J/A+A/490/641 X-ray sources toward NGC 2808 (Servillat+, 2008)
Combined Chandra, XMM-Newton, and Hubble Space Telescope observations of
the Galactic globular cluster NGC 2808.
Servillat M., Dieball A., Webb N.A., Knigge C., Cornelisse R., Barret D.,
Long K.S., Shara M.M., Zurek D.R.
<Astron. Astrophys., 490, 641-654 (2008)>
=2008A&A...490..641S 2008A&A...490..641S
ADC_Keywords: Clusters, globular ; X-ray sources ; Ultraviolet
Keywords: globular clusters: individual: NGC 2808 - X-rays: general -
binaries: close - novae, cataclysmic variables
Abstract:
Using new Chandra X-ray observations and existing XMM-Newton X-ray and
Hubble far ultraviolet observations, we aim to detect and identify the
faint X-ray sources belonging to the Galactic globular cluster
NGC 2808 in order to understand their role in the evolution of
globular clusters.
We present a Chandra X-ray observation of the Galactic globular
cluster NGC 2808. We classify the X-ray sources associated with the
cluster by analysing their colours and variability. Previous
observations with XMM-Newton and far ultraviolet observations with the
Hubble Space Telescope are re-investigated to help identify the
Chandra sources associated with the cluster. We compare our results to
population synthesis models and observations of other Galactic
globular clusters.
We detect 113 sources, of which 16 fall inside the half-mass radius of
NGC 2808 and are concentrated towards the cluster core.
Description:
NGC 2808 was observed with the Chandra X-ray Observatory and the
Chandra Advanced CCD Imaging Spectrometer-Imager (ACIS-I) at its focus
on 2007 June 19-21 (28 months after the XMM-Newton observation) for
two distinct exposures of 46 and 11 kiloseconds (ks).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 106 113 Detected Chandra sources in the direction
of NGC 2808
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-)
B/xmm : XMM-Newton Observation Log (XMM-Newton SOC, 2007)
J/A+AS/84/59 : Photometry of NGC 2808 (Ferraro+, 1990)
J/ApJ/562/368 : UV photometry in NGC 2808 (Brown+, 2001)
J/A+A/413/343 : RGB stars in NGC 2808 (Cacciari+, 2004)
J/ApJ/625/156 : FUV-NUV observations of NGC 2808 (Dieball+, 2005)
J/A+A/480/397 : XMM observations of NGC 2808 and NGC 4372 (Servillat+, 2008)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- [SDW2008] Sequential number
5 A1 --- Det [wh] Detection method (WAVDETECT or by hand)
7- 8 A2 --- XMM XMM-Newton ID (1)
10- 11 I2 h RAh Right ascension (J2000)
13- 14 I2 min RAm Right ascension (J2000)
16- 20 F5.2 s RAs Right ascension (J2000)
22 A1 --- DE- Declination sign (J2000)
23- 24 I2 deg DEd Declination (J2000)
26- 27 I2 arcmin DEm Declination (J2000)
29- 33 F5.2 arcsec DEs Declination (J2000)
35- 38 F4.2 arcsec Error 1sigma detection positional error
40- 42 I3 ct Cts Number of X-ray counts
44- 48 F5.2 10-17W/m2 FluxC Chandra flux (10-14erg/cm2/s)
50- 53 F4.2 10-17W/m2 e_FluxC rms uncertainty on Chandra flux
55- 59 F5.2 10-17W/m2 FluxX ?=- XMM flux (10-14erg/cm2/s)
61- 64 F4.2 10-17W/m2 e_FluxX ? rms uncertainty on XMM flux
66- 70 F5.2 --- HRC Chandra hardness ratio (2)
72- 75 F4.2 --- e_HRC rms uncertainty on Chandra hardness ratio
77- 81 F5.2 --- HRX ?=- XMM hardness ratio (2)
83- 86 F4.2 --- e_HRX ? rms uncertainty on XMM hardness ratio
88- 91 F4.2 10+22cm-2 NH [0.12] Absorption column density best fit
93- 97 F5.2 --- PH Power law of photon index best fit
99-106 E8.3 --- KS Kolmogorov-Smirnov probability of constancy
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Note (1): From Servillat et al., 2008, Cat. J/A+A/480/397,
[SWB2008] NGC 2808 NN or [SWB2008] NGC 2808 CN in Simbad,
Note (2): HR=(H-S)/(H+S), where
S is the count rate in the 0.5-2keV band and
H is the count rate in the 2-8keV band.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 23-Dec-2008