NGC2264XMM - NGC 2264 XMM-Newton X-Ray Point Source Catalog
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.
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
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.
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.
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)
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.
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.
The Galactic Longitude of the X-ray source
The Galactic Latitude of the X-ray source.
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'.
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.
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).
The associated measurement error in the X-ray source count rate, in counts per second.
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.
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.
The effective exposure time, in seconds (s), at the position of the X-ray source as determined from the EPIC exposure maps.
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.
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.
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.
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.
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.
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.
The 2MASS J band magnitude of the NIR counterpart to the X-ray source,
The 2MASS (J-H) color of the NIR counterpart to the X-ray source,
The 2MASS (H - K_S) color of the NIR counterpart to the X-ray source,
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).
The logarithm of the theoretical stellar age, in years, derived from the evolutionary models of Siess et al. (2000, A&A, 358, 593).
The theoretical stellar mass, in solar masses, derived from the evolutionary models of Siess et al. (2000, A&A, 358, 593).