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J/ApJ/659/585   X-ray classification of young star clusters   (Hojnacki+, 2007)

An X-ray spectral classification algorithm with application to young stellar clusters. Hojnacki S.M., Kastner J.H., Micela G., Feigelson E.D., Lalonde S.M. <Astrophys. J., 659, 585-598 (2007)> =2007ApJ...659..585H
ADC_Keywords: Clusters, open ; X-ray sources Keywords: methods: statistical - open clusters and associations: general - stars: early-type - stars: pre-main-sequence - X-rays: stars Abstract: A large volume of low signal-to-noise, multidimensional data is available from the CCD imaging spectrometers aboard the Chandra X-Ray Observatory and the X-Ray Multimirror Mission (XMM-Newton). To make progress analyzing this data, it is essential to develop methods to sort, classify, and characterize the vast library of X-ray spectra in a nonparametric fashion (complementary to current parametric model fits). We have developed a spectral classification algorithm that handles large volumes of data and operates independently of the requirement of spectral model fits. We use proven multivariate statistical techniques including principal component analysis and an ensemble classifier consisting of agglomerative hierarchical clustering and K-means clustering applied for the first time for spectral classification. The algorithm positions the sources in a multidimensional spectral sequence and then groups the ordered sources into clusters based on their spectra. These clusters appear more distinct for sources with harder observed spectra. The apparent diversity of source spectra is reduced to a three-dimensional locus in principal component space, with spectral outliers falling outside this locus. The algorithm was applied to a sample of 444 strong sources selected from the 1616 X-ray emitting sources detected in deep Chandra imaging spectroscopy of the Orion Nebula Cluster. Description: Data from the COUP (Getman et al., 2005, Cat. J/ApJS/160/319) observations (ObsIDs 4395, 3744, 4373, 4374, 4396, and 3498) of the ONC were used as the input data set for development of the X-ray source classification algorithm. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 77 444 Properties of the 444 COUP sources
See also: J/ApJS/160/319 : COUP: observations and source lists (Getman+, 2005) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 4 I4 --- COUP COUP source number (1) 6- 7 I2 --- Class [1-17] X-ray spectral class (see paper) 9- 14 F6.2 --- HR2 ? Hardness ratio 2 (0.5-1.7 vs. 1.7-2.8keV) (1) 16- 21 F6.2 --- HR3 Hardness ratio 3 (1.7-2.8 vs. 2.8-8.0keV) (1) 23- 28 F6.2 [cm-2] NH Log Hydrogen column density (1) 30- 35 F6.2 keV kT1 Energy of first plasma component (1) 37- 42 F6.2 keV kT2 ? Energy of second plasma component (1) 44- 49 F6.2 --- T1/T2 ? Ratio of first and second plasma components 51- 56 F6.3 [K] Teff ? Log of the stellar effective temperature (1) 58- 63 F6.1 0.1nm EWCa ? Equivalent width of CaII line in Angstroms (1) 65- 70 F6.2 mag AV ? The visual absorption (1) 72- 77 F6.2 mag DelK ? The Delta(I-K) near-infrared excess (1)
Note (1): From Getman et al. (2005, Cat. J/ApJS/160/319).
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 25-Jan-2009
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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