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ROSATRQQ: Help

ROSATRQQ - ROSAT Radio-Quiet Quasars Catalog


Overview

A sample of all radio-quiet quasars or quasars without radio detection taken from the Veron-Cetty - Veron catalog (1993, VERON93, ADC/CDS Cat. VII/166) which were either (i) detected by ROSAT in the ALL-SKY SURVEY (RASS, Voges 1992, in Proc. of the ISY Conference `Space Science', ESA ISY-3, ESA Publications, p.9, ADC/CDS Cat. IX/10), or (ii) detected as targets of pointed observations, or (iii) detected as serendipitous sources in pointed observations that were publicly available in the ROSAT point source catalog (ROSATSRC, Voges et al. 1995, ADC/CDS Cat. IX/11), has been compiled by Yuan et al. (1998, A&A, 330, 108). For all sources, they used the results of the Standard Analysis Software System (SASS, Voges et al. 1992, in Proc. of the ISY Conference `Space Science', ESA ISY-3, ESA Publications, p.223), employing the most recent processing for the Survey data (RASS-II, Voges et al. 1996, ADC/CDS Cat. IX/10). The total number of quasars in this ROSAT Radio-Quiet Quasars Catalog is 846.

Sixty-nine of the radio-quiet objects with radio detections have already been presented in a previous paper (Brinkmann, Yuan, and Siebert 1997, Cat. J/A+A/319/413) using the RASS-I results. Seventeen objects were found to be radio-loud from recent radio surveys and were marked in the table. When available, the power law photon indices and the corresponding absorption column densities (NH) were estimated from the two hardness ratios given by the SASS, both with free fitted NH and for Galactic absorption. The unabsorbed X-ray flux densities in the ROSAT band (0.1-2.4keV) were calculated from the count rates using the energy to counts conversion factor for power law spectra and Galactic absorption. The authors used as the photon index the value obtained for the individual source if the estimated 1-{sigma} error was smaller than 0.5, otherwise they used the redshift-dependent mean value (see the paper for details). Notice that the positions of sources in this catalog are not the positions of the X-ray sources, but the optical positions of the quasars as given in the VERON93 Catalog (Wolfgang Brinkmann, 1998 private communication).


Catalog Bibcode

1998A&A...330..108Y

References

Broad band energy distribution of ROSAT detected quasars. II. Radio-quiet objects Yuan W., Brinkmann W., Siebert J., Voges W. <Astron. Astrophys. 330, 108 (1998)>=1998A&A...330..108Y (SIMBAD/NED BibCode)

Provenance

This database was created by the HEASARC in December 1998, based on CDS/ADC Catalog J/A+A/330/108.

Parameters

IAU_Name
The IAU name or designation of the object, based on its B1950 equatorial co-ordinates.

RA
Right Ascension of the optical object in the selected equinox; this was given to the nearest tenth of a second of time in the original CDS/ADC catalog and in J2000 equinox.

Dec
Declination of the optical object in the selected equinox; this was given to the nearest arcsecond in the original CDS/ADC catalog and in J2000 equinox.

LII
The galactic longitude of the optical object.

BII
The galactic latitude of the optical object.

Type_Flag
A flag for classification and/or additional information about the object; the following values are used:


   type_flag value     Meaning

        S           The object was originally detected at another waveband
                    than the optical or UV, such as the X-ray or IR.
        R           The object has been found to be radio-loud in recent
                    radio surveys.
        U           In a few cases, there is more than one quasar within
                    60 arcseconds of the X-ray source; the most plausible
                    object (usually the closest) is listed and marked with
                    the value U to indicate the identification uncertainty.
        C           Objects for which the X-ray flux is obviously contaminated
                    by a nearby source (usually extended) are marked with
                    the value C.
  

Alt_Name
Alternate name from VERON93

Redshift
The redshift of the quasar, as taken from the VERON93 Catalog. Notice that a '0' in the third decimal place is mostly an artifact of the machine-readable version of that catalog and that the printed version should be consulted if the user needs to know the actual precision of such a value.

Appmag
The optical magnitude (often but not always in the Johnson V band), as taken from the VERON93 Catalog.

