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XMMSSCLWBS - XMM-Newton 2XMMi-DR3 Selected Source Classifications Catalog

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Overview

The authors have carried out a classification of 4,330 X-ray sources in the 2XMMi-DR3 catalog. The sources were selected under the requirement of being a point source with multiple XMM-Newton observations and at least one detection with a signal-to-noise ratio larger than 20. For about one-third of the sources, the authors are able to obtain reliable source types from the literature. They mostly correspond to various types of stars (611), active galactic nuclei (AGNs, 753), and compact object systems (138) containing white dwarfs, neutron stars, and stellar-mass black holes. The authors find that about 99% of stars can be separated from other source types based on their low X-ray-to-IR flux ratios and frequent X-ray flares. AGNs have remarkably similar X-ray spectra, with the power-law photon index centered around 1.91 +/- 0.31, and their 0.2-4.5 keV flux long-term variation factors have a median of 1.48, with 98.5% being less than 10. In contrast, 70% of compact object systems can be very soft or hard, highly variable in X-rays, and/or have very large X-ray-to-IR flux ratios, separating them from AGNs. Using these results, the authors derive a source type classification scheme to classify the other sources and find 644 candidate stars, 1,376 candidate AGNs, and 202 candidate compact object systems, whose false identification probabilities are estimated to be about 1%, 3%, and 18%, respectively. There are still 320 sources associated with nearby galaxies and 151 in the Galactic plane, which the authors expect to be mostly compact object systems or background AGNs. There are also 100 candidate ultraluminous X-ray sources. They are found to be much less variable than other accreting compact objects.

Catalog Bibcode

2012ApJ...756...27L

References

Classification of X-Ray Sources in the XMM-Newton Serendipitous Source Catalog
     Lin D., Webb N.A., Barret D.
    <Astrophys. J. 756, 27 (2012)>
    =2012ApJ...756...27L

Provenance

This table was created by the HEASARC in October 2012 based on an electronic version of Table 4 from the reference paper which was obtained from the ApJ web site.

Parameters

SrcID
The 2XMMi-DR3 Catalog unique source identifier.

Name
The 2XMMi-DR3 source designation based on its J2000.0 equatorial coordinates, e.g., '2XMM J005412.9-373309', '2XMMi J170058.4-461107', etc.

RA
The mean Right Ascension of the X-ray source in the selected equinox. This was given in J2000.0 coordinates to a precision of 10-5 degrees (0.036 arcseconds) in the original table.

Dec
The mean Declination of the X-ray source in the selected equinox. This was given in J2000.0 coordinates to a precision of 10-5 degrees (0.036 arcseconds) in the original table.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Error_Radius
The mean uncertainty in the X-ray source position, in arcseconds.

NH_Gal
The Leiden/Argentine/Bonn Survey of Galactic HI column density in the direction of the source, in H atoms cm-2.

Num_Observations
The number of XMM-Newton observations which included the location of the X-ray source.

Time_Span_Observations
The time span of all of the XMM-Newton observations which included the location of the X-ray source.

Num_Detections
The number of detections of the X-ray source listed in the 2XMMi-DR3 Catalog.

Time_Span_Detections
The time span of all of the detections of the X-ray source listed in the 2XMMi-DR3 Catalog.

Object_Type
The source classification using the following schema:

     Star  = star, probably main-sequence star if object_type_rel = 'A';
     PrSt  = pre-main-sequence star;
     OrSr  = Orion variable star;
     VrSt  = variable star (probably eclipsing binary, rotationally variable
             or pulsating variable star);
     FlSt  = flaring star;
     Sy1n  = narrow-line Seyfert 1;
     Sy1   = Seyfert 1;
     Sy2   = Seyfert 2;
     LIN   = low-ionization nuclear emission-line region;
     Bla   = blazars;
     QSO   = quasi-stellar object/quasar;
     AGN   = active galactic nucleus;
     G     = galaxy;
     BHB   = black-hole X-ray binary;
     Bstr  = burster;
     aPsr  = accretion-powered X-ray pulsar;
     rPsr  = rotation-powered pulsar;
     INS   = thermally cooling isolated neutron star;
     MGR   = magnetar;
     CV    = cataclysmic variable;
     ULX   = ultra-luminous X-ray source;
     CO    = compact object system (containing a
             white dwarf/neutron star/stellar-mass black hole);
     XGS   = candidate non-nuclear extragalactic source;
     GPS   = source probably in the Galactic plane (|b|<=10 degree);
     SNR   = supernova remnant;
     Mixed = refer to ref_object_type for the detailed type.
  

