J/ApJ/598/375 Chandra X-ray observations of NGC 2024 (Skinner+, 2003)
A deep Chandra X-ray observation of the embedded young cluster in NGC 2024.
Skinner S., Gagne M., Belzer E.
<Astrophys. J., 598, 375-391 (2003)>
=2003ApJ...598..375S 2003ApJ...598..375S
ADC_Keywords: Associations, stellar ; Stars, pre-main sequence ; X-ray sources
Keywords: open clusters and associations: individual (NGC 2024) -
stars: formation - stars: pre-main-sequence - X-rays: stars
Abstract:
We present results of a sensitive 76ks Chandra observation of the
young stellar cluster in NGC 2024, lying at a distance of ∼415pc in
the Orion B giant molecular cloud. Previous infrared observations have
shown that this remarkable cluster contains several hundred embedded
young stars, most of which are still surrounded by circumstellar
disks. Thus, it presents a rare opportunity to study X-ray activity in
a large sample of optically invisible protostars and classical T Tauri
stars (CTTSs) undergoing accretion. Chandra detected 283 X-ray
sources, of which 248 were identified with counterparts at other
wavelengths, mostly in the near-infrared. Astrometric registration of
Chandra images against the Two Micron All Sky Survey (2MASS) resulted
in positional offsets of ∼0.25" near field center, yielding high
confidence identifications of infrared counterparts.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 155 283 CHANDRA X-ray Sources in NGC 2024
notes.dat 80 113 Notes
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See also:
B/chandra : The Chandra Archive Log (CXC, 2002)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- [SGB2003] Running object number
4- 5 A2 --- n_[SGB2003] [*f ] Note detailed in notes.dat file
7- 23 A17 --- Name Object name (JHHMMSS.s-DDMMSS)
25 I1 h RAh CHANDRA Right Ascension (J2000) (2)
27- 28 I2 min RAm CHANDRA Right Ascension (J2000) (2)
30- 34 F5.2 s RAs CHANDRA Right Ascension (J2000) (2)
36 A1 --- DE- CHANDRA Declination sign (J2000) (2)
37 I1 deg DEd CHANDRA Declination (J2000) (2)
39- 40 I2 arcmin DEm CHANDRA Declination (J2000) (2)
42- 45 F4.1 arcsec DEs CHANDRA Declination (J2000) (2)
47- 50 I4 ct NCts Net (0.5-7keV) counts (3)
52- 53 I2 ct e_NCts Uncertainty in NCts (4)
55- 59 F5.2 --- KS Kolmogorov-Smirnov variability
statistic (5)
61- 64 F4.2 keV E Mean (0.5-7keV) photon energy
66- 70 F5.2 10+22/cm2 NH ? Hydrogen absorption column density (6)
72- 76 F5.2 10+22/cm2 E_NH ? Upper 90% confidence error on NH (7)
78- 81 F4.2 10+22/cm2 e_NH ? Lower 90% confidence error on NH (7)
83- 85 F3.1 keV kT ? Characteristic plasma temperature (6)
87- 89 F3.1 keV E_kT ? Upper 90% confidence error on kT (7)
91- 93 F3.1 keV e_kT ? Lower 90% confidence error on kT (7)
95-102 E8.2 mW/m2 FX,abs The absorbed (0.5-7keV) flux in
units of erg/cm2/s (8)
104-108 F5.2 [10-7W] logLx ? Log of the (0.5-7keV) unabsorbed
luminosity in units of erg/s (9)
110 A1 --- f_logLx [v] Indicates a variable logLx
112-154 A43 --- ID Candidate IR, optical or radio
identification (10)
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Note (2): with astrometric correction applied.
Note (3): Net source counts = total counts - background counts. Source counts
were measured in PSF-corrected 95% encircled energy regions except
for the brightest sources where 99% encircled energy regions were
used; smaller regions were used for some closely-spaced sources.
Note (4): As described by Gehrels (1986ApJ...303..336G 1986ApJ...303..336G).
Note (5): Sources with KS>1.7 are variable (see text).
Note (6): Time-averaged values for sources with ≥90 counts as determined
from spectral fits with 1T VAPEC optically thin plasma model using
a fixed iron abundance Fe=0.3 solar (errors are 90% confidence).
Note (7): An upper or lower 90% confidence error of +0.0 or -0.0 is quoted
when the error calculation algorithm did not converge and no valid
90% confidence error was obtained.
Note (8): As determined from source event list (see text).
Note (9): At d=415pc as determined from spectral fits of brighter sources
where an estimate of NH and kT is available.
Note (10): From 2MASS, SIMBAD, and the following conventions:
B89-NN = Barnes et al. (1989ApJ...342..883B 1989ApJ...342..883B), [BCB89] IRS NN in Simbad
B-NN = Beck et al. (2003ApJ...583..358B 2003ApJ...583..358B), Cl* NGC 2024 BSC NN in Simbad
HLL-NNN = Haisch, Lada & Lada (2000AJ....120.1396H 2000AJ....120.1396H),
Cl* NGC 2024 HLL NNN in Simbad
HLP-NNN = Haisch et al. (2001AJ....121.1512H 2001AJ....121.1512H), Cl* NGC 2024 HLP NNN
M-NNN = Meyer (1996, Ph.D. thesis, Univ. Massachusetts, Amherst).
V-NN = Radio identifications from 3.6cm VLA observations of
Rodriguez et al. (2003ApJ...598.1100R 2003ApJ...598.1100R), [RGR2003] VLA NN in Simbad
HHMMSSss-DDMMSSs = IR identifications found in the all-sky release
of the 2MASS Point Source Catalog (II/246) are listed by
their coordinates (e.g. 05411324-0153306).
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Byte-by-byte Description of file: notes.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Note Note code
5- 80 A76 --- Text Text of the note
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 12-Jan-2004