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 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:
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FileName Lrecl Records Explanations
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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
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Note on table3.dat: X-ray luminosities obtained with the XPHOT software
(Getman et al., see http://www.astro.psu.edu/users/gkosta/XPHOT/); 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)
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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
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq X-ray catalog sequence number, sorted by RA.
5- 22 A18 --- CXOU IAU J designation (HHMMSS.ss+DDMMSS.s)
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 Ct.bg 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)
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Note (1): sqrt(σx2+σy2). 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.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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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 (HHMMSS.ss+DDMMSS.s)
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
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq X-ray catalog sequence number, sorted by RA.
5- 22 A18 --- CXOU CXOU J designation (HHMMSS.ss+DDMMSS.s)
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)
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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.
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Acknowledgements:
P. Mucciarelli, pmuccia(at)usm.uni-muenchen.de
(End) Patricia Vannier [CDS] 14-Jun-2011