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CHAINTHCXO - Chamaeleon I North Cloud Chandra X-Ray Point Source Catalog

HEASARC
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Overview

This table contains the Chamaeleon (Cha) I North Cloud Chandra X-Ray point source catalog. Sensitive X-ray imaging surveys provide a new and effective tool to establish the census of pre-main-sequence (PMS) stars in nearby young stellar clusters. A deep Chandra X-Ray Observatory (CXO) observation of PMS stars in the Chamaeleon I North cloud achieved a limiting total-band X-ray luminosity of log L_t ~ 10^27 ergs/s (0.5 - 8 keV band) in a 0.8 x 0.8 pc^2 region. Of the 107 X-ray sources, 37 are associated with Galactic stars, of which 27 are previously recognized cloud members. These include 3 PMS brown dwarfs: the protostellar brown dwarf ISO 192 has a particularly high level of magnetic activity. Follow-up optical photometry and spectroscopy establish that 9-10 of the Chandra sources are probably magnetically active background stars. No new X-ray-discovered stars were confidently found despite the high sensitivity of the Chandra observation. From these findings, the authors argue that the sample of 27 PMS cloud members in the Chandra field is uncontaminated and complete down to K = 12 or a stellar mass of about 0.1 solar masses.

A 16'x 16' region of the Cha I North cloud was observed with the imaging array of the Advanced CCD Imaging Spectrometer (ACIS-I) detector on board the Chandra X-Ray Observatory. The observation took place on 2001 July 2.25-3.04 UT with the detector aimpoint set at 11 10 00.0, -76 35 00 (J2000.0 RA and Declination). The effective exposure was 66.3 ksec. The authors also obtained VI-band CCD images of most of the ACIS field with the 1m telescope and CCD detector at the South African Astronomical Observatory (SAAO) during 2002 February.


Catalog Bibcode

2004ApJ...614..267F

References

An X-ray census of young stars in the Chamaeleon I North cloud.
    Feigelson E.D., Lawson W.A.
   <Astrophys. J., 614, 267-283 (2004)>
   =2004ApJ...614..267F    (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in February 2007 based on CDS catalog J/ApJ/614/267 files table1.dat, table2.dat and table3.dat.

Parameters

Source_Number
A running X-ray source number in order of increasing J2000.0 Right Ascension.

Name
The name for the catalogued X-ray source based on the '[FL2004]' prefix (for Feigelson and Lawson 2004) and the source number, as recommended by the CDS Dictionary of Nomenclature of Celestial Objects.

Note_Flag
This flag parameter is set to 'a' for source number 105, since it lies at the edge of the ACIS detector where, because of the broad telescope PSF and satellite dithering, many of the source photons may have been lost, which can result in an underestimate of the source luminosity and an apparent positional offset of the centroid.

RA
The Right Ascension of the X-ray source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.1 seconds of time in the original table. The X-ray positions were derived from the ACIS image aligned to 2MASS sources. Generally, positions are accurate to less than 0.3" for values of the off-axis angle theta < 5' and more than 100 counts. Positional accuracy degrades to ~1" for fainter on-axis sources and to 2" - 3" for sources far off-axis (theta > 10').

Dec
The Declination of the X-ray source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.1 arcseconds in the original table. The X-ray positions were derived from the ACIS image aligned to 2MASS sources. Generally, positions are accurate to less than 0.3" for values of the off-axis angle theta < 5' and more than 100 counts. Positional accuracy degrades to ~1" for fainter on-axis sources and to 2" - 3" for sources far off-axis (theta > 10').

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Off_Axis
The off-axis angle theta of the X-ray source, in arcminutes.

Counts
The 0.5-8.0 keV events extracted from the 95% enclosed-energy polygon after subtracting background and rounding to the nearest integer obtained from acis_extract, in counts.

Chxr_Number
The ROSAT source number CHRX from the study of Feigelson et al. (1993ApJ...416..623F) which corresponds to the Chandra X-ray source.

