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 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 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:
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FileName Lrecl Records Explanations
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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
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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
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Bytes Format Units Label Explanations
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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)
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Note (1): Derived from an exposure map calculated with CIAO
for an incident energy of 2.0keV.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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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 1988AJ.....95.1755J
counterparts.
81- 84 I4 --- NR ? Number of objects used to derive R95, i.e.,
identified with Jones & Walker
1988AJ.....95.1755J 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
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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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
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Note (1): Negative values indicate emission.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 21-Feb-2003