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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
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:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 155 283 CHANDRA X-ray Sources in NGC 2024 notes.dat 80 113 Notes
See also: B/chandra : The Chandra Archive Log (CXC, 2002) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
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)
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). 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), [BCB89] IRS NN in Simbad B-NN = Beck et al. (2003ApJ...583..358B), Cl* NGC 2024 BSC NN in Simbad HLL-NNN = Haisch, Lada & Lada (2000AJ....120.1396H), Cl* NGC 2024 HLL NNN in Simbad HLP-NNN = Haisch et al. (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), [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).
Byte-by-byte Description of file: notes.dat
Bytes Format Units Label Explanations
1- 3 A3 --- Note Note code 5- 80 A76 --- Text Text of the note
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 12-Jan-2004
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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