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CHESSCAT - ChaMP Extended Stellar Survey (ChESS) X-Ray Catalog

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Overview

The ChaMP Extended Stellar Survey (ChESS) X-ray catalog contains 348 X-ray-emitting stars identified from correlating the Extended Chandra Multiwavelength Project (ChaMP), a wide-area serendipitous survey based on archival X-ray images, with the Sloan Digital Sky Survey (SDSS). The authors used morphological star/galaxy separation, matching to an SDSS quasar catalog, an optical color-magnitude cut, and X-ray data-quality tests to create this catalog, from a sample of 2121 matched ChaMP/SDSS sources. Their cuts retain 92% of the spectroscopically confirmed stars in the original sample while excluding 99.6% of the 684 spectroscopically confirmed extragalactic sources. Fewer than 3% of the sources in their final catalog are previously identified stellar X-ray emitters. For 42 catalog members, spectroscopic classifications are available in the literature. New spectral classifications and H-alpha measurements are presented for an additional 79 stars. The catalog is dominated by main-sequence stars; the authors estimate the fraction of giants in ChESS to be ~10%. They identify seven giant stars (including a possible Cepheid and an RR Lyrae star) as ChaMP sources, as well as three cataclysmic variables. They derive distances from ~10 to 2000 pc for the stars in the catalog using photometric parallax relations appropriate for dwarfs on the main sequence and calculate their X-ray and bolometric luminosities. These stars lie in a unique space in the L_X-distance plane, filling the gap between the nearby stars identified as counterparts to sources in the ROSAT All Sky Survey and the more distant stars detected in deep Chandra and XMM-Newton surveys. For 36 newly identified X-ray-emitting M stars, the authors calculated L_H-alpha/L_bol. The quantities L_H-alpha/L_bol and L_X/L_bol are linearly related below L_X/L_bol ~ 3 x 10-4, while L_H-alpha/L_bol appears to turn over at larger L_X/L_bol values. Stars with reliable SDSS photometry have an ~0.1 mag blue excess in u-g, likely due to increased chromospheric continuum emission. Photometric metallicity estimates suggest that the sample is evenly split between the young and old disk populations of the Galaxy; the lowest activity sources belong to the old disk population, a clear signature of the decay of magnetic activity with age.

Catalog Bibcode

2008ApJS..178..339C

References

The ChaMP Extended Stellar Survey (ChESS): Photometric and Spectroscopic
Properties of Serendipitously Detected Stellar X-Ray Sources.
    Covey K.R., Agueros M.A., Green P.J., Haggard D., Barkhouse W.A.,
    Drake J., Evans N., Kashyap V., Kim D.-W., Mossman A., Pease D.O.,
    Silverman J.D.
   <Astrophys. J. Suppl. 178, 339. (2008).
   =2008ApJS..178..339C

Provenance

This table was created by the HEASARC in January 2009 based on the electronic version of Tables 2 and 3 from the reference paper which were obtained from the ApJ web site.

Parameters

Name
The name of the source using the J2000.0 position-based designation for Chandra X-Ray Observatory Multi-wavelength Project (CXOMP) sources.

RA
The Right Ascension of the X-ray source in the selected equinox. This was created from the J2000.0 position-based name of the source, and thus has a precision of 0.1 seconds of time.

Dec
The Declination of the X-ray source in the selected equinox. This was created from the J2000.0 position-based name of the source, and thus has a precision of 1 arcsecond.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Source_Flags
This parameter contains flag(s) [bcde] indicating the following note(s) about the sources:

      b = Sources more than 12 arcmin from the Chandra ACIS-I optical axis
          direction. The authors have conservatively increased their X-ray
          flux error by 50% in such cases.
      c = Sources on ACIS S4, which suffers from increased noise and streaking
          relative to the other Chandra ACIS-I CCDs. The authors have
          conservatively increased their X-ray flux errors by ~20% to account
          for potential systematic effects in such cases.
      d = Sources which overlap other X-ray sources such that their positional
          separation is less than the radius of the PSF width encircling 95% of
          their flux. The authors have conservatively doubled the X-ray flux
          errors in such cases.
      e = A strong extended X-ray source ~30 arcsec distant may increase the
          flux errors quoted here by up to ~30%.
  

ObsID
The Chandra Observation Identification (obsid) number.

