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J/A+A/533/A121     Missing low-mass stars in S254-S258      (Mucciarelli+, 2011)

Revealing the "missing" low-mass stars in the S254-S258 star forming region by deep X-ray imaging. Mucciarelli P., Preibisch T., Zinnecker H. <Astron. Astrophys. 533, A121 (2011)> =2011A&A...533A.121M
ADC_Keywords: Stars, pre-main sequence ; YSOs ; Protostars ; X-ray sources Keywords: stars, formation - stars: pre-main-sequence - open clusters and associations: individual: individual: S254-S258 - X-ray: stars Abstract: The aim of this study was to find an explanation for the remarkable morphology of the central part of the S254-S258 star forming complex. We performed a deep Chandra X-ray observation of the S254-S258 region in order to efficiently discriminate young stars (with and without circumstellar matter) from the numerous older field stars in the area. We detected 364 X-ray point sources in a 17'x17' field. This X-ray catalog provides, for the first time, a complete sample of all young stars in the region down to about 0.5M. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 106 364 Chandra catalog: basic source properties table3.dat 54 364 *X-ray fluxes and luminosities of the Chandra sources for an assumed distance of 1.6kpc table5.dat 34 364 Cross-correlation of the X-ray sources with optical and IR catalogs
Note on table3.dat: X-ray luminosities obtained with the XPHOT software (Getman et al., see; these luminosities may differ from the luminosities derived from spectral analysis in table4 of paper (see sections 3.1.2 and 3.1.3 of the paper)
See also: II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) J/ApJ/682/445 : Spitzer observations of S254-S258 (Chavarria+, 2008) B/chandra : The Chandra Archive Log (CXC, 1999-) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 3 I3 --- Seq X-ray catalog sequence number, sorted by RA. 5- 22 A18 --- CXOU IAU J designation ( 24- 32 F9.6 deg RAdeg Right ascension in decimal degrees (J2000) 34- 42 F9.6 deg DEdeg Declination in decimal degrees (J2000) 44- 46 F3.1 arcsec ePos Estimated standard deviation of the random component of the position error (1) 48- 51 F4.1 arcmin theta Off-axis angle 53- 57 F5.1 ct Ct Net counts extracted in the total energy band (0.5-8keV) 59- 62 F4.1 ct e_Ct Average of upper and lower 1σ errors 64- 68 F5.1 ct Background counts expected in the source extraction region (total band) 70- 74 F5.1 ct Ct.h Net counts extracted in the hard energy band (2-8keV) 76- 79 F4.2 --- f.PSF Fraction of the PSF (at 1.497keV) enclosed within the extraction region (2) 81- 84 F4.1 --- Signi Photometric significance computed as net counts divided by the upper error on net counts 86 A1 --- l_logPb Limit flag on logPb 87- 90 F4.1 --- logPb Logarithmic probability that extracted counts (total band) are solely from background (3) 92 A1 --- Anom [geps ] Source anomalies (only 'g' present) (4) 97 A1 --- Var [abc] Variability characterization based on K-S statistic (c=variable, total band) (5) 99-102 F4.1 ks Texp Effective exposure time (6) 104-106 F3.1 keV Emed Background-corrected median photon energy (total band)
Note (1): sqrt(σx2y2). The single-axis position errors, σx and σy, are estimated from the single-axis standard deviations of the PSF inside the extraction region and the number of counts extracted. Note (2): A reduced PSF fraction (significantly below 90%) may indicate that the source is in a crowded region. Note (3): Some sources have PB values above the 1% threshold that defines the catalog because local background estimates can rise during the final extraction iteration after sources are removed from the catalog. Note (4): Source anomalies as follows: g = fractional time that source was on a detector is <0.9 e = source on field edge p = source piled up s = source on readout streak Note (5): Variability code as follows: a = no evidence for variability (0.05<PKS) b = possibly variable (0.005<PKS<0.05) c = definitely variable (PKS<0.005) - = No value is reported for sources with fewer than four counts or for sources in chip gaps or on field edges. Note (6): Approximate time the source would have to be observed at the aimpoint of the ACIS-I detector in Cycle 11 to obtain the reported number of net counts.
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 3 I3 --- Seq X-ray catalog sequence number, sorted by RA. 4 A1 --- n_Seq [*] indicates brighter sources having spectral fit (slightly different) in table 4 of paper 6- 23 A18 --- CXOU IAU J designation ( 25- 30 F6.3 ph/cm2/s Flux2 Incident full band [0.5-8.0]keV flux from AE software, calculated using the scalar mean of the ancillary response function (ARF) 32- 36 F5.2 [10-7W] logLh ?=- Apparent hard band [2.0-8.0]keV luminosity 38- 42 F5.2 [10-7W] logLhc ?=- Intrinsic hard band [2.0-8.0]keV luminosity (corrected for absorption) 44- 48 F5.2 [10-7W] logLt ?=- Apparent full band [0.5-8.0]keV luminosity 50- 54 F5.2 [10-7W] logLtc ?=- Intrinsic full band [0.5-8.0]keV luminosity
Byte-by-byte Description of file: table5.dat
Bytes Format Units Label Explanations
1- 3 I3 --- Seq X-ray catalog sequence number, sorted by RA. 5- 22 A18 --- CXOU CXOU J designation ( 24 A1 --- DSS [y-] Optical counterpart in at least the DSS red image 26- 28 A3 --- 2M [JHK-] Counterpart in the 2MASS catalog in the J, H or K band 30 A1 --- C08 [y-] Counterpart in the Spitzer catalog from Chavarria et al. (2008, Cat. J/ApJ/682/445) 32- 34 A3 --- Class IR classification is reported when available (7)
Note (7): Infrared classes are only reported for those sources where the closest match in the Chavarria et al. (2008, Cat. J/ApJ/682/445) catalog has a known infrared class.
Acknowledgements: P. Mucciarelli, pmuccia(at)
(End) Patricia Vannier [CDS] 14-Jun-2011
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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