Fx
The unabsorbed X-ray flux density (in the 0.1 - 2.4keV bandpass), in units of erg/s/cm2 (or mW/m2).

Fx_Error
The error in the X-ray flux density estimated solely from the one-sigma statistical error in the count rate. Notice that for sources with a small number of counts (mostly those taken from the All-Sky Survey) the systematic errors can be of the order of 30 per cent. Furthermore, for strong sources the spectral fits often show that the assumed simple power law slope is an inappropriate representation of the spectrum. In both cases, the systematic spectral uncertainties can be considerably larger than the purely statistical errors given here, which should therefore be taken as lower limits to the actual uncertainties. pi_free = > The X-ray photon index, for the case of free-fitted hydrogen column density nH, obtained from a power law fit of the form C*E**(-pi_free) in the ROSAT energy band. A missing entry means that no reasonable spectral index could be obtained.

PI_Free
X-ray photon index (free nh)

PI_Free_Poserr
The positive error in the X-ray photon index for the case of free-fitted hydrogen column density nH. If no error is given, its value is unphysically large. pi_free_negerr = > The negative error in the X-ray photon index for the case of free-fitted hydrogen column density nH. If no error is given, its value is unphysically large.

PI_Free_Negerr
Negative error of photon index

NH
The fitted X-ray absorbing column density in units of cm-2. A missing entry means that no reasonable spectral index could be obtained.

NH_Poserr
The positive error in the fitted X-ray absorbing column density in units of cm-2. If no error is given, its value is unphysically large.

NH_Negerr
The negative error in the fitted X-ray absorbing column density in units of cm-2. If no error is given, its value is unphysically large. pi_gal = > The X-ray photon index, obtained under the assumption of a fixed Galactic absorption and from a power law fit of the form C*E**(-pi_gal) in the ROSAT energy band. The Galactic hydrogen column density nH values were obtained from the EXSAS environment and are based on an interpolation of data from Dickey and Lockman (1990, ARAA, 28, 215) and Stark et al. (1992, ApJS, 79, 77). A missing entry means that no reasonable spectral index could be obtained. pi_gal_poserr = > The positive error in the X-ray photon index for the case of assumed Galactic hydrogen column density nH. If no error is given, its value is unphysically large. pi_gal_negerr = > The negative error in the X-ray photon index for the case of assumed Galactic hydrogen column density nH. If no error is given, its value is unphysically large.

PI_Gal
X-ray photon index (galact nh)

PI_Gal_Poserr
Positive error of photon index

PI_Gal_Negerr
Negative error of photon index

NH_Gal
The assumed Galactic hydrogen column density, in units of cm-2. The Galactic hydrogen column density nH values were obtained from the EXSAS environment and are based on an interpolation of data from Dickey and Lockman (1990, ARAA, 28, 215) and Stark et al. (1992, ApJS, 79, 77).

Detection
This parameter give information on the X-ray detection: an 'S' indicates that the object was detected in the All-Sky Survey only, a 'P' indicates that the object was detected only in a pointed observation, and 'SP' indicates that the object was detected in both.

Ref_PI
If published data were available for an object, these results (mostly the spectral indices) were used if they were considered to be of superior quality. The references used in such cases are indicated in this field as follows:

      BJ: Bechtold J. et al., 1994AJ....108..374B
      LA: Laor A. et al., 1997ApJ...477...93L
      RD: Reimers D. et al., 1995A&A...296L..49R
      SN: Schartel N. et al., 1996, Cat. J/A+A/307/33
      UM: Ulrich M. et al., 1996ApJ...457...77U
      VC: Vignali C. et al., 1997MmSAI..68..141V
      WT: Wang T. et al., 1996, Cat. J/A+A/309/81
  

Class
The HEASARC browse classification for the radio source: we have set this to `Radio-Quiet Quasar' for all entries in this database, except for those entries with type_flag='R' which we have set to `Radio-Loud Quasar'.


Contact Person

Questions regarding the ROSATRQQ database table can be addressed to the HEASARC User Hotline.
If you have any problems, please consult the help page or mail ledas-help@star.le.ac.uk
 
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