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LMC30DRCXO - LMC 30 Doradus Complex Chandra X-Ray Point Source Catalog

HEASARC
Archive

Overview

This table contains the results of a study of the X-ray point-source population of the 30 Doradus (30 Dor) star-forming complex in the Large Magellanic Cloud (LMC) using high spatial-resolution X-ray images and spatially-resolved spectra obtained with the Advanced CCD Imaging Spectrometer (ACIS) on board the Chandra X-Ray Observatory. The observation of ~21 ks was made on 1999 September 21 and placed the cluster R136 at the aim point of the ACIS Imaging Array (ACIS-I). This table lists the the X-ray sources detected in the 17' x 17' field centered on R136, the massive star cluster which lies at the center of the main 30 Dor nebula. 20 of the 32 Wolf-Rayet stars in the ACIS field are detected. The cluster R136 is resolved at the subarcsecond level into almost 100 X-ray sources, including many typical O3-O5 stars, as well as a few bright X-ray sources which hade been previously reported. Over 2 orders of magnitude of scatter in the X-ray luminosity L_x (calculated assuming a distance of 50 kpc) is seen among R136 O stars, suggesting that X-ray emission in the most massive stars depends critically on the details of wind properties and the binarity of each system, rather than reflecting the widely reported characteristic value L_x/L_bol ~10^-7. Such a canonical ratio may exist for single massive stars in R136, but these data are too shallow to confirm this relationship. Through this and more recent X-ray studies of 30 Dor, the complete life cycle of a massive stellar cluster can be revealed.

This HEASARC table contains both the primary high-significance X-ray sources as well as some lower-significance tentative X-ray sources. The latter sources should not be considered definitive. A subsequent Chandra observation of this field, with several times the exposure of this observation, will result in a longer, more complete list of point sources than that given in this paper.


Catalog Bibcode

2006AJ....131.2164T

References

A Chandra/ACIS Study of 30 Doradus II. X-ray Point Sources in the Massive Star
Cluster R136 and Beyond
    Townsley L.K., Broos P.S., Feigelson E.D., Garmire G.P., Getman K.V.
   <Astron. J., 131, 2164-2184 (2006)>
   =2006AJ....131.2164T

Provenance

This table was created by the HEASARC in February 2007 based on the merger of electronic versions of Tables 1, 2 and 5 from the above reference which were obtained from the AJ website. It does not include the results from the spectral analysis of 49 of the X-ray sources having a photometric significance (signal-to-noise ratio) greater than 2 which are presented in Tables 3 and 4 of the reference paper.

HEASARC Implementation

The HEASARC has combined the main list of primary X-ray sources given in Table 1 of the above reference with the list of tentative sources given in Table 2 of the same. In order to clearly identify which table an entry was taken from, the HEASARC has created a parameter called source_sample which is set to 'primary' for entries from Table 1 and to 'tentative' for entries from Table 2.

Parameters

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

Alt_Name
An alternative name for the X-ray source using the '[TBF2006]' prefix (for Townsley, Broos and Feigelson 2006) and the source number, as recommended by the CDS Dictionary of Nomenclature of Celestial Objects.

Name
The standard Chandra X-ray source designation using the 'CXOU J' prefix and the truncated J2000.0 coordinates of the source (HHMMSS.ss-DDMMSS.s).

RA
The Right Ascension of the X-ray source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10^-6 degrees in the original tables.

Dec
The Declination of the X-ray source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10^-6 degrees in the original tables.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Error_Radius
The formal 1-sigma radial positional uncertainty (not inclusing any systematic uncertainty) based on source counts, as calculated by acis_extract, in arcseconds. See Section 3.1 of the reference paper for a more detailed discussion of the total positional uncertainty.

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

Counts
The net full-band (0.5 - 8 keV) extracted source counts.

Counts_Error
The 1-sigma error in the net full-band source counts, calculated using Gehrels' (1986, ApJ, 303, 336) equation 7.

Bck_Counts
The estimated number of background counts in the source extraction region.

HB_Counts
The net hard-band (2 - 8 keV) extracted source counts.

