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IC348CXO2 - IC 348 Chandra X-Ray Point Source Catalog 2

 HEASARC
Archive

Overview

IC 348 is a nearby (~ 310 pc), young (~ 2 - 3 Myr) open cluster with > 300 members identified from optical and infrared observations. The authors studied the properties of the coronae of the young low-mass stars in IC 348, combining X-ray and optical/infrared data. The four existing Chandra observations of IC 348 were merged, thus providing a deeper and spatially more complete X-ray view than previous X-ray studies of the cluster. The authors compiled a comprehensive catalog of IC 348 members taking into account recent updates to the cluster census. Their data collection comprises fundamental stellar parameters, infrared excess indicating the presence of disks, H-alpha emission as a tracer of chromospheric emission or accretion, and mass accretion rates. The authors have detected 290 X-ray sources in four merged Chandra exposures, of which 185 are associated with known cluster members corresponding to a detection rate of ~ 60% for the cluster members of IC 348 identified in optical/infrared studies. According to the most recent spectral classification of IC 348 members, only four of the X-ray sources are brown dwarfs (spectral type M6 and later). The detection rate is highest for diskless Class III stars and increases with stellar mass. This may be explained with higher X-ray luminosities for higher mass and later evolutionary stage that is evident in the X-ray luminosity functions. In particular, the authors find that for the lowest examined masses (0.1 Msun - 0.25 Msun) there is a difference between the X-ray luminosity functions of accreting and non-accreting stars (classified on the basis of their H-alpha emission strength) as well as those of disk-bearing and diskless stars (classified on the basis of the slope of the spectral energy distribution). These differences disappear for higher masses. This is related to the finding that the Lx/Lbol ratio is non-constant across the mass/luminosity sequence of IC 348 with a decrease towards lower luminosity stars. Their analysis of an analogous stellar sample in the Orion Nebula Cluster suggests to the authors that the decline of Lx/Lbol for young stars at the low-mass end of the stellar sequence is likely universal.

X-ray fluxes are presented for all (185) known optical/infrared IC348 members which were observed and detected by Chandra. The basic source parameters for all X-ray sources, i.e., including an additional 105 sources not associated with known IC 348 members, are given. The X-ray flux upper limits for 129 IC 348 members which were observed but not detected by Chandra (present in the as published version of Table 3 from the reference paper) are not included in this HEASARC representation of the data given in Tables 3 and 7 from the reference paper. Thus, this table contains 290 (185 + 105) rows, one for each X-ray source (IC 348 member or not) detected by Chandra in the direction of IC 348.

Catalog Bibcode

2012A&A...537A.135S

References

X-ray view of IC348 in the light of an updated cluster census.
    Stelzer B., Preibisch T., Alexander F., Mucciarelli P., Flaccomio E.,
    Micela G., Sciortino S.
    <Astron. Astrophys. 537, A135 (2012)>
    =2012A&A...537A.135S        (SIMBAD/NED BibCode)

Provenance

This HEASARC table was created in February 2012 based on CDS Catalog J/A+A/537/A135 files table3.dat and table7.dat. It lists the X-ray counts and other properties for the 290 Chandra X-ray sources which were listed in table7.dat. It does not include the X-ray flux upper limits for 129 non-detected IC 348 members which were given in table3.dat, so only the X-ray fluxes and luminosities for the 185 X-ray detected IC 348 members given in table3.dat are included in this table. Notice that in the CDS version there were 2 duplicate entries in table3.dat.

Parameters

Source_Number
A unique identification number for each X-ray source in the catalog, in order of increasing J2000.0 Right Ascension.

Name
The Chandra X-ray source designation, in the form recommended by the Dictionary of Nomenclature of Celestial Objects for unregistered Chandra sources based on their truncated J2000.0 equatorial coordinates, viz., 'CXOU JHHMMSS.s+DDMMSS'. In the reference paper, the authors used names with higher precision, i.e., 'CXOU JHHMMSS.ss+DDMMSS.s' which the HEASARC shortened accordingly after verifying that no duplicate names resulted.

RA
The Right Ascension of the Chandra source in the selected equinox. This was given in J2000.0 equatorial coordinates in decimal degrees to a precision of 10-6 degrees in the original table.

Dec
The Declination of the Chandra source in the selected equinox. This was given in J2000.0 equatorial coordinates in decimal degrees to a precision of 10-6 degrees in the original table.

LII
The Galactic Longitude of the Chandra source.

BII
The Galactic Latitude of the Chandra source.

