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SMCPSCXMM - Small Magellanic Cloud XMM-Newton Point Source Catalog

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Overview

The XMM-Newton survey of the Small Magellanic Cloud (SMC) yielded complete coverage of the bar and eastern wing in the 0.2-12.0 keV energy band. In addition to the main-field (5.58 deg2), available outer fields were included in the catalogue, yielding a total field area of 6.32 deg2. This catalog comprises 3,053 unique X-ray point sources and sources with moderate extent that have been reduced from 5,236 individual detections found in 100 observations between April 2000 and April 2010 (the details of these exposures are given in Table B.1 of the reference paper). For 927 sources, there were detections at multiple epochs, with some SMC fields observed up to 36 times. The detected sources have a median position uncertainty of 1.3 arcseconds (1 sigma) and limiting fluxes down to ~1 x 10-14 erg/s/cm2 in the 0.2-4.5 keV band, corresponding to X-ray luminosities of ~5 x 1033 erg/s for sources located in the SMC. Sources have been classified using X-ray hardness ratios, X-ray variability, and their multi-wavelength properties. In their paper, the authors discuss the statistical properties of the detected X-ray sources, like the spatial distribution, X-ray color diagrams, luminosity functions, and time variability. They have identified 49 SMC high-mass X-ray binaries (HMXB), four super-soft X-ray sources (SSS), 34 foreground stars, and 72 active galactic nuclei (AGN) behind the SMC. In addition, they found candidates for SMC HMXBs (45) and faint SSSs (8) as well as AGN (2092) and galaxy clusters (13).

Notice that X-ray sources with high extent (>40 arcseconds), e.g. supernova remnants and galaxy clusters, have been previously presented by Haberl et al. (2012, A&A, 545, A128) and are not included in this table.

To investigate the spectral behavior of all sources, the authors used hardness ratios HRi (i = 1, 2, 3, 4), defined by HRi = (Ri+1 - Ri)/(Ri+1 + Ri), where Ri is the count rate in energy band i as defined by:

   Band    Energy Range

    1       0.2-0.5 keV
    2       0.5-1.0 keV
    3       1.0-2.0 keV
    4       2.0-4.5 keV
    5       4.5-12. keV
To increase statistics, the authors also calculated average HR_is, combining all available instruments and observations. HRi is not given if both rates Ri and Ri+1 are null or if the 1-sigma uncertainty of Delta(HRi) covers the complete HR interval from -1 to +1. To convert an individual count rate Ri of an energy band i into a setup-independent, observed flux Fi, the authors calculated energy conversion factors (ECFs) fi = Ri/Fi , as described in Sect. A.3 of the reference paper. For the calculation, they assumed a universal spectrum for all sources, described by a power-law model with a photon index of 1.7 and a photo-electric foreground absorption by the Galaxy of NH,Gal = 6 x 1020 cm-2 (average for the SMC main field in the H I map of Dickey & Lockman 1990, ARAA, 28, 215).

In addition to the fluxes for each detection, the authors calculated flux upper limits FUL for each observation and source, if the source was observed but not detected in an individual observation. As for the initial source detection, they used the emldetect task to fit sources, but kept the source positions fixed at the master positions and accepted all detection likelihoods in order to get an upper limit for the flux.


Catalog Bibcode

2013A&A...558A...3S

References

The XMM-Newton survey of the Small Magellanic Cloud:
The X-ray point-source catalogue.
    Sturm R., Haberl F., Pietsch W., Ballet J., Hatzidimitriou D.,
    Buckley D.A.H., Coe M., Ehle M., Filipovic M.D., La Palombara N., Tiengo A.
    <Astron. Astrophys. 558, A3 (2013)>
    =2013A&A...558A...3S        (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in October 2013 based on CDS Catalog J/A+A/558/A3 file smc_src.dat.

Parameters

Source_Number
A unique source number for each X-ray source in the catalog. Note that this is not continuous or ordered by position.

Name
The X-ray source designation based on the J2000.0 source coordinates and using the 'XMMU' prefix for 'unregistered' (non-project) XMM-Newton sources, e.g., 'XMMU JHHMMSS.s+DDMMSS'.

Num_Detections
The number of detections of the source.

