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ROSATHARD - ROSAT Hard-Spectrum X-Ray Source Catalog

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Overview

This table contains a catalog of 147 serendipitous X-ray sources selected to have hard spectra (spectral indices Alpha < 0.5) from a survey of 188 ROSAT fields. Such sources must be the dominant contributors to the X-ray background at faint fluxes. The authors have used Monte Carlo simulations to verify that their technique is very efficient at selecting hard sources: the survey has >= 10 times as much effective area for hard sources as it has for soft sources above a 0.5 - 2 keV flux level of 10-14 erg cm-2 s-1. The distribution of best-fitting spectral slopes of the hard sources suggests that a typical ROSAT hard source in this survey has a spectral slope Alpha ~ 0. The hard sources have a steep number-flux relation (dN/dS ~ _S-Gamma, with a best-fitting value of Gamma = 2.72 +/- 0.12), and make up about 15% of all 0.5 - 2 keV sources with S > 10-14 erg cm-2 s-1. If their N(S) continues to fainter fluxes, the hard sources will comprise ~ 40% of sources with 5 x 10-15 < S < 10-14 erg cm-2 s-1. The population of hard sources can therefore account for the harder average spectra of ROSAT sources with S < 10-14erg cm-2 s-1. They probably make a strong contribution to the X-ray background at faint fluxes and could be the solution to the X-ray background spectral paradox.

Catalog Bibcode

2000MNRAS.318.1073P

References

A survey of hard spectrum ROSAT sources - I. X-ray source catalogue.
    Page M.J., Mittaz J.P.D., Carrera F.J.
   <Mon. Not. R. Astron. Soc. 318, 1073 (2000)>
   =2000MNRAS.318.1073P

Provenance

This table was created by the HEASARC in March 2012 based on CDS Catalog J/MNRAS/318/1073 file table2.dat, the ROSAT hard X-ray source catalog.

Parameters

Name
The source name based on the J2000.0 equatorial coordinates of the ROSAT source from the Starlink PSS source searching routine in the style recommended by the CDS Dictionary of Nomenclature of Celestial Objects for X-ray sources in this catalog, viz., '[PMC2000] RX JHHMMSS.ss+DDMMSS.s', where the prefix stands for 'Page, Mittaz, Carrera 2000 ROSAT X-ray' source.

SeqID
The ROSAT observation sequence identification (ROR) number in which the source was detected. The full list of 188 ROSAT PSPC fields which were searched by the authors is given in Table 1 of the reference paper.

RA
The Right Ascension of the ROSAT X-ray source in the selected equinox. This was implicitly given in the reference paper in the name of the source, which was based on its J2000 coordinates given to a precision of 0.01 seconds of time in RA.

Dec
The Declination of the ROSAT X-ray source in the selected equinox. This was implicitly given in the reference paper in the name of the source, which was based on its J2000 coordinates given to a precision of 0.1 arcseconds in Dec.

LII
The Galactic Longitude of the ROSAT X-ray source.

BII
The Galactic Latitude of the ROSAT X-ray source.

Exposure
The ROSAT PSPC exposure time at the location of the ROSAT X-ray source, after good time screening, in seconds (given in ks in the original table).

Off_Axis
The off-axis angle of the ROSAT X-ray source from the nominal pointing direction, in arcminutes.

Error_Radius
The positional uncertainty of the ROSAT X-ray source from the Starlink PSS source searching routine, in arcseconds.

SNR
The significance of the ROSAT X-ray source above the background level from the Starlink PSS source searching routine, in units of sigma. The PSS criterion included sources more than 4 sigma above the background.

PSF_Reduced_Chi_Squared
The reduced chi-squared, Chi2nu, (where nu = 11) from a fit of the model PSPC point spread function appropriate for the source off-axis angle to the source radial profile in 5-arcsecond bins out to 1 arcminute. This thus is a measure of whether or not the source is point-like.

Extraction_Radius
The size of the source circle radius used to extract the three-color spectrum, on arcseconds. (See Section 2.3 of the reference paper for more details).

SB_Counts
The number of counts in the PSPC channels 11 - 41 (energy band of 0.1 - 0.4 keV) within the source extraction circle.

MB_Counts
The number of counts in the PSPC channels 52 - 90 (energy band of 0.5 - 0.9 keV) within the source extraction circle.

HB_Counts
The number of counts in the PSPC channels 91 - 201 (energy band of 0.9 - 2.0 keV) within the source extraction circle.

SB_Bck_Counts
The predicted number of background counts in the PSPC channels 11 - 41 within the source extraction circle.

MB_Bck_Counts
The predicted number of background counts in the PSPC channels 52 - 90 within the source extraction circle.

HB_Bck_Counts
The predicted number of background counts in the PSPC channels 91 - 201 within the source extraction circle.

Spectral_Index
The fitted power-law spectral slope Alpha for the X-ray source, calculated as described in Section 2.4 of the reference paper. The exact criterion for inclusion of a source in this catalog (discussed in Section 3 of the reference paper) is Alpha + eU(Alpha) < 0.5, the value assumed by the authors for the slope of the extragalactic background, where eU(Alpha) is the 68% positive uncertainty in Alpha.

Spectral_Index_Pos_Err
The positive 68% uncertainty eU(Alpha) in the fitted power-law spectral slope Alpha.

Spectral_Index_Neg_Err
The negative 68% uncertainty eL(Alpha) in the fitted power-law spectral slope Alpha.

Hard_Spectral_Prob
The probability that the ROSAT hource has a spectral slope Alpha less (harder) than 0.5. (See Section 3 of the reference paper for more details).

Flux
The fitted 0.5 - 2 keV flux of the ROSAT source, in erg cm-2 s-1, assuming a power-law model and the Galactic absorption.

Flux_Pos_Err
The positive 68% uncertainty in the fitted 0.5 - 2 keV flux of the ROSAT source, in erg cm-2 s-1.

Flux_Neg_Err
The negative 68% uncertainty in the fitted 0.5 - 2 keV flux of the ROSAT source, in erg cm-2 s-1.

Optical_Ctrprt_Flag
This parameter flags whether the authors consider that the source has a likely optical counterpart and would be used in subsequent papers about optical spectroscopy and imaging of these hard sources: 'S' means that the source is suitable for optical spectroscopy, while 'I' means that the authors consider the source to be only suitable for imaging follow-up.


Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 23-Mar-2012