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NGC2264XMM - NGC 2264 XMM-Newton X-Ray Point Source Catalog

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Overview

This table contains (some of) the results from an X-ray imaging survey of the young cluster NGC 2264, carried out with the European Photon Imaging Cameras (EPIC) on board the XMM-Newton spacecraft. XMM-Newton EPIC observations were made separately of the northern and southern portions of NGC 2264 on 2001 March 20 and 2002 March 17 - 18, respectively. Details concerning the two pointings are summarized in Table 1 of the reference paper. The nominal integration time was 42 ks for both observations. The three EPIC cameras were operated in full window mode. To prevent contamination of the X-ray images by the XUV and EUV emission of the optically and UV-bright sources in the field of view, the thick filter was used, which imposes a strong cut-off in the response at the lower energies. The X-ray data are merged with extant optical and near-infrared photometry, spectral classifications, H-alpha emission strengths, and rotation periods to examine the interrelationships between coronal and chromospheric activity, rotation, stellar mass, and internal structure for a statistically significant sample of pre-main-sequence stars. Out of the 316 distinct point-like sources that were detected at >= 3-sigma levels in one or more of six EPIC images, a total of 300 distinct X-ray sources can be identified with optical or near-infrared counterparts.

The sources are concentrated within three regions of the cluster: in the vicinity of S Mon, within the large emission/reflection nebulosity southwest of S Mon, and along the broad ridge of molecular gas that extends from the Cone Nebula to the NGC 2264 IRS 2 field. From the extinction-corrected color-magnitude diagram of the cluster, ages and masses for the optically identified X-ray sources are derived. A median age of ~ 2.5 Myr and an apparent age dispersion of ~ 5 Myr are suggested by pre-main-sequence evolutionary models. The X-ray luminosity of the detected sources appears well-correlated with bolometric luminosity, although there is considerable scatter in the relationship. Stellar mass contributes significantly to this dispersion, while isochronal age and rotation do not. X-ray luminosity and mass are well correlated such that L_X ~ (M/Msolar)1.5, which is similar to the relationship found within the younger Orion Nebula Cluster. No strong evidence is found for a correlation between E(H-K), the near-infrared color excess, and the fractional X-ray luminosity, which suggests that optically thick dust disks have little direct influence on the observed X-ray activity levels.

Among the X-ray-detected weak-line T Tauri stars, the fractional X-ray luminosity, L_X/L_bol, is moderately well correlated with the fractional H-alpha luminosity, L_H(alpha)/L_bol, but only at the 2-sigma level of significance. The cumulative distribution functions for the X-ray luminosities of the X-ray-detected classical and weak-line T Tauri stars within the cluster are comparable, assuming the demarcation between the two classes is at an H-alpha equivalent width of 10 Angstroms. However, if the non-detections in X-rays for the entire sample of H-alpha emitters known within the cluster are taken into account, then the cumulative distribution functions of these two groups are clearly different, such that classical T Tauri stars are underdetected by at least a factor of 2 relative to the weak-line T Tauri stars. Examining a small subsample of X-ray-detected stars that are probable accretors based on the presence of strong H-alpha emission and near-infrared excess, the authors conclude that definitive nonaccretors are ~ 1.6 times more X-ray luminous than their accreting counterparts. In agreement with earlier published findings for the Orion Nebula Cluster, the authors find a slight positive correlation (valid at the 2-sigma confidence level) between L_X/L_bol and the rotation period in NGC 2264 stars. The lack of a strong anticorrelation between X-ray activity and rotation period in the stellar population of NGC 2264 suggests that either the deeply convective T Tauri stars are rotationally saturated or that the physical mechanism responsible for generating magnetic fields in pre-main-sequence stars is distinct from the one that operates in evolved main-sequence stars.


Catalog Bibcode

2007AJ....134..999D

References

X-Ray Observations of the Young Cluster NGC 2264
    Dahm S.E., Simon T., Proszkow E.M., Patten B.M.
   <Astron. J. 134, 999 (2007)>
   =2007AJ....134..999D

Provenance

This table was created by the HEASARC in September 2007 based on the electronic version of Table 2 from the reference paper which was obtained from the electronic AJ site.

Parameters

Source_Number
A running X-ray source number in order of decreasing J2000.0 Declination which uniquely identifies each X-ray source. Note that results for sources in the small overlap region of the two fields are averaged.

Name
The name for the X-ray source using the '[DSP2007]' prefix (for Dahm, Simon, Proszkow, 2007) and the X-ray source number, as recommended by the CDS Dictionary of Nomenclature of Celestial Objects. In the reference paper, the authors use the prefix 'UHX' for these sources, notice, but this usage is deprecated by the CDS.

Source_Flag
This flag parameter is set to l to indicate that the X-ray source counterpart is an adaptive optics binary. The following sources fall into this category:

   UHX = [DSP2007] number (separation [arcsec], position angle [degrees]):

          UHX 10 (0.32, 41.3);
          UHX 68 (1.21, 325.2);
          UHX 92 (1.33, 148.0);
          UHX 102 (0.27, 184.6);
          UHX 135 (1.74, 91.3);
          UHX 148 (0.20, 211.1);
          UHX 169 (1.98, 163.7);
          UHX 170 (1.11, 180.6);
          UHX 201 (2.13, 133.4);
          UHX 228 (2.34, 301.3);
          UHX 231 (0.89, 63.6);
          UHX 261 (0.17, 32.1)
  

RA
The Right Ascension of the X-ray source in the selected equinox. This was given implicitly in the alt_name parameter (see below) in J2000.0 coordinates to a precision of 0.1 seconds of time in the table in the reference paper. The agreement between the ground-based astrometry and the XMM-Newton source positions was typically 2" or better.