Num_Observations
The number of observations in which the source was in the XMM-Newton field of view.

Detection_Likelihood
The combined maximum detection likelihood MLdet of the source, normalized for two degrees of freedom. As in the case of the 2XMM Catalogue of Watson et al. (2009, A&A, 493, 339), the authors accepted detections with MLdet = -ln(P) >= 6, where P is the chance detection probability due to Poissonian background fluctuations. In Section 4.2 of the reference paper, the authors estimate that roughly 100 of the 418 sources in the catalog with MLdet < 8 are spurious, i.e., there is about 1 spurious source per observation.

RA
The astrometrically-corrected Right Ascension of the X-ray source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10-6 degrees in the original table. The astrometric corrections which were applied are discussed in Section A.2 of the reference paper and listed for each observation in Table B.1 (ibid.). Master source positions and source extents were calculated from the error-weighted average of the individual detection values.

Dec
The astrometrically-corrected Declination of the X-ray source in the selected equinox. This was given in J2000.0 decimal degrees to a precision of 10-6 degrees in the original table. The astrometric corrections which were applied are discussed in Section A.2 of the reference paper and listed for each observation in Table B.1 (ibid.). Master source positions and source extents were calculated from the error-weighted average of the individual detection values.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Error_Radius
The positional uncertainty of the X-ray source at the 1-sigma confidence level, in arcseconds (99.7% of all true source positions are expected to be within a radius of 3.439 sigma).

Flux_1
The average flux of the X-ray source in the standard XMM-Newton energy band 1, i.e., 0.2-0.5 keV, in erg cm-2 s-1.

Flux_1_Error
The uncertainty in the corresponding band average flux of the X-ray source, in erg cm-2 s-1.

Flux_2
The average flux of the X-ray source in the standard XMM-Newton energy band 2, i.e., 0.5-1.0 keV, in erg cm-2 s-1.

Flux_2_Error
The uncertainty in the corresponding band average flux of the X-ray source, in erg cm-2 s-1.

Flux_3
The average flux of the X-ray source in the standard XMM-Newton energy band 3, i.e., 1.0-2.0 keV, in erg cm-2 s-1.

Flux_3_Error
The uncertainty in the corresponding band average flux of the X-ray source, in erg cm-2 s-1.

Flux_4
The average flux of the X-ray source in the standard XMM-Newton energy band 4, i.e., 2.0-4.5 keV, in erg cm-2 s-1.

Flux_4_Error
The uncertainty in the corresponding band average flux of the X-ray source, in erg cm-2 s-1.

Flux_5
The average flux of the X-ray source in the standard XMM-Newton energy band 5, i.e., 4.5-12.0 keV, in erg cm-2 s-1.

Flux_5_Error
The uncertainty in the corresponding band average flux of the X-ray source, in erg cm-2 s-1.

Flux_Tot
The average flux of the X-ray source in the entire XMM-Newton energy range, i.e., 0.2-12.0 keV, in erg cm-2 s-1.

Flux_Tot_Error
The uncertainty in the average flux of the X-ray source in the entire XMM-Newton energy range, i.e., 0.2-12.0 keV, in erg cm-2 s-1.

Flux_1_To_4
The average flux of the X-ray source in the range encompassing the standard XMM-Newton energy ranges 1, 2, 3 and 4, i.e., 0.2-4.5 keV, in erg cm-2 s-1. Note that in the reference paper this range is described as the XMM-Newton XID band, but the latter is usually considered to be the union of the standard XMM-Newton energy ranges 2, 3 and 4, i.e., 0.5-4.5 keV,

Flux_1_To_4_Error
The uncertainty in the average flux of the X-ray source in the energy range from 0.2-4.5 keV, in erg cm-2 s-1.

Max_Flux_1_To_4
The maximum F_max_of all the measured 0.2-4.5 keV fluxes of the X-ray source in all of the observations in which it was included, in erg cm-2 s-1. See Section 3.2 of the reference paper for more details.

Max_Flux_1_To_4_Error
The uncertainty in the maximum of all the measured 0.2-4.5 keV fluxes of the X-ray source in all of the observations in which it was included, in erg cm-2 s-1.