Object_Type_Rel
The reliability of the object type:

         A=identified,
         B=candidate.
  

Ref_Object_Type
The relevant reference/bibcode for the source, mostly concerning its classification.

Alt_Name
The designation used for the source in the relevant reference, cf., the ref_object_type parameter value.

Alt_Object_Type
The object classification given for the source in the relevant reference, cf., the ref_object_type parameter value. For the meaning of the symbols used for this parameter, refer to the specified reference and/or the abbreviations listed above used in the object_type parameter.

Co_Class_Reasons
The authors have dubbed compact object systems as binaries containing either white dwarfs, i.e., cataclysmic variables, or neutron stars and black holes, i.e., X-ray binary systems. This parameter codes their reasons for classifying the specific X-ray source as a compact object system thus:

    Code  Meaning

      S = soft (HR1 < -0.4, HR2 < -0.5, HR3 < -0.7, or HR4 < -0.8)
      H = hard (-0.1 <HR3 < 0.5 and -0.25 < HR4 < 0.1)
      V = highly variable V_var(0.2-4.5 keV) > 10
      R = high X-ray-to-IR flux ratio (log(F_X/F_IR) > 2.5)
      E = non-nuclear extra-galactic
      G = in the Galactic plane (|b| < 10 degrees)
      L = literature, which includes more source properties such as dips
  

The hardness ratios are defined as HRi = (CRi+1 - CRi)/(CRi+1 + CRi) where CRi+1 and CRi are the MOS1-medium-filter equivalent count rates in the i+1 and i energy bands, respectively. The latter are defined as:

  Band Number   Energy Range (keV)

    1            0.2 - 0.5
    2            0.5 - 1.0
    3            1.0 - 2.0
    4            2.0 - 4.5
    5            4.5 - 12.0
    8            0.2 - 12.0
  

Log_Fx_Fo
The logarithm of the X-ray-to-optical flux ratio for the source. The lower limit to this parameter value is given in cases where there is no optical counterpart. The authors used the R2-band magnitude to define the optical flux as log (fo) = -R2/2.5 - 5.37, following Maccacaro et al. (1988, ApJ, 326, 680). In some cases when the R2-band magnitude was not available, the authors used the R1-band magnitude instead. For sources without optical counterparts, they assumed R2 = 21.0, which is about the minimum among the counterparts found and was taken as an upper limit. Throughout this study, all fluxes are in units of erg s-1 cm-2 and correspond to their apparent/absorbed values.

Log_Fx_Fir
The logarithm of the X-ray-to-infrared flux ratio for the source. The lower limit to this parameter value is given in cases where there is no infrared counterpart. The IR flux was calculated with the Ks-band magnitude from the 2MASS PSC, log (fir = -Ks/2.5 - 6.95, assuming the "in-band" zero-magnitude flux of the Ks band from Cohen et al. (2003, AJ, 126, 1090). For sources without IR counterparts, the authors calculated the upper limit using Ks = 15.3, the 3-sigma limiting sensitivity of this band in the 2MASS. Throughout this study, all fluxes are in units of erg s-1 cm-2 and correspond to their apparent/absorbed values.

Max_Flare_Bck_Ratio
The maximum value of the ratio of the flare peak to the persistent background flux value for stellar X-ray flaring sources. The procedure used by the authors to search for stellar X-ray flares is discussed in Appendix B of the reference paper.

ObsID_Flare
The XMM-Newton obsid (observation identification) for the observation in which the brightest flare was detected.

Max_Flux_1234
The maximum flux Fmax of the X-ray source in the 0.2 - 4.5 keV energy range (bands 1 through 4 inclusive), in erg cm-2 s-1. The procedure used by the authors to calculate X-ray fluxes is discussed in Section 2.2. of the reference paper. The authors only used detections with the flux above 4-sigma (four times the error) when calculating Fmax.

