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J/ApJ/608/781       NGC 6530 Chandra X-ray catalog           (Damiani+, 2004)

A deep Chandra X-ray observation of the rich young cluster NGC 6530. I. The X-ray source catalog and the cluster population. Damiani F., Flaccomio E., Micela G., Sciortino S., Harnden F.R.Jr, Murray S.S. <Astrophys. J., 608, 781-796 (2004)> =2004ApJ...608..781D
ADC_Keywords: X-ray sources ; Clusters, open ; Stars, pre-main sequence Keywords: open clusters and associations: individual (NGC 6530) - stars: coronae - stars: pre-main-sequence - X-rays: stars Abstract: In a deep 60ks Chandra ACIS X-ray observation of the very young cluster NGC 6530, we detect 884 X-ray point sources and argue that a very large fraction of them (90%-95%) must be pre-main-sequence (PMS) cluster members, mostly of low masses. This is a significant enlargement of the known NGC 6530 stellar population with respect to previous optical studies, including Hα surveys. We identify 220 X-ray sources with catalogued stars down to V=17, while most unidentified sources have fainter counterparts. Moreover, we find an infrared counterpart in the 2MASS (II/246) catalog for 731 X-ray sources. The optically identified cluster X-ray sources are found in a band in the H-R diagram above the main sequence, in the locus of 0.5-1.5Myr PMS stars, with masses down to 0.5-1.5M. Description: NGC 6530 was observed for 60ks with the Chandra ACIS-I CCD detector on 2001 June 18-19 as part of the GTO program. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 141 901 NGC 6530 X-Ray Source Properties and Identifications
See also: II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) J/AJ/120/333 : UBVRI and Hα in NGC 6530 (Sung+, 2000) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 3 I3 --- [DFM2004] X-ray running number 5- 6 I2 h RAh Hour of Right Ascension (J2000.0) 8- 9 I2 min RAm Minute of Right Ascension (J2000.0) 11- 15 F5.2 s RAs Second of Right Ascension (J2000.0) 17 A1 --- DE- Sign of the Declination (J2000.0) 18- 19 I2 deg DEd Degree of Declination (J2000.0) 21- 22 I2 arcmin DEm Arcminute of Declination (J2000.0) 24- 27 F4.1 arcsec DEs Arcsecond of Declination (J2000.0) 29- 32 F4.2 arcsec e_Pos Position error 34- 40 F7.3 ct/ks CRate Count rate 42- 46 F5.3 ct/ks e_CRate Uncertainty in CRate 48- 53 F6.3 --- PK-S Kolmogorov-Smirnov test probability X-ray source is constant 55- 60 F6.3 --- HR1 ? First hardness ratio (1) 62- 67 F6.3 --- HR2 Second hardness ratio (2) 69- 71 I3 --- SCB ? Sung et al. (2000, Cat. J/AJ/120/333) number (Cl* NGC 6530 SCB NNNN in Simbad) 73- 77 F5.2 arcsec OffX-O ? X-ray and SCB optical positions offset 79- 84 F6.3 mag Vmag ? SCB V band magnitude 86- 91 F6.3 mag V-I ? SCB (V-I) color 93- 97 F5.3 mag B-V ? SCB (B-V) color 99-114 A16 --- 2MASS The 2MASS (Cat. II/246) designation 116-119 F4.2 arcsec OffX-IR ? X-ray and 2MASS positions offset 121-126 F6.3 mag Jmag ? 2MASS J band magnitude 128-133 F6.3 mag Hmag ? 2MASS H band magnitude 135-140 F6.3 mag Kmag ? 2MASS K band magnitude
Note (1): Defined as (H-S)/(H+S) where H and S are the source counts in two energy bands, here chosen as 0.75-1.5keV and 0.3-0.75keV. Note (2): Defined as (H-S)/(H+S) where H and S are the source counts in two energy bands, here chosen as 1.5-8.0keV and 0.75-1.5keV.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 14-Jun-2005
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