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J/ApJ/582/382   Chandra X-ray sources in Orion Nebula Cluster (Flaccomio+, 2003)

Chandra X-ray observation of the Orion Nebula Cluster. I. Detection, identification, and determination of X-ray luminosities. Flaccomio E., Damiani F., Micela G., Sciortino S., Harnden F.R.Jr, Murray S.S., Wolk S.J. <Astrophys. J. 582, 382 (2003)> =2003ApJ...582..382F
ADC_Keywords: Clusters, open ; X-ray sources Mission_Name: Chandra Keywords: open clusters and associations: individual (Orion Nebula Cluster) - X-rays: stars Abstract: In this first of two companion papers on the Orion Nebula Cluster (ONC), we present our analysis of a 63ks Chandra HRC-I observation that yielded 742 X-ray detections within the 30'x30' field of view. To facilitate our interpretation of the X-ray image, here we collect a multiwavelength catalog of nearly 2900 known objects in the region by combining 17 different catalogs from the recent literature. We define two reference groups: an infrared sample, containing all objects detected in the K band, and an optical sample comprising low-extinction, well-characterized ONC members. We show for both samples that field object contamination is generally low. Our X-ray sources are primarily low-mass ONC members. The detection rate for optical sample stars increases monotonically with stellar mass from zero at the brown dwarf limit to ∼100% for the most massive stars but shows a pronounced dip between 2 and 10M. We determine LX and LX/Lbol or all stars in our optical sample and utilize this information in our companion paper to study correlations between X-ray activity and other stellar parameters. Description: We assembled an extensive catalog of known X-ray/optical/IR and radio objects that fell within the HRC FOV. In addition to our list of HRC sources and the Chandra source lists of Garmire et al. (2000, Cat. J/AJ/120/1426) and Schulz et al. (2001, Cat. J/ApJ/549/441), we considered 14 catalogs from recent publications, producing a database of nearly 2900 distinct objects reported in at least one of the studies considered. A full list of references is given in the first column of Table 2 along with a concise classification of the work and the referenced table number(s) from the original work. The HRC on board the Chandra X-Ray Observatory (Weisskopf et al., 2002PASP..114....1W) observed the ONC for 63.2ks on 2000 February 4. The pointing (R.A. = 5h 35m 17s, DE=-5° 23' 16" (J2000.0)) was chosen to place the Trapezium region and the bright O star θ1 Ori C in the center of the field of view (FOV). A good fraction of the ONC region was included in the 30'x30' HRC FOV. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 64 742 X-ray sources detected in the Orion Nebula Cluster table2.dat 119 18 List of Catalogs in the ONC Area table4.dat 78 696 Catalog of the ONC optical sample
See also: J/AJ/113/1733 : Orion Nebula Cluster population (Hillenbrand 1997) J/AJ/120/1426 : Chandra sources in ONC + BN-KL (Garmire+, 2000) J/AJ/125/1537 : QUIRC Chandra sources in OMC 2/3 (Tsujimoto+, 2003) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 3 I3 --- Xseq X-ray source number ([FDM2003] X NNN in Simbad) 5 I1 h RAh Source hour of Right Ascension (J2000) 7- 8 I2 min RAm Source minute of Right Ascension (J2000) 10- 14 F5.2 s RAs Source second of Right Ascension (J2000) 16 A1 --- DE- Sign of the Declination (J2000) 17 I1 deg DEd Source degree of Declination (J2000) 19- 20 I2 arcmin DEm Source arcminute of Declination (J2000) 22- 26 F5.2 arcsec DEs Source arcsecond of Declination (J2000) 28- 31 F4.2 arcsec e_Pos Statistical uncertainty in RA and DE 33- 38 F6.2 --- S/N Detection signal-to-noise ratio 40- 48 F9.2 ct Cts X-ray counts 50- 55 F6.2 ct e_Cts Uncertainty in Cts 57- 62 F6.2 ks Exp Effective exposure time (1)
Note (1): Derived from an exposure map calculated with CIAO for an incident energy of 2.0keV.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 45 A45 --- Ref Reference 47- 66 A20 --- Study Type of study 68- 71 A4 --- Tablea Number of the table in the original publication 72- 75 I4 --- Number Number of sources in the HRC field of view 77- 79 F3.1 arcsec R95 ? The 95% quantiles of the object distances from the Jones & Walker 1988AJ.....95.1755J counterparts. 81- 84 I4 --- NR ? Number of objects used to derive R95, i.e., identified with Jones & Walker 1988AJ.....95.1755J 86- 88 I3 --- NHRC ? Number of objects identified with an HRC X-ray source 90-119 A30 --- Data Data collected from each catalog; superscripts give precedence for acceptance in our catalog
Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
1- 3 I3 --- Oseq Reference number ([FDM2003] Opt NNN in Simbad) 5 I1 h RAh Hour of Right Ascension (J2000) 7- 8 I2 min RAm Minute of Right Ascension (J2000) 10- 14 F5.2 s RAs Second of Right Ascension (J2000) 16 A1 --- DE- Sign of the Declination (J2000) 17 I1 deg DEd Degree of Declination (J2000) 19- 20 I2 arcmin DEm Arcminute of Declination (J2000) 22- 26 F5.2 arcsec DEs Arcsecond of Declination (J2000) 28- 32 F5.2 solMass Mass Mass 34- 37 F4.2 [yr] logAge ? Log of the Age 39- 43 F5.2 d Prot ? Rotation period 45- 50 F6.2 0.1nm EW ? Ca II 8542Å equivalent width (1) 52 A1 --- l_CRate Limit flag on CRate 54- 60 F7.2 ct/ks CRate Basal HRC Count Rate 62 A1 --- l_logXLum Limit flag on XLum 64- 68 F5.2 [10-7W] logXLum Log of the X-ray luminosity 70 A1 --- l_logX/bol Limit flag on X/bol 72- 76 F5.2 [-] logX/bol ? Log of the X-ray to bolometric luminosity ratio
Note (1): Negative values indicate emission.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 21-Feb-2003
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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