Max_Flux_1234_Error
The 1-sigma uncertainty in the maximum flux Fmax of the X-ray source in the 0.2 - 4.5 keV energy range (bands 1 through 4 inclusive), in erg cm-2 s-1.

ObsID_Max_Flux_1234
The XMM-Newton obsid (observation identification) for the observation in which the maximum flux in the 0.2 - 4.5 keV energy range was detected.

Min_Flux_1234
The minimum flux Fmin of the X-ray source in the 0.2 - 4.5 keV energy range (bands 1 through 4 inclusive), in erg cm-2 s-1. The procedure used by the authors to calculate X-ray fluxes is discussed in Section 2.2. of the reference paper. The authors used the 2 sigma value as the flux for detections below 2 sigma when calculating Fmin.

Min_Flux_1234_Error
The 1-sigma uncertainty in the minimum flux Fmin of the X-ray source in the 0.2 - 4.5 keV energy range (bands 1 through 4 inclusive), in erg cm-2 s-1.

ObsID_Min_Flux_1234
The XMM-Newton obsid (observation identification) for the observation in which the minimum flux in the 0.2 - 4.5 keV energy range was detected.

Flux_Var_Factor_1234
The long-term flux variation factor of the X-ray source in the 0.2 - 4.5 keV energy band, i.e., the ratio of the maximum to minimum fluxes Fmax/Fmin.

Sig_Var_Factor_1234
The significance of the long-term flux variability of the X-ray source in the 0.2 - 4.5 keV energy band, as defined in Section 2.3 and equation (2) of the reference paper.

Max_Flux_8
The maximum flux Fmax of the X-ray source in the 0.2 - 12.0 keV energy range (band 8), in erg cm-2 s-1. The procedure used by the authors to calculate X-ray fluxes is discussed in Section 2.2. of the reference paper. The authors only used detections with the flux above 4-sigma (four times the error) when calculating Fmax.

Max_Flux_8_Error
The 1-sigma uncertainty in the maximum flux Fmax of the X-ray source in the 0.2 - 12.0 keV energy range (band 8), in erg cm-2 s-1.

ObsID_Max_Flux_8
The XMM-Newton obsid (observation identification) for the observation in which the maximum flux in the 0.2 - 12.0 keV energy range was detected.

Min_Flux_8
The minimum flux Fmin of the X-ray source in the 0.2 - 12.0 keV energy range (band 8), in erg cm-2 s-1. The procedure used by the authors to calculate X-ray fluxes is discussed in Section 2.2. of the reference paper. The authors used the 2 sigma value as the flux for detections below 2 sigma when calculating Fmin.

Min_Flux_8_Error
The 1-sigma uncertainty in the minimum flux Fmin of the X-ray source in the 0.2 - 12.0 keV energy range (band 8), in erg cm-2 s-1.

ObsID_Min_Flux_8
The XMM-Newton obsid (observation identification) for the observation in which the minimum flux in the 0.2 - 12.0 keV energy range was detected.

Flux_Var_Factor_8
The long-term flux variation factor of the X-ray source in the 0.2 - 12.0 keV energy band, i.e., the ratio of the maximum to minimum fluxes Fmax/Fmin.

Sig_Var_Factor_8
The significance of the long-term flux variability of the X-ray source in the 0.2 - 12.0 keV energy band, as defined in Section 2.3 and equation (2) of the reference paper.

USNOB1_Name
The USNO-B1.0 designation of the optical counterpart to the X-ray source, selected to be the closest counterpart within 4 arcseconds in most cases.

XMM_USNOB1_Offset
The angular separation, in arcseconds, between the X-ray position and the USNO-B1.0 optical source position.

B1_Mag
The USNO-B1.0 B1 magnitude of the optical counterpart to the X-ray source.

R1_Mag
The USNO-B1.0 R1 magnitude of the optical counterpart to the X-ray source.

