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ROSNEPXRAY - ROSAT North Ecliptic Pole Survey X-Ray Source Catalog

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Overview

This table contains the ROSAT North Ecliptic Pole (NEP) Survey X-Ray Source Catalog. The sky around the NEP, at RA (J2000.0) = 18h00m00s, Declination (J2000.0) = +66d33'39", has the deepest exposure of the entire ROSAT All-Sky Survey (RASS). The NEP is an undistinguished region of moderate Galactic latitude, b = 29.8 degrees, and hence it is suitable for compiling statistical samples of both Galactic and extragalactic objects. The authors have made such a compilation in the 80.6 square degrees region surrounding the NEP. Their sample fully exploits the properties of the RASS, since the only criteria for inclusion are source position and significance, and it yields the deepest large solid angle contiguous sample of X-ray sources to date. They find 442 unique sources above a flux limit ~2 x 10^-14 ergs cm^-2 s^-1 in the 0.5-2.0 keV band. In this table, the X-ray properties of these sources as determined from the RASS are presented. These include positions, fluxes, spectral information in the form of hardness ratios, and angular sizes.

Catalog Bibcode

2006ApJS..162..304H

References

The ROSAT North Ecliptic Pole Survey: The X-Ray Catalog
    Henry, J.P., Mullis, C.R., Voges, W., Boehringer, H., Briel, U.G.,
    Gioia, I.M., Huchra, J.P.
   <Astrophys. J. Suppl. Ser. 162, 304 (2006)>
   =2006ApJS..162..304H

Provenance

This table was created by the HEASARC in February 2006 based on a machine-readable version of Table 4 in the above paper which was obtained from the electronic ApJ website.

Parameters

Name
The source name as given in the published paper, formed using the 'RX J' (for ROSAT X-ray source, J2000 position) and the position of the X-ray centroid, truncated to 0.1 minutes of time and 1 arcminute of declination.

Nep_Scan
The North Ecliptic Pole source number, being an internal source identification number.

RA
The Right Ascension of the centroid of the X-ray source in the selected equinox. This was given in J2000 coordinates and to a precision of 0.1 seconds of time in the original table.

Dec
The Declination of the centroid of the X-ray source in the selected equinox. This was given in J2000 coordinates and to a precision of 1 arcsecond in the original table.

LII
The Galactic Longitude of the X-ray centroid.

BII
The Galactic Latitude of the X-ray centroid.

Count_Rate
The net count rate of the X-ray source in the ROSAT PSPC 0.1-2.4 keV broad band (PHA channels 11-235) within a circular aperture of 5' radius, except for RX J1834.1+7057, where the radius is 6.5'. The rate is corrected for vignetting, i.e., it is larger than the net counts divided by the time that the source was in the PSPC field of view (FoV).

Count_Rate_Error
The 1-sigma error in the X-ray source count rate derived from the maximum-likelihood procedure described in Section 2.1 of the paper.

Exposure
The equivalent on-axis exposure time, in seconds (s). This is smaller than the time that the source was in the PSPC FoV, notice.

NH
The hydrogen column density, in cm^-2, from Elvis et al. (1994, ApJS, 95, 413), supplemented by Stark et al. (1992, ApJS, 79, 77). The column densities were linearly interpolated among the four pixels of the relevant map nearest to the X-ray position.

HR_1
The hardness ratio HR1 = (H-S)/(H+S), where H is the net counts in the 0.52-2.01 keV band (PHA channels 52-201), and S is the net counts in the 0.11-0.41 keV band (PHA channels 11-41). Negative net counts resulting from background subtraction have been set to zero, yielding hardness ratios between -1 and +1.

HR_1_Error
The 1-sigma error in the hardness ratio HR1.

HR_2
The hardness ratio HR2 = (H-S)/(H+S), where H is the net counts in the 0.91-2.01 keV band (PHA channels 91-201), and S is the net counts in the 0.52-0.90 keV band (PHA channels 52-90). Negative net counts resulting from background subtraction have been set to zero, yielding hardness ratios between -1 and +1.

HR_2_Error
The 1-sigma error in the hardness ratio HR2.

Source_Extent
The sigma of the source extent in arcseconds, approximating it by a Gaussian.

Likelihood_Diff
The difference in likelihoods between the best-fitting extended and point-source models of the source surface brightness, both measured as described in Section 2.1 of the paper.

Ml_Likelihood
The source existence likelihood from the maximum likelihood analysis in the broad band. The value has been set to 999 if it exceeds that value.

Mdetect_Likelihood
The source existence likelihood from the MDETECT analysis in the band for which the source has the highest existence likelihood. The value has been set to 999 if it exceeds that value.

Flux
The total observed unabsorbed flux, in units of erg/s/cm^2 and for the 0.5-2 keV band, obtained from the detect count rate. The spectra assumed are thermal with kT = 10^7 K for Galactic objects and that given by the value of spectral_parameter for galaxy groups and clusters. For extragalactic point sources, the spectra are power laws with photon indices of 2. Absorption for extragalactic objects is parameterized by the value of the nh parameter. The error in the flux may be scaled from the error in the count rate.

Lx
The total X-ray luminosity, in units of erg/s and for the 0.5-2 keV band in the rest frame, assuming a cosmology with a Hubble Constant of 70 km/s/Mpc, Omega_M0 = 0.3 and Omega_Lambda0 = 0.7, as obtained from the flux.

Source_Type
The optical identification class. The identification classes are 'STAR', 'CL' for galaxy group or cluster, 'AGN1' or 'AGN2' for active galactic nuclei based on the equivalent width of the emission lines and the broadness of the permitted emission lines as defined in Gioia et al. (2003, ApJS, 149, 29), 'BL' for BL Lac object, 'PN' for planetary nebula, and 'GAL' for a possibly interacting galaxy.

Redshift
The spectroscopic redshift, given for extragalactic objects.

Spectral_Parameter
The parameter of the unabsorbed spectrum: the temperature in keV or the photon index. This quantity varies for groups and clusters but is the same for all Galactic objects and for all extragalactic point sources, as described in Sections 2.3 and 2.4 of the paper, respectively. In particular, the unabsorbed spectrum for all Galactic sources is a Raymond-Smith thermal plasma model with solar abundances and a temperature of 10^7 K (0.9 keV). For all extragalactic point sources the spectrum is a power law with a photon index of 2.

Size_Correction
The size correction to convert the tabulated detect count rates to total count rates, as described in Section 2.4 of the paper. This quantity varies for groups and clusters but is the same for all Galactic objects and for all extragalactic point sources. In particular, the size correction is 1.0498 for all point sources.

Class
The HEASARC Browse object classification for the optical counterpart of the X-ray source, based on the value of the source_type parameter.


Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 23-Feb-2006