical identifications to the remaining unidentified X-ray source population, we estimate that 20-35 of the sources are CVs and a similar number are active binaries. This likely represents most of the CVs in the cluster, but only a small fraction of all the active binaries. We place a 2 sigma upper limit of L-x &lt; 3 x 10(30) erg s(-1) on the integrated luminosity of any additional faint, unresolved population of sources in the core. We explore the significance of these findings in the context of primordial versus dynamical channels for CV formation. The number of CVs per unit mass in. Cen is at least 2-3 times lower than in the field, suggesting that primordial binaries that would otherwise lead to CVs are being destroyed in the cluster environment.},
  author       = {Haggard, Daryl and Cool, Adrienne M. and Davies, Melvyn B},
  issn         = {0004-637X},
  keyword      = {globular clusters: individual (omega Centauri),binaries: close,cataclysmic variables,novae,stars: neutron,X-rays: binaries},
  language     = {eng},
  number       = {1},
  pages        = {224--236},
  publisher    = {University of Chicago Press},
  series       = {Astrophysical Journal},
  title        = {A Chandra Study Of The Galactic Globular Cluster Omega Centauri},
  url          = {http://dx.doi.org/10.1088/0004-637X/697/1/224},
  volume       = {697},
  year         = {2009},
}