PSF_Fraction
The fraction of the PSF used to extract the source counts. Sources are extracted with a 90% PSF fraction unless they are in a crowded region. Thus, a value of less than 90% for the PSF fraction indicates that the source was crowded and that its properties may be influenced by nearby sources.

SNR
The photometric significance (signal-to-noise ratio) of the X-ray source, i.e., the ratio of the full-band counts to the error in the counts.

Prob_Fluct_Limit
This flag parameter is set to '<' if the probability that the source is a background fluctuation rather than a true point source is an upper limit rather than an actual value.

Prob_Fluct
The (logarithm of the) probability log(P_B) that the source is solely a background fluctuation in the full-band counts rather than a true point source. This represents the authors' primary test of source validity. As described in Section 2.1 of the reference paper, this quantity differentiates the 117 sources in the main source catalog (Table 1; those entries in this HEASARC table with source_sample = 'primary') which have values of P_B <= 0.003 from the 63 tentative source in Table 2 (those with source_sample = 'tentative') which have final values of P_B > 0.003.

Anomaly_Flags
This parameter contains a set of flags which can note the presence of various observational anomalies:

      g = fractional time that source was on a detector (FRACEXPO) is <0.9
      e = source on field edge
      p = source piled up
  

Variable_Flag
This parameter contains a flag which indicates the likelihood that the X-ray source is displaying variability, based on a calculation of the Kolmogorov-Smirnov statistic as first defined in Feigelson & Lawson (2004, ApJ, 614, 267). Notice that no variability test was performed for sources with fewer than 4 total full-band counts, and that no value is reported for sources in chip gaps or on field edges. The flag values are as follows:

      a = no evidence for variability
      b = possibly variable
  

Exposure
The effective exposure time of the X-ray source, in seconds, namely the length of time that the source would have to be observed at the Chandra aimpoint in order to collect the same number of counts as were actually obtained in the observation as performed.

Median_Energy
The estimated background-corrected median energy of the X-ray source in the full spectral band, in keV (see Section 3.1 of the reference paper for more details).

Offset
The angular separation between the Chandra source and its counterpart, using a hierarchy of matching catalogs, in arcseconds, as follows: if a match from Malumuth and Heap (1994, AJ, 107, 1054 = MH94) was available, then that separation is noted; if there was no MH94 match, then the separation from the 2MASS counterpart is noted; if neither of these matches exists, the separation between the ACIS source and its match from SIMBAD or Vizier is given.

Spect_Type
The spectral type of the counterpart star or multiple stellar system, if known, taken from Breysacher et al. (1999, A&AS, 137, 117 = BAT99), Crowther & Dessart (1998, MNRAS, 296, 622), or SIMBAD.

Bat99_Number
The Breysacher et al. (1999) catalog number of the counterpart star. BAT99 is a catalog of Wolf-Rayet stars in the LMC.

P93_Number
The Parker (1993, AJ, 106, 560 = P93) catalog number of the counterpart star. P93 is a ground-based UBV photometric study of 30 Dor.

Mh94_Number
The MH94 catalog number of the counterpart star. MH94 is a UBV photometric study of 30 Dor performed with the Hubble Space Telescope.

Ppl02_Name
The X-ray source identification from Portegies Zwart et al. (2002, ApJ, 574, 762 = PPL02)

RA_2MASS_J2000
The Right Ascension (J2000) of the 2MASS counterpart, in decimal degrees.

Dec_2MASS_J2000
The Declination (J2000) of the 2MASS counterpart, in decimal degrees.

Comments
This field contains matches to the Chandra X-ray source from other catalogs, common names for well-known sources, and other notes.

Source_Sample
The HEASARC has combined the main list of primary X-ray sources given in Table 1 of the reference paper with the list of tentative sources given in Table 2 of the same. In order to clearly identify which table an entry was taken from, the HEASARC has created this parameter which is set to 'primary' for entries from Table 1 and to 'tentative' for entries from Table 2.

Class
The HEASARC Browse object classification based on the value of the spect_type parameter, when the latter is populated.


Contact Person

Questions regarding the LMC30DRCXO database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 21-Feb-2007