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RASS2FXRAY - ROSAT All-Sky Survey Two Selected Fields X-Ray Source Catalog

HEASARC
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Overview

The optical identification of large number of X-ray sources such as those from the ROSAT All-Sky Survey is challenging with conventional spectroscopic follow-up observations. The authors have investigated two ROSAT All-Sky Survey fields of size 10 degrees by 10 degrees each, one at a galactic latitude b = 83o (26 Com), the other at b=-5o (gamma Sge), in order to optically identify the majority of sources. They used optical variability, among other more standard methods, as a means of identifying a large number of ROSAT All- Sky Survey sources. All objects fainter than about 12th magnitude and brighter than about 17th magnitude in or near the error circle of the ROSAT positions were tested for optical variability on hundreds of archival plates of the Sonneberg field patrol.

The reference paper contains probable optical identifications of altogether 256 of the 370 ROSAT sources analyzed. In particular, the authors found 126 active galactic nuclei (some of them may be misclassified cataclysmic variables, CVs), 17 likely clusters of galaxies, 16 eruptive double stars (mostly CVs), 43 chromospherically active stars, 65 stars brighter than about 13th magnitude, 7 UV Ceti stars, 3 semi-regular or slow irregular variable stars of late spectral type, 2 DA white dwarfs, 1 Am star, 1 supernova remnant, and 1 planetary nebula. As expected, nearly all active galactic nuclei are found in the high-galactic latitude field, while the majority of CVs is located at low galactic latitudes. The authors identify in total 72 new variable objects. X-ray emission is, not unexpectedly, tightly correlated with optical variability, and thus their new method for optically identifying X-ray sources is demonstrated to be feasible. Given the large number of optical plates used, this method was most likely not more efficient than, for example, optical spectroscopy. However, it required no telescope time, only access to archival data.

This table contains the X-ray properties of the 370 ROSAT point sources found by the authors in the 2 fields that they examined above a maximum likelihood threshold of 8. It is essentially the union of the 238 sources which were listed in Table 1 (26 Com field) of the reference paper with the 132 sources listed in Table 2 (gamma Sge field) of that paper. Notice that the source detection criterion for the ROSAT All-Sky Survey (RASS: 1RXS Catalog) had a slightly higher threshold of 10, so that the present source list is more extensive than the 1RXS Catalog source list in these two areas. The lists of the optical counterparts to these X-ray sources and their spectroscopic and photometric properties which were given in Table 8 (26 Com field) of the reference paper and Table 9 (gamma Sge field) of that paper are available in the HEASARC table RASS2FOID (to which the present table is linked).


Catalog Bibcode

2015A&A...575A..42G

References

Optical counterparts of ROSAT X-ray sources in two selected fields at
low vs. high Galactic latitudes.
    Greiner J., Richter G.A.
    <Astron. Astrophys. 575, A42 (2015)>
    =2015A&A...575A..42G        (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in April 2015 based on CDS catalog J/A+A/575/A42 files table1.dat and table2.dat.

Parameters

Source_Number
A unique identification number for each X-ray source in the catalog. In the original two tables, the source numbers were unique within each table but are not when combined, as they are in the present HEASARC version. To break this degeneracy, the HEASARC has created a unique source number by adding 1000 to the original Table 1 (26 Com field) source number values and 2000 to the original Table 2 (gamma Sge field) source number values.

Name
The source name created by the HEASARC in the style recommended by the Dictionary of Nomenclature of Celestial Objects, viz., the prefix '[GR2015] Com' for the sources in the 26 Com field or the prefix '[GR2015] Sge' for the sources in the gamma Sge field (where GR2015 stands for Greiner, Richter 2015) combined with the original source numbers from Tables 1 and 2 of the reference paper. Thus the first source in Table 1 of the reference paper has been named '[GR2015] Com 1' in this HEASARC table (and been given the unique source number of 1001 herein) and the 132nd source in Table 2 of that paper has been named '[GR2015] Sge 132' in this HEASARC table (and been given the unique source number of 2132 herein).

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

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

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

RASS_Name
The ROSAT All-Sky Survey (1RXS) source designation of the X-ray source, if listed therein, in the usual style, e.g., '1RXS J123356.4+260249'.

RASS_Error_Radius
The positional uncertainty of the RASS source, in arcseconds, i.e., the 90%-confidence statistical error.

Count_Rate
The vignetting-corrected ROSAT PSPC count rate of the X-ray source, in counts per second.

Hardness_Ratio_1
The X-ray spectral shape of the X-ray source, expressed in terms of the hardness ratios HR1. The hardness ratio HR1 is defined as the normalized count difference (N50-200 - N10-40)/(N10-40 + N50-200), where Na-b denotes the number of counts in the PSPC between channels a and b. HR1 is sensitive to the Galactic foreground absorbing column density.

Hardness_Ratio_1_Error
The uncertainty in the hardness ratio HR1 of the X-ray source.

Hardness_Ratio_2
The X-ray spectral shape of the X-ray source, expressed in terms of the hardness ratios HR2. The hardness ratio HR2 is defined as the normalized count difference (N91-200 - N50-90)/(N50-200), where Na-b denotes the number of counts in the PSPC between channels a and b.

Hardness_Ratio_2_Error
The uncertainty in the hardness ratio HR2 of the X-ray source.

Flux
The observed (not extinction corrected!) X-ray flux of the X-ray source in the 0.1 - 2.4 keV band, in units of erg/cm2/s. This is a gross underestimate for objects identified as clusters of galaxies (or candidates), as this is derived from point-source PSF-fitting.

Ctrpart_ID
The most likely optical identification of the X-ray source according to various criteria as discussed in the reference paper. These are letter codes a, b., etc., referring to all optical objects inside or near the error circle radius of about 30 arcseconds centered on the ROSAT position. The properties of these optical counterparts are given in the HEASARC table RASS2FOI (q.v.). If there is no such optical object (ctrpart_note = '--'), this field is left blank; it is also left blank for the 7 "sources" in the Sge field which are actually detections of flux enhancements of an extended supernova remnant (ctrpart_note = 'SNR') and for the 17 "sources" in the Com field which are cases where the X-ray emission is more likely associated with the galaxy cluster gas emission rather than with individual galaxies in that cluster (ctrpart_note = 'Cluster' or 'Cluster?').

Ctrpart_Note
This parameter contains comments on the optical counterpart of the X-ray source, as follows:

    Value   Meaning

   Cluster  one of the 17 "sources" in the Com field which are cases where the
            X-ray emission is more likely associated with the galaxy cluster
            gas emission rather than with individual galaxies in that cluster;
   SNR      One of  7 "sources" in the Sge field which are actually detections
            of flux enhancements of an extended supernova remnant;
   --       This means that no optical identification can be proposed;
   ?        A question mark by itself or