Flux
The broad-band (0.3-8.0 keV) X-ray flux of the source, in erg/s/cm2.

Flux_Error
The uncertainty in the broad-band (0.3-8.0 keV) X-ray flux of the source, erg/s/cm2.

Counts
The net broad-band (0.3-8.0 keV) X-ray source counts.

Counts_Error
The uncertainty in the net broad-band (0.3-8.0 keV) X-ray counts.

SB_Flux
The soft (0.5-2.0 keV) X-ray flux of the source, in erg/s/cm2.

SB_Flux_Error
The uncertainty in the soft (0.5-2.0 keV) X-ray flux of the source, in erg/s/cm2.

SB_Counts
The net soft (0.5-2.0 keV) X-ray source counts.

SB_Counts_Error
The uncertainty in the net soft (0.5-2.0 keV) X-ray source counts.

Hardness_Ratio
The hardness ratio HR, where HR = (H_c-S_c)/(H_c+S_c) and H_c and S_c are the number of hard and soft counts in the X-ray source. Since the authors do not include any scientific results based on HR in the reference paper, we simply characterize the typical errors here by noting that the mean error on HR is well-fit for sources with HR > -0.98 by HR_err = 0.36 +/- 0.027 *HR + 0.40 +/- 0.022, with RMS residuals (sigma) of 0.074. Sources with HR < -0.98 have median HR errors of 0.106, with RMS residuals (sigma) = 0.073.

Log_SB_Lx
The log of the soft (0.5-2.0 keV) X-ray luminosity of the X-ray source, in units of erg/s.

Log_SB_Lx_Error
The uncertainty in the log of the soft (0.5-2.0 keV) X-ray source luminosity, in units of erg/s.

Log_SB_Lx_Lbol
The log of the ratio of the soft X-ray (0.5-2.0 keV) to the bolometric luminosities of the source.

Log_SB_Lx_Lbol_Error
The uncertainty in the log of the ratio of the soft X-ray (0.5-2.0 keV) to the bolometric luminosities.

Log_Lx
The log of the broad-band (0.3-8.0 keV) X-ray source luminosity, in units of erg/s.

Log_Lx_Error
The uncertainty in the log of the broad-band X-ray source luminosity, in units of erg/s.

Log_Lx_Lbol
The log of the ratio of the broad-band (0.3-8.0 keV) to the bolometric luminosities of the source.

Log_Lx_Lbol_Error
The uncertainty in the log of the ratio of the broad-band (0.3-8.0 keV) to the bolometric luminosities of the source.

Offset
The angular separation between the SDSS and the Chandra positions, in arcseconds.

Imag
The SDSS i-band magnitude of the optical counterpart to the X-ray source.

Imag_Error
The uncertainty in the SDSS i-band magnitude of the optical counterpart to the X-ray source.

Ug_Color
The SDSS (u-g) color of the optical counterpart to the X-ray source.

Ug_Color_Error
The uncertainty in the SDSS (u-g) color of the optical counterpart to the X-ray source.

GR_Color
The SDSS (g-r) color of the optical counterpart to the X-ray source.

GR_Color_Error
The uncertainty in the SDSS (g-r) color of the optical counterpart to the X-ray source.

RI_Color
The SDSS (r-i) color of the optical counterpart to the X-ray source.

RI_Color_Error
The uncertainty in the SDSS (r-i) color of the optical counterpart to the X-ray source.

Iz_Color
The SDSS (i-z) color of the optical counterpart to the X-ray source.

Iz_Color_Error
The uncertainty in the SDSS (i-z) color of the optical counterpart to the X-ray source.

Synth_Gmag
The synthetic SDSS g-band magnitude of the optical counterpart to the X-ray source.

Synth_Gmag_Error
The uncertainty in the synthetic SDSS g-band magnitude of the optical counterpart to the X-ray source.

SDSS_Saturation_Flag
This parameter contains flags [0-2] indicating whether or not there is saturation in the SDSS for this source, where 0 means no and 1 or 2 means yes (see Section 5.3 of the reference paper).

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

Jmag_Error
The uncertainty in the 2MASS J-band magnitude.

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

JH_Color_Error
The uncertainty in the (J-H) color.

HK_Color
The (H-K_s) color of the 2MASS counterpart to the X-ray source.

HK_Color_Error
The uncertainty in the (H-K_s) color.


Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 16-Jan-2009