Alt_Name
The proposed stellar counterpart to the X-ray source. The name comes from the cloud membership list of Carpenter et al. (2002, CDS Cat. <J/AJ/124/1001>). "Field" indicates previously unremarked stellar counterparts. The remainder of the X-ray sources lacking stellar conterparts are probably extragalactic.

Offset
The offset between the Chandra and 2MASS positions, in arcseconds.

Gross_Counts
The gross counts in the X-ray source from the extraction region. This parameter is provided only for the Chandra X-ray sources with stellar counterparts. The extraction analysis was done using acis_extract, version 1.1: for more details, see http://www.astro.psu.edu/xray/docs/TARA/ae_users_guide.html .

Bck_Counts
The background counts scaled to the extraction region size used for the X-ray source. This parameter is provided only for the Chandra X-ray sources with stellar counterparts. The extraction analysis was done using acis_extract, version 1.1: for more details, see http://www.astro.psu.edu/xray/docs/TARA/ae_users_guide.html .

Variability_Flag
This flag parameter contains a code with information on the variability or constancy of the X-ray source based on the variability probability P_KS obtained from the Kolmogorov-Smirnov Test that the source has no significant variation during the exposure. This parameter is provided only for the Chandra X-ray sources with stellar counterparts. The variability analysis based on the arrival times of the extracted events was made using acis_extract, version 1.1: for more details, see the document at http://www.astro.psu.edu/xray/docs/TARA/ae_users_guide.html . P_KS is coded to the probability from the Kolmogorov-Smirnov test as follows:

    a means P_KS > 0.05 (i.e., no evidence for variability)
    b means 0.005 > P_KS > 0.05 (i.e., possibly variable)
    c means P_KS < 0.005 (i.e., definitely variable)
  

Log_NH
The logarithm of the equivalent Hydrogen column density, in atoms cm^-2, assuming solar metallicities in the intervening gas, as obtained from the best-fit spectral model to the X-ray source events. The spectral modeling was done using XSPEC, version 11.2. This parameter is provided only for the Chandra X-ray sources with stellar counterparts.

Log_NH_Flag
This flag is set to ':' to indicates that there is an uncertainty in the corresponding Hydrogen column density.

Te_Plasma_1
The plasma temperature of the best-fit Mewe and Kaastra (single or lower-temperature) plasma component, in keV. This parameter is provided only for those Chandra X-ray sources which have stellar counterparts. The spectral modeling was done using XSPEC, version 11.2, and involved fitting the observed events with either a one-temperature (1T) plasma, or two- or three-temperature (2T or 3T) plasmas. Weak sources (typically < 100 counts) are successfully modeled with 1T plasmas, stronger sources (100 - 1000 counts) usually require 2T plasmas, and the strongest sources (1000 - 3000 counts) often require 2T or 3T plasmas with nonsolar elemental abundances.

Te_Plasma_1_Flag
This flag is set to ':' to indicates that there is an uncertainty in the corresponding plasma temperature.

Te_Plasma_1_Error
The uncertainty in the temperature of the single plasma temperature, in keV. This parameter is provided only for the Chandra X-ray sources with stellar counterparts.

Te_Plasma_2
The plasma temperature of the best-fit Mewe and Kaastra (higher-temperature) plasma component, in keV. This parameter is provided only for the Chandra X-ray sources with stellar counterparts.

Log_Lx_SB
The logarithm of the X-Ray luminosity of the stellar X-ray source, in the soft 0.5 - 2 keV band, in erg/s. The X-ray luminosities assume the star lies at a distance of 160 pc and include a correction for the 5% of the counts outside the extraction box. The field stars discussed in Section 5 of the published paper lie on the far side of the cloud at unknown distances, so their X-ray luminosities are greater than their tabulated values.

