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NGC2362CXO - NGC 2362 Chandra X-Ray Point Source Catalog

HEASARC
Archive

Overview

This table contains the results of an obervation of the young cluster NGC 2362 in X-rays with Chandra ACIS-I in which 387 point X-ray sources, most of which are shown to be cluster members, were detected using PWDetect, a wavelet-based source detection algorithm, with a detection threshold chosen to ensure no more than one spurious detection in the entire ACIS FOV. The table lists all of the detected X-ray sources and their basic X-ray properties, as well as their proposed identifications with optical stars, using data from Moitinho et al. (2001ApJ...563L..73M; UBVRI photometry) and Dahm (2005, CDS Cat. <J/AJ/130/1805>; H-alpha data), as well as newer photometric data from Moitinho et al. (2005, in 'Cores to Clusters' [A&SSL, 324], 167). A matching position of less than 4 times the X-ray positional uncertainty of the X-ray source from PWDetect was used. Also included in the table is a classification of the optically-identified X-ray sources, based on their positions in the HR Diagram, which helps to separate rather clearly the cluster members from interloping field objects.

Catalog Bibcode

2006A&A...460..133D

References

The young star cluster NGC 2362: low-mass population and initial mass
function from a Chandra X-ray observation.
    Damiani F., Micela G., Sciortino S., Huelamo N., Moitinho A.,
    Harnden F.R.Jr., Murray S.S.
    <Astron. Astrophys. 460, 133 (2006)>
    =2006A&A...460..133D        (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in March 2007 based on CDS table J/A+A/460/133 files table2.dat and table3.dat.

HEASARC Implementation

This table merges the list of 387 X-ray sources (Table 2 from the reference paper) with the list of 320 optical counterparts (Table 3 from the reference paper). 306 of the X-ray sources have a single proposed optical counterpart each, 74 have no counterparts, and 7 have two counterparts. For the latter sources, there are 2 entries each in this table, one for each counterpart, with the X-ray data duplicated for each entry. There are thus 387 + 7 = 394 entries in this table. To make this structure more explicit, the HEASARC has created a parameter called ctrprt_number which is set to 0 for X-ray sources with no counterparts, 1 for the first or only counterparts to X-ray sources, and 2 for the second listed counterparts to those 7 X-ray sources which have 2 counterparts.

Parameters

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

Ctrprt_Number
This HEASARC-created parameter is set to 0 for those 74 X-ray sources which have no optical counterparts, to 1 for the first (7 sources) or only (306 sources) optical counterparts to X-ray sources, and to 2 for the second listed counterparts to those 7 X-ray sources which have 2 counterparts.

Name
The name for the X-ray source using the '[DMS2006b]' prefix (for Damiani, Micela and Sciortino, 2nd 2006 paper) and the source number, as recommended by the CDS Dictionary of Nomenclature of Celestial Objects.

RA
The Right Ascension of the X-ray source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.01 seconds of time in the original table. The X-ray positions were corrected for a systematic offset between their original values and those of the optical counterparts found in Moitinho et al.'s (2001, ApJ, 563, L73) catalog or in newer VLT/FORS1 photometric observations (Moitinho et al. 2005, in 'Cores to Clusters' [A&SSL, 324], 167) by shifting them by 0.43" in RA.

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 corrected for a systematic offset between their original values and those of the optical counterparts found in Moitinho et al.'s (2001, ApJ, 563, L73) catalog or in newer VLT/FORS1 photometric observations (Moitinho et al. 2005, in 'Cores to Clusters' [A&SSL, 324], 167) by shifting them by -0.07" in Declination.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Error_Radius
The positional uncertainty of the X-ray source location, in arcseconds, from PWDetect.

Count_Rate
The count rate of the X-ray source, in ct/s, assumed by the HEASARC to be in the 0.3 - 8.0 keV energy range, although this needs to be confirmed.

Count_Rate_Error
The uncertainty in the X-ray count rate, in ct/s.

Prob_Constant
The probability that the X-ray source exhibits no variability, i.e., is constant, in percent, from the Kolmogorov-Smirnov statitical test. $8 of the 387 sources were found to variable with more than 99% confidence.

Hardness_Ratio_1
The 'soft' hardness ratio HR_1, defined as (M-S)/(M+S), based on the X-ray counts collected in two of three energy bands S, M, H (respectively soft: [0.3 - 1.2 keV], medium: [1.2 - 2.2 keV] and hard: [2.2 - 8.0 keV]).

Hardness_Ratio_2
The 'hard' hardness ratio HR_2, defined as (H-M)/(H+M), based on the X-ray counts collected in two of three energy bands S, M, H (respectively soft: [0.3 - 1.2 keV], medium: [1.2 - 2.2 keV] and hard: [2.2 - 8.0 keV]).

Log_Lx
The logarithm of the X-ray source luminosity in the 0.2 - 4.0 keV band, in erg/s. To convert X-ray count rates to fluxes and luminosities for the cluster sources, conversion factors were derived by adopting absorbed (with the column density fixed at a value of 6.88 x 10^20 cm^-2 corresponding to the cluster optical extinction) APEC thermal models with 3 temperatures for strong sources (>100 ACIS counts), or 2 temperatures for weak sources. The resulting conversion factors from count rates to fluxes are 6.564 x 10^-12 erg cm^-2 ct^-1 and 10.16 x 10^-12 erg cm^-2 ct^-1 for the weak and strong sources, respectively. To calculate the X-ray luminosities, a distance of 1500 pc was adopted for NGC 2362. The weakest detected sources have values of log L_X ~ 29.0.

Log_Lx_Quiescent
The logarithm of the quiescent X-ray source luminosity in the 0.2 - 4.0 keV band, in erg/s, using the same conversion factors as for log L_X. A quiescent X-ray luminosity was defined for sources showing X-ray flares, for which cases the authors tried to model and subtract off the flare contribution, leaving only the non-variable component of the emission.

Moitinho_Number
The optical star number from the Moitinho et al. (2001ApJ...563L..73M) Catalog.

Offset
The angular offset between the X-ray and optical counterpart positions, in arcseconds.

Vmag
The V-band magnitude of the optical counterpart to the X-ray source, from the Moitinho et al. (2001ApJ...563L..73M) Catalog.

VI_Color
The V-I color of the optical counterpart to the X-ray source, from the Moitinho et al. (2001ApJ...563L..73M) Catalog.

Dahm_Number
The optical star number NNN from the Dahm (2005, <J/AJ/130/1805>) Catalog: such stars are identified as 'Cl* NGC 2362 D NNN' in SIMBAD.

Ew_Halpha
The H-alpha equivalent width of the optical counterpart, in Angstroms, if in the Dahm (2005, Cat. <J/AJ/130/1805>) Catalog.

Cm_Group
A grouping/classification of the optical counterpart, based on its position in the (V-I) vs V Color-Magnitude Diagram as indicated in Fig. 5 of the reference paper, essentially as follows:

  group 1 stars are (candidate) high-mass main-sequence cluster members;
  group 2 stars are (candidate) intermediate-mass main-sequence cluster members;
  group 3 stars fall in a narrow pre-main-sequence locus and are the best
        candidates to be low-mass PMS members;
  group 4 stars fall slightly above the Group 3 locus and are possible
        binary cluster members;
  group 5 stars fall below the Group 3 locus;
  group 6 stars fall elsewhere in the diagram and are considered not to be
        cluster members.
  

Contact Person

Questions regarding the NGC2362CXO database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 2-Mar-2007