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CMAR1XRAY - ROSAT PSPC Catalog of Canis Major R1 X-Ray Sources

HEASARC
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Overview

The CMa R1 star-forming region contains several compact clusters as well as many young early-B stars. It is associated with a well-known bright rimmed nebula, the nature of which is unclear (fossil HII region or supernova remnant). To help elucidate the nature of the nebula, the authors' goal was to reconstruct the star-formation history of the CMa R1 region, including the previously unknown older, fainter low-mass stellar population, using X-rays.

The authors analyzed images obtained with the ROSAT satellite, covering ~5 square degrees. Complementary VRI photometry was performed with the Gemini South telescope. Color-magnitude and color-color diagrams were used in conjunction with pre-main sequence evolutionary tracks to derive the masses and ages of the X-ray sources.

The ROSAT images show two distinct clusters. One is associated with the known optical clusters near Z CMa, to which ~ 40 members are added. The other, which the authors name the "GU CMa" cluster, is new, and contains ~ 60 members. The ROSAT sources are young stars with masses down to M_star ~ 0.5 M_sun, and ages up to 10 Myr. The mass functions of the two clusters are similar, but the GU CMa cluster is older than the cluster around Z CMa by at least a few Myr. Also, the GU CMa cluster is away from any molecular cloud, implying that star formation must have ceased; on the contrary (as already known), star formation is very active in the Z CMa region.

The two ROSAT observations that the authors analyzed are the following. By order of increasing RA, the first Field ('Field 1' hereafter), HEASARC ID RP201011 pointing axis RA(J2000} = 7h 00m, Dec(J2000) = -11o 30', has an exposure of 19.7 ks. 'Field 2', HEASARC ID RP201277, pointing axis RA(J2000) = 7h 04m, Dec(J2000) = -11o 33', has a much shorter exposure of 4.6 ks.

This table contains the complete list of sources detected in CMa R1 by ROSAT.


Catalog Bibcode

2009A&A...506..711G

References

Star formation history of Canis Major R1.
I. Wide-field X-ray study of the young stellar population.
    Gregorio-Hetem J., Montmerle T., Rodrigues C.V., Marciotto E.,
    Preibisch T., Zinnecker H.
   <Astron. Astrophys., 506, 711-727 (2009)>
   =2009A&A...506..711G

Provenance

This online catalog was created by the HEASARC in April 2010 based on machine-readable tables obtained from the CDS (their catalog J/A+A/506/711, file tablea1.dat).

Parameters

Source_Number
A sequential identification number in order of increasing J2000.0 Right Ascension for each ROSAT source in the catalog. Sources with source numbers from 1 to 56 were detected in Field 1, 57 to 61 in both fields, ands 62 to 98 in Field 2.

Name
The catalog source name as recommended by the authors, using the prefix 'CMaX' for Canis Majoris R1 X-ray source, and the source number.

HK_Excess_Flag
This flag parameter is set to 'e' to indicate the presence of an (H-K) excess in the relevant source.

Other_Xray_Flag
This flag parameter is set to 'x' to indicate the objects which were also detected by XMM-Newton and/or Chandra.

Source_Flags
This flag parameter is set to 'a', 'b', etc. to indicate that there are individual notes regarding the ROSAT source, as follows (here [C74] indicates Claria 1974AJ.....79.1022C, and [SEI99] to Shevchenko et al., 1999, CDS Cat. J/MNRAS/310/210):

         a = HD 51896 (F5)
         b = SS 75
         c = HD 52014 (F5)
         d = HD 52385 (K0)
         e = GU CMa, HD 52721 (B2V), [C74] 63 , [SEI99] 158
         f = FZ  CMa (B2.5), [C74] 67, [SEI99] 159
         g = Z CMa (Bpe), [C74] 76, [SEI99] 161
         h = BD -111762 (B2), [C74] 77, [SEI99] 92
         i = [C74] 14, [SEI99] 94
         j = Member of cluster vdB-RN92  (VDB 92 in Simbad)
         k = Member of cluster BRC 27 (NAME BRC 27 STAR CLUSTER in Simbad)
         l = [SEI99] 99
         m = Member of cluster NGC 2327
         n = [SEI99] 111
         o = HD 53339 (B3), C84, [SEI99]
         p = HD 53396 (B9), [SEI99] 112
  

Error_Radius
This positional uncertainty is descibed in the reference paper as the diameter of the positional error circle, in arcseconds. The HEASARC believes that is is actually the radius of the positional error circle, in arcseconds.