Log_Lx_Obs
The logarithm of the observed X-Ray luminosity of the stellar X-ray source, in the total 0.5 - 8 keV band, in erg/s. The X-ray luminosities assume the star lies at a distance of 160 pc and include a correction for the 5% of the counts outside the extraction box. The field stars discussed in Section 5 of the published paper lie on the far side of the cloud at unknown distances, so their X-ray luminosities are greater than their tabulated values.

Log_Lx
The logarithm of the absorption-corrected X-ray luminosity of the stellar X-ray source, in the total 0.5 - 8 keV band, in erg/s. The X-ray luminosities assume the star lies at a distance of 160 pc and include a correction for the 5% of the counts outside the extraction box. The field stars discussed in Section 5 of the published paper lie on the far side of the cloud at unknown distances, so their X-ray luminosities are greater than their tabulated values.

Property_Flags
This six-character parameter contains flags indicating the properties of the stellar counterpart to the X-ray source as taken from Carpenter et al. (2002, CDS Cat. <J/AJ/124/1001) in the following order (Y indicates the presence of the property, else the value is 0):

      Character   Property
      Position

      1           variable in the optical or K band
      2           H-alpha emission
      3           Li absorption
      4           previously known X-ray source (prior to the present study)
      5           infrared excess
      6           far-infrared source
  

Broad_Class
The classification type of the stellar counterpart to the X-ray source, defined as follows:

      WTT = weak-lined T Tauri star
      CTT = classical T Tauri star
      I   = embedded
      BD  = brown dwarf
      AB  = Herbig AeBe star
  

Rmag
The R magnitude of the stellar counterpart to the X-ray source, taken from the USNO-B1.0 Catalog (CDS Cat. <I/284>).

Imag
The i or I magnitude of the stellar counterpart to the X-ray source, taken from either the second DENIS data release (CDS Cat. <B/denis>) or from the aithors' own SAAO I survey (the referenced paper).

Jmag
The J magnitude of the stellar counterpart to the X-ray source, taken from the 2MASS survey.

Jmag_Flag
This flag is set to ':' to indicates that there is an uncertainty in the corresponding J magnitude.

Hmag
The H magnitude of the stellar counterpart to the X-ray source, taken from the 2MASS survey.

Hmag_Flag
This flag is set to ':' to indicates that there is an uncertainty in the corresponding H magnitude.

Kmag_Limit
This flag is set to '>' to indicates that the quoted K magnitude is a lower limit, i.e., the object was not detected in this band.

Kmag
The K magnitude of the stellar counterpart to the X-ray source, taken from the 2MASS survey.

Kmag_Flag
This flag is set to ':' to indicates that there is an uncertainty in the corresponding K magnitude.

Iso_6p7um_Mag
The 6.7-micron band magnitude of the stellar counterpart to the X-ray source, taken from the Infrared Space Observatory (ISO) survey.

Iso_14p3um_Mag
The 14.3-micron band magnitude of the stellar counterpart to the X-ray source, taken from the Infrared Space Observatory (ISO) survey.

Spect_Type
The spectral type of the stellar counterpart to the X-ray source, taken from Luhman (2004ApJ...602..816L).

Log_L_Bol
The logarithm of the bolometric luminosity of the stellar counterpart to the X-ray source, in solar luminosities, taken from Luhman (2004ApJ...602..816L).

Log_L_Bol_Flag
This flag is set to '?' to indicates that there is an uncertainty in the corresponding bolometric luminosity.

Stellar_Mass
The mass of the stellar counterpart to the X-ray source, in solar masses, taken from Luhman (2004ApJ...602..816L).

Stellar_Mass_Flag
This flag is set to ':' to indicates that there is an uncertainty in the corresponding stellar mass.

Stellar_Age_Limit
This flag is set to '<' to indicates that the quoted stellar age is an upper limit.

Stellar_Age
The age of of the stellar counterpart to the X-ray source, in millions of years (Myr), taken from Luhman (2004ApJ...602..816L).

Class
The HEASARC Browse classification of the stellar counterpart to the X-ray source, based on the value of the spect_type parameter.


Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 17-Feb-2007