Dec
The Declination of the X-ray source in the selected equinox. This was given implicitly in the alt_name parameter (see below) in J2000.0 coordinates to a precision of 1 arcsecond in the table in the reference paper. The agreement between the ground-based astrometry and the XMM-Newton source positions was typically 2" or better.

LII
The Galactic Longitude of the X-ray source

BII
The Galactic Latitude of the X-ray source.

Alt_Name
The alternative X-ray source designation using the 'XMMU' prefix recommended by the CDS Dictionary of Nomenclature of Celestial Objects. and the J2000 coordinates of the X-ray source, e.g., 'XMMU J063955.5+094734'.

Optical_Name
The name(s) of the optical or near-infrared (NIR) counterparts to the X-ray source. The following abbreviations were used:

            W = Walker (1956, ApJS, 2, 365)
  LkHa or LHa = Herbig (1954, ApJ, 119, 483)
          VSB = Vasilevskis et al. (1965, AJ, 70, 797)
          FMS = Flaccomio et al. (1999, A&A, 345, 521)
          SBL = Sung et al. (1997, AJ, 114, 2644)
          PSB = Park et al. (2000, AJ, 120, 894)
          LBM = Lamm et al. (2004, A&A, 417, 557)
          UPa = Koch & Perry (1974, AJ, 79, 379)
        ESOHa = Reipurth et al. (2004, AJ, 127, 1117)
          KHa = Ogura (1984, PASJ, 36, 139)
          RMS = Rebull et al. (2002, AJ, 123, 1528)
          UHa = Dahm & Simon (2005, AJ, 129, 829; Paper I)
  
where we have replaced 'H-alpha' in the names by 'Ha', as recommended by the CDS Dictionary of Nomenclature of Celestial Objects.

Count_Rate
The count rate in counts per second of the X-ray source from the pn camera or from one of the two MOS cameras if counts were not available from the pn camera. In the latter case, the value of the count_rate_flag parameter has been set to 'm'. The measured values have been corrected to 100% encircled energy fraction using the analytical expression derived by Simon & Dahm (2005, ApJ, 618, 795).

Count_Rate_Error
The associated measurement error in the X-ray source count rate, in counts per second.

Count_Rate_Flag
This flag parameter is set to 'm' to indicate that the quoted count_rate value is the MOS count rate, not the EPIC PN count rate.

Extraction_Fraction
The fractional throughput, in percent, of the extraction aperture used for the specified X-ray source, i.e., the encircled energy fraction of the measurement cell.

Exposure
The effective exposure time, in seconds (s), at the position of the X-ray source as determined from the EPIC exposure maps.

Vmag_Extinction
The authors' estimate of the optical (V-band) extinction towards the source, derived from the color excess assuming the normal ratio of the total-to-selective absorption.

Log_Lx
The logarithm of the foreground extinction-corrected X-ray luminosity log L_x of the source in the 0.3 - 15 keV energy range. This was scaled from the observed count rate using the appropriate counts-to-energy conversion factor (ECF), in units of erg/s, assuming a distance to NGC 2264 of 800 pc. (See Section 2 of the reference paper for more details on the ECFs). The L_x values are variance-weighted averages of the results obtained for each source from the three independent EPIC cameras.

Log_Lx_Error
The uncertainty in log L_x of the source, based on the scatter in the results from the separate cameras and thus indicating the internal consistency of the independently measured count rates and the resulting scaled luminosities.

Vmag
The V-band magnitude of the optical counterpart to the X-ray source, taken from Simon & Dahm (2005, ApJ, 618, 795; Paper I) or the literature as referenced in the text of the paper.

VR_Color
The V-band to R_c (Cousins R) (V - R_C) color index of the optical counterpart to the X-ray source, taken from Simon & Dahm (2005, ApJ, 618, 795; Paper I) or the literature as referenced in the text of the paper.

VI_Color
The V-band to I_c (Cousins I) (V - I_C) color index of the optical counterpart to the X-ray source, taken from Simon & Dahm (2005, ApJ, 618, 795; Paper I) or the literature as referenced in the text of the paper.

Jmag
The 2MASS J band magnitude of the NIR counterpart to the X-ray source,

JH_Color
The 2MASS (J-H) color of the NIR counterpart to the X-ray source,

HK_Color
The 2MASS (H - K_S) color of the NIR counterpart to the X-ray source,

Halpha_EW
The H(alpha) equivalent width in the spectrum of the optical counterpart to the X-ray source, if emission is present, in Angstroms, from Simon & Dahm (2005, ApJ, 618, 795; Paper I).

Log_Age
The logarithm of the theoretical stellar age, in years, derived from the evolutionary models of Siess et al. (2000, A&A, 358, 593).

Mass
The theoretical stellar mass, in solar masses, derived from the evolutionary models of Siess et al. (2000, A&A, 358, 593).


Contact Person

Questions regarding the NGC2264XMM database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 28-Aug-2012