Min_Flux_1_To_4
The minimum F_min_of all the measured 0.2-4.5 keV fluxes of the X-ray source in all of the observations in which it was included (or 3-sigma upper limit thereof if the latter were lower than the lowest detected flux), in erg cm-2 s-1. See Section 3.2 of the reference paper for more details.

Min_Flux_1_To_4_Error
The error in the minimum F_min_of all the measured 0.2-4.5 keV fluxes of the X-ray source in all of the observations in which it was included (or 3-sigma upper limit thereof if the latter were lower than the lowest detected flux), in erg cm-2 s-1.

HR1
The hardness ratio HR1 of the X-ray source over the energy range covered by the standard XMM-Newton bands 1 and 2. This is defined in the Overview above.

HR1_Error
The uncertainty in the hardness ratio HR1 of the X-ray source over the energy range covered by the standard XMM-Newton bands 1 and 2.

HR2
The hardness ratio HR2 of the X-ray source over the energy range covered by the standard XMM-Newton bands 2 and 3. This is defined in the Overview above.

HR2_Error
The uncertainty in the hardness ratio HR2 of the X-ray source over the energy range covered by the standard XMM-Newton bands 2 and 3.

HR3
The hardness ratio HR3 of the X-ray source over the energy range covered by the standard XMM-Newton bands 3 and 4. This is defined in the Overview above.

HR3_Error
The uncertainty in the hardness ratio HR3 of the X-ray source over the energy range covered by the standard XMM-Newton bands 3 and 4.

HR4
The hardness ratio HR4 of the X-ray source over the energy range covered by the standard XMM-Newton bands 4 and 5. This is defined in the Overview above.

HR4_Error
The uncertainty in the hardness ratio HR4 of the X-ray source over the energy range covered by the standard XMM-Newton bands 4 and 5.

Extent
The averaged source extent in the total energy range, in arcseconds. Master source positions and source extents were calculated from the error-weighted average of the individual detection values. Possible source extension was investigated by using a beta-model that approximated the brightness profile of galaxy clusters (Cavaliere and Fusco-Femiano 1976, A&A, 49, 137).

Extent_Error
The uncertainty in the averaged source extent in the total energy range, in arcseconds.

Extent_Likelihood
The likelihood statistic that the source is really extended

Ks_Prob_Constant
The probability Cst that the X-ray source was constant within the period covered by the observation as estimated using the Kolmogorov-Smirnov (KS) test to compare the photon arrival time distribution with the expected distribution from a constant source. This method is also applicable to sources with poor statistics, where background subtracted binned light curves cannot be obtained. A detailed description is given in Sect. A.4 of the reference paper. Notice that this source was applied for each observation in which the source was detected for sources with multiple detections. The value listed here is the minimum value of Cst among the individual detections.

Var_Factor
The variability V of the X-ray source in the 0.2-4.5 keV energy range defined as the ratio of the maximum over the minimum flux in this band among the various observations that covered the position of the source. This is thus a measure of the source variability between XMM-Newton observations. See Section 3.2 of the reference paper for more details.

Var_Significance
The significance S of the inter-observation variability V of the X-ray source in the 0.2-4.5 keV energy range as defined in Section 3.2 of the reference paper.

Broad_Type
The classification of the X-ray source using the following schema (uncertain cases are marked with question marks '?'):

       fg-star  = foreground star
      <fg-star> = candidate foreground star
       HMXB     = high-mass X-ray binary in the SMC
      <HMXB>    = candidate high-mass X-ray binary in the SMC
       AGN      = active galactic nucleus
      <AGN>     = AGN candidate counterparts based on (see Sect. 6.4.2 of paper):
                   radio (r),
                   Chandra X-ray source (x),
                   infrared (i),
                   optical (o), the latter being uncertain
       galaxy   = galaxy
       Cl*      = star cluster
       INS      = isolated neutron star
       PWN      = pulsar wind nebula
       MQ       = microquasar
       SMC-star = star in the SMC
       SSS      = supersoft X-ray source
      <SSS>     = candidate supersoft X-ray source
       AXP      = anomalous X-ray pulsar
       ClG      = galaxy cluster
  

Alt_Name
The name of the X-ray source, if previously identified.

Class
The HEASARC Browse object classification based on the broad_type parameter value.


Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 24-Oct-2013