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MONR2CXO - Monoceros R2 Cloud Chandra X-Ray Point Source Catalog



The Monoceros R2 (Mon R2) Cloud X-Ray Point Source Catalog contains the results of the Chandra ACIS-I observation of the central region of this high-mass star-forming region (SFR), which lies at a distance of 830pc. With a deep exposure of ~ 100 ks, the authors detected 368 X-ray sources, ~80% of which were identified with near-infrared (NIR) counterparts. They systematically analyzed the spectra and time variability of most of the X-ray emitting sources and provide a comprehensive X-ray source catalog for the first time. Using the J-, H- and K-bands magnitudes of the NIR counterparts, they have estimated the evolutionary phase, classical T Tauri (CTT) stars and weak-lined T Tauri (WTT) stars, and the masses of the X-ray emitting sources, and have analyzed their X-ray properties as a function of age and mass. They found a marginal hint that CTT stars have a slightly higher temperature (2.4 keV) that of WTT stars (2.0 keV). A significant fraction of the high- and intermediate-mass sources have time variability and high plasma temperatures (2.7 keV) simailar to those of the low-mass stars (2.0 keV). This supports earlier proposals that high- and intermediate-mass young stellar objects emit X-rays via magnetic activity. The authors also found a significant difference in the spatial distribution between X-ray and NIR sources.

Catalog Bibcode



X-ray observation on the Monoceros R2 star-forming region with the
Chandra ACIS-I array.
    Nakajima H., Imanishi K., Takagi S., Koyama K., Tsujimoto M.
   <Publ. Astron. Soc. Jap., 55, 635 (2003)>


This table was created by the HEASARC in January 2007 based on CDS table J/PASJ/55/635/table1.dat


A running source number in order of increasing J2000.0 Right Ascension.

The X-ray source name based on the '[NIT2003]' prefix (for Nakajima, Imanishi, Takagi... 2003) and the source number, as recommended by the CDS Dictionary of Astronomical Nomenclature.

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. An astrometric correction of -0.87" was applied to the original ACIS-I RAs in order to register them to the 2MASS frame.

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. An astrometric correction of -0.75" was applied to the original ACIS-I Declinations in order to register them to the 2MASS frame.

The Galactic Longitude of the X-ray source.

The Galactic Latitude of the X-ray source.

The background-subtracted photon counts for the X-ray source in the 0.5 - 10.0 keV band. Sources were detected using the wavdetect algorithm in the CIAO package, version 2.2, in this energy band with a threshold significance of 10^-6 and wavelet scales from 1 to 16 pixels in multiple of sqrt(2). Sources with X-ray counts of less than 3 times the background were discarded. The X-ray photons of each source were accumulated in a circular region with a radius of 0.7" - 15.4, depending on the point-sprread function (PSF), which is a function of the angular distance from the telescope optical axis direction of 6 07 50.86, -06 22 50.0 (J2000). The background photons were extracted from a source-free circle of ~42" in radius.

Previous X-ray identifications for the X-ray source, where KKH stands for a source listed by Kohno et al. (2002, CDS Cat. <J/ApJ/567/423>), identified as [KKH2002] NNN in Simbad, and GMCF for a source from Gregorio-Hetem et al. (1998A&A...331..193G), identified as [GMC98] Mon X-NN in Simbad.

The identification of the NIR counterpart to the X-ray source, as follows:

  CMDSH: Carpenter et al. (1997, CDS Cat. <J/AJ/114/198>), [CMD97] NNNN in Simbad
  2MASSI: 2MASS Point Source Catalog in the Second Incremental Data Release,
          Cat. <II/241>
  NIR source names such as d_N and IRS4 are from Beckwith et al.
  (1976ApJ...208..390B, [BEB76] IRS N), Howard et al. (1994ApJ...425..707H,
  [AW90] aW, [BEB76] IRS NWW), and Carpenter et al. (1997, CDS Cat.
  <J/AJ/114/198>). (i.e. d_N = [AW90] dN, IRS 4 = [BEB76] IRS 4 in Simbad)
NIR counterparts to X-ray sources were selected using the criterion that the angular distance between the X-ray and NIR sources be smaller than the root mean square of the positional uncertainty derived from the wavdetect program and the PSF radius. In cases with multiple counterparts, the closest one was always chosen.

Contact Person

Questions regarding the MONR2CXO database table can be addressed to the HEASARC User Hotline.
Page Author: Browse Software Development Team
Last Modified: Wednesday, 24-Jan-2007 17:52:57 EST