B2_Mag
The USNO-B1.0 B2 magnitude of the optical counterpart to the X-ray source

R2_Mag
The USNO-B1.0 R2 magnitude of the optical counterpart to the X-ray source.

Imag
The USNO-B1.0 I magnitude of the optical counterpart to the X-ray source.

Qual_USNOB1_Match
This flag parameter is set to 1 if the quality of the optical match to the X-ray source is considered to be bad, e.g., due to their coincidence with a bright globular cluster.

TwoMASS_Name
The 2MASS PSC designation of the infrared counterpart to the X-ray source, selected to be the closest counterpart within 4 arcseconds in most cases.

XMM_TwoMASS_Offset
The angular separation, in arcseconds, between the X-ray position and the 2MASS PSC infrared source position.

Jmag
The 2MASS J magnitude (1.2-micron) of the infrared counterpart to the X-ray source.

Jmag_Error
The mean error in the 2MASS J magnitude (1.2-micron) of the infrared counterpart to the X-ray source.

Hmag
The 2MASS H magnitude (1.6-micron) of the infrared counterpart to the X-ray source.

Hmag_Error
The mean error in the 2MASS H magnitude (1.6-micron) of the infrared counterpart to the X-ray source.

Ks_Mag
The 2MASS Ks magnitude (2.2-micron) of the infrared counterpart to the X-ray source.

Ks_Mag_Error
The mean error in the 2MASS Ks magnitude (2.2-micron) of the infrared counterpart to the X-ray source.

Qual_TwoMASS_Match
This flag parameter is set to 1 if the quality of the infrared match to the X-ray source is considered to be bad, e.g., due to their coincidence with the persistence artifact positions in the 2MASS, or with a bright globular cluster.

RC3_Galaxy_Name
The Third Reference Catalog of Galaxies (RC3: de Vaucouleurs et al. 1991) designation for the galaxy (if any) near the X-ray source position. X-ray sources found near such galaxies are considered by the authors to be candidate non-nuclear extragalactic sources if they are > 4 arcseconds from the galaxy center but within 2 R25, where R25 is the elliptical radius of the D25 isophotal ellipse in the direction from the galaxy center to the source.

RC3_RA
The Right Ascension of the center of the galaxy (if any) near the X-ray source position, in the selected equinox. This was taken by the authors from NED when possible, else from the RC3 Catalog. This was given in J2000.0 coordinates to a precision of 10-5 degrees (0.036 arcseconds) in the original table.

RC3_Dec
The Declination of the center of the galaxy (if any) near the X-ray source position, in the selected equinox. This was taken by the authors from NED when possible, else from the RC3 Catalog. This was given in J2000.0 coordinates to a precision of 10-5 degrees (0.036 arcseconds) in the original table.

XMM_RC3_Offset
The angular separation S, in arcseconds, between the X-ray position and the center of the RC3 matching galaxy.

XMM_RC3_Offset_D25
The ratio of the angular Separation S between the X-ray position and the center of the RC3 matching galaxy to R25, S/R25, where R25 is the elliptical radius of the D25 isophotal ellipse in the direction from the galaxy center to the source.

Galaxy_Distance
The distance to the galaxy near the X-ray source position, in megaparsecs (Mpc). The authors adopted the distances to most galaxies used in Liu and Bregman (2005, ApJS, 157, 59) and Liu (2011, ApJS, 192, 10). For 17 other galaxies, they obtained their distances using the redshifts from NED and assuming a flat universe with the Hubble constant H0 = 75 km s-1 Mpc-1 and a matter density OmegaM = 0.27 if they have recessional velocities larger than 1000 km s-1, or from the literature otherwise.

Lx_Max
The maximum 0.2-12.0 keV absorbed luminosity of the source, for candidate non-nuclear extragalactic sources, calculated assuming the source is at the same distance as the nearby RC3 galaxy

Class
The HEASARC Browse object classification of the source, based on the object_type parameter value. The categories in the latter do not exactly match the categories used in the HEASARC classification scheme, so some approximations were necessary, e.g., all objects classified with object types of 'CO' (compact object systems) or 'XGS' (candidate non-nuclear extragalactic sources) have been given the HEASARC class of X-ray binary.


Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 22-Oct-2012