Error_Radius
The estimated standard deviation of the random component of the position error, sqrt (sigma(x)2 + sigma(y)2) of the Chandra source, in arcseconds. The single-axis position errors, sigma(x) and sigma(y), are estimated from the single-axis standard deviations of the PSF inside the extraction region and the number of counts extracted.

Off_Axis
The off-axis angle of the Chandra source from the nominal pointing direction, in arcminutes.

Counts
The net counts extracted for the Chandra source in the total energy band (0.5 - 8.0 keV).

Counts_Error
The 1-sigma uncertainty (the average of the upper and lower errors) for the net source counts extracted in the total energy band.

Bck_Counts
The background counts expected in the Chandra source extraction region in the total energy band.

HB_Counts
The net counts extracted for the Chandra source in the hard energy band (2.0 - 8.0 keV).

PSF_Fraction
The fraction of the PSF which is enclosed within the extraction region (at 1.497 keV). Note that a reduced PSF fraction (significantly below 90%) may indicate that the source is in a crowded region or on the edge of the field.

SNR
The photometric significance of the Chandra source computed as the net counts divided by the upper error in the net counts.

Log_Bck_Prob_Limit
This flag is set to '<' if the corresponding parameter value is an upper limit.

Log_Bck_Prob
The logarithm of the probability Pb that the observed counts (in the total band) are solely from a background fluctuation rather than from a real source. Some sources have Pb values above the 0.1% threshold that defines the catalog because local background estimates can rise during the final extraction iteration after sources are removed from the catalog.

Source_Anomaly_Flag
This parameter contains a source anomalies flag which is set to 'g' if the fractional time that the source was on a detector (the FRACEXPO value from mkarf) is < 0.9.

Source_Variable_Flag
This parameter contains flag values which can be set to to the following values indicative of the presence or absence of source variability based on the Kolmogorov-Smirnov (K-S) statistic (no value is reported for sources with fewer than four counts or for sources in chip gaps or on field edges): 

             a = no evidence for variability (0.05 < PKS)
             b = possibly variable (0.005 < PKS < 0.05)
             c = definitely variable (PKS < 0.005)

Exposure
The effective exposure time for the Chandra source, in seconds. This is the approximate time that the source would have to have been observed at the aimpoint of the Chandra ACIS-I detector to obtain the same number of counts that were actually obtained at its position in the focal plane.

Median_Energy
The background-corrected median photon energy for the Chandra source over the total 0.5 - 8 keV energy band, in keV.

Cluster_Number
The source identifier for members of the IC 348 cluster. If the object is not a known cluster member, this parameter is left blank. To construct a name for the cluster members which is recognized by the Simbad name resolver, the user should add the prefix of 'Cl* IC 348 LRL ' (for Luhman, Rieke, Lada+ 1998 ApJ, 508, 347 who began numbering members of IC 348) to the cluster number value, e.g., Cl* IC 348 LRL 2' for the source with cluster number = 2.

Flux
The X-ray flux of the Chandra source, in erg s-1 cm-2, presumably in the total 0.5-8.0 keV energy band. This is either (1) the intrinsic, i.e., extinction-corrected, X-ray flux of the Chandra source obtained using the XPHOT software (for those sources for which the flux_flag parameter is blank) or (2) the observed, i.e., not the intrinsic, X-ray flux of the Chandra source (called FLUX2 by the authors) which is computed by the AE software from the product of the photon flux and the median photon energy (for those sources which are too faint to perform the XPHOT analysis on and for which the flux_flag parameter is set to to 'f2').

Log_Lx
The logarithm of the X-ray luminosity of the Chandra source, in erg s-1. This is given only for those 187 sources which are known to be associated with cluster members, else it is left blank. The HEASARC created this parameter using the X-ray flux values which were provided and assuming a distance of 310 pc to the cluster. If flux_flag is blank, the luminosity is the intrinsic, extinction-corrected, luminosity, whereas if flux_flag is 'f2', it is the observed luminosity and may be significantly less than the intrinsic luminosity if there is significant extinction towards the source.

Flux_Flag
This prameter flag indicates the type of flux quoted for the Chandra source: a blank value means that the flux is the intrinsic, i.e., extinction-corrected, X-ray flux of the Chandra source obtained using the XPHOT software, while a value of 'f2' means it is the observed, i.e., not the intrinsic, X-ray flux of the Chandra source (called FLUX2 by the authors) which is computed by the AE software from the product of the photon flux and the median photon energy.

Contact Person

Questions regarding the IC348CXO2 database table can be addressed to the HEASARC User Hotline.

A service of the Astrophysics Science Division at NASA/GSFC and the High Energy Astrophysics Division of the Smithsonian Astrophysics Observatory (SAO)

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Last Modified: 6-Feb-2012