Count_Rate
The ROSAT X-ray source count rate, in counts per second (converted by the HEASARC from the original units of ct/ksec).

Count_Rate_Error
The RMS uncertainty in the ROSAT X-ray source count rate, in counts per second (converted by the HEASARC from the original units of ct/ksec).

SNR
The ROSAT X-ray source signal-to-noise ratio.

Log_Lx
The logarithm of the ROSAT X-ray source luminosity, in erg/s, in the 0.4-2.4 keV range. In these exposures, the number of X-ray counts per source was in general too small to allow deriving a spectrum, or even a good hardness ratio. Therefore, the intrinsic X-ray luminosity of the sources, known to be pre-main sequence (PMS) stars in this case, is based on the count rate, assuming an average plasma temperature (here kT_X ~ 1 keV), and is corrected for extinction using the column density given by N_H = 2.1 x 1021 A_V cm-2, the visual extinction A_V being determined by independent methods (see reference paper for more details). A typical value of the approximate X-ray luminosity L_X for A_V ~ 1 is based on the ROSAT count-to-flux ratio 1 ct/ks = 9 x 10-15 erg s-1 cm-2 (see details in Appendix A of the reference paper), where a distance of 1 kpc has been assumed. The corresponding lower limits to the stellar X-ray luminosities are 6 x 1029 erg s-1 for Field 1 and 1 x 1030 erg s-1 for Field 2.

RA
The Right Ascension of the optical counterpart when available, or of the ROSAT X-ray source centroid otherwise, in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.1 seconds of time in the original table.

Dec
The Declination of the optical counterpart when available, or of the ROSAT X-ray source centroid otherwise, in the selected equinox. This was given in J2000.0 coordinates to a precision of 1 arcsecond in the original table.

LII
The Galactic Longitude corresponding to the source position.

BII
The Galactic Latitude corresponding to the source position.

Position_Flag
This flag parameter is set to 'X;' to indicates that the position is of the X-ray source centroid, i.e., no optical counterpart was found.

Rmag
The R magnitude of the optical counterpart to the ROSAT X-ray source, obtained from the available catalogs.

A_Vmag
The extinction in the V band of the optical counterpart to the ROSAT X-ray source, obtained from the available catalogs.

Jmag
The 2MASS J magnitude of the counterpart to the ROSAT X-ray source.

Hmag
The 2MASS H magnitude of the counterpart to the ROSAT X-ray source.

Kmag
The 2MASS K magnitude of the counterpart to the ROSAT X-ray source.

Age_Limit
This flag parameter is set to '<' if the estimated age is an upper limit, or to '>' if if the estimated age is a lower limit.

Age
The lower bound to the estimated age of the pre-main sequence star, in megayears (Myr), based on its position in the near-IR color-magnitude diagrams, as discussed in the reference paper.

Upper_Age
The upper bound to the estimated age of the pre-main sequence star, in megayears (Myr), based on its position in the near-IR color-magnitude diagrams, as discussed in the reference paper.

Age_Flag
This flag parameter is set to '?' to indicate that the counterpart to the X-ray source was located outside of the isochrones in the J vs (J-H) color-magnitude diagram (Fig. 9 of the reference paper), either because of the probable presence of circumstellar material typical of PMS stars or (in 4 cases where the objects are located to the left side of the isochrones) because the objects are not the correct counterparts.

Mass_Limit
This flag parameter is set to '>' if the estimated mass is a lower limit.

Mass
The lower bound to the estimated mass of the pre-main sequence star, in solar masses, based on its position in the near-IR color-magnitude diagram, as discussed in the reference paper.

Upper_Mass
The upper bound to the estimated mass of the pre-main sequence star, in solar masses, based on its position in the near-IR color-magnitude diagram, as discussed in the reference paper.

Mass_Flag
This flag parameter is set to '?' to indicate that the counterpart to the X-ray source was located outside of the isochrones in the J vs (J-H) color-magnitude diagram (Fig. 9 of the reference paper), either because of the probable presence of circumstellar material typical of PMS stars or (in 4 cases where the objects are located to the left side of the isochrones) because the objects are not the correct counterparts.


Contact Person

Questions regarding the CMAR1XRAY database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 24-May-2012