J/ApJ/697/224 Chandra X-ray sources in ω Cen (Haggard+, 2009)
A Chandra study of the Galactic globular cluster omega Centauri.
Haggard D., Cool A.M., Davies M.B.
<Astrophys. J., 697, 224-236 (2009)>
=2009ApJ...697..224H 2009ApJ...697..224H
ADC_Keywords: Clusters, globular ; X-ray sources ; Cross identifications
Keywords: binaries: close - globular clusters: individual (ω Centauri) -
novae, cataclysmic variables - stars: neutron - X-rays: binaries
Abstract:
We analyze a ∼70ks Chandra Advanced CCD Imaging Spectrometer exposure
of the globular cluster ω Cen (NGC 5139). The ∼17'x17' field of
view fully encompasses three core radii and almost twice the half-mass
radius. We detect 180 sources to a limiting flux of
∼4.3x10-16erg/cm2/s (Lx=1.2x1030erg/s at 4.9kpc). 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.
Description:
We obtained two exposures of ω Cen using the imaging array of the
Advanced CCD Imaging Spectrometer (ACIS-I) on 2000 January 24-25, in
"very faint" mode. The total exposure time was 72.4ks.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 113 180 ω Cen X-ray sources
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-)
J/ApJ/663/1021 : Log of ω Cen scientific images (Castellani+, 2007)
J/A+A/424/1101 : Variable Stars in the field of ω Cen (Kaluzny+, 2004)
J/A+A/400/521 : Omega Cen XMM observations (Gendre+, 2003)
J/ApJ/578/405 : Neutron stars in NGC 5139 (Rutledge+, 2002)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- ID Source identification in this work
6- 24 A19 --- CXOHCD IAU name (JHHMMSS.ss+DDMMSS.s)
26- 29 F4.2 --- Offset Radial offset from the cluster center in units
of core radii
31- 33 I3 ct Mcts Medium band raw source counts (0.5-4.5keV)
35- 39 F5.1 ct Mctsc Medium band corrected source counts (0.5-4.5keV)
41- 43 I3 ct Scts Soft band raw source counts (0.5-1.5keV)
45- 49 F5.1 ct Sctsc Soft band corrected source counts (0.5-1.5keV)
51- 53 I3 ct Hcts Hard band raw source counts (1.5-6.0keV)
55- 59 F5.1 ct Hctsc Hard band corrected source counts (1.5-6.0keV)
61- 63 I3 ct Cts Raw X-ray counts in the Chandra Deep Field South
(CDFS) soft X-ray band (0.5-2.0keV)
65- 69 F5.1 ct Ctsc Corrected X-ray counts in the Chandra Deep Field
South (CDFS) soft X-ray band (0.5-2.0keV)
71- 76 F6.3 --- S/H ? Hardness ratio
78- 84 E7.2 mW/m2 Fx X-ray flux derived from the medium counts values
86-104 A19 --- OName Previous X-ray ID references (1)
105-113 A9 --- OptID Optical ID (2)
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Note (1): X-ray ID references abbreviations are:
PSPC = Johnston et al. 1994A&A...289..763J 1994A&A...289..763J (<[JVH94] NGC 5139 NN> in Simbad)
HRI = Verbunt & Johnston, 2000A&A...358..910V 2000A&A...358..910V
(<[JVH94] NGC 5139 NNa> in Simbad)
ACIS = Rutledge et al. 2002, Cat. J/ApJ/578/405 (<[RBB2002b] NN> in Simbad)
XMM = Gendre et al. 2003, Cat. J/A+A/400/521 (<[GBW2003] NNN> in Simbad)
Note (2): Optical ID references abbreviations are:
HD = Hog et al. 1998, Cat. I/250; Perryman et al. 1997, Cat. I/239;
CV = Carson et al. 2000ApJ...532..461C 2000ApJ...532..461C, Haggard et al. 2002AAS...201.0718H 2002AAS...201.0718H,
2003AAS...203.5203H 2003AAS...203.5203H;
qNS = Haggard et al. 2004ApJ...613..512H 2004ApJ...613..512H;
V,NV = Kaluzny et al. 2004, Cat. J/A+A/424/1101
(<Cl* NGC 5139 SAW VNNN> in Simbad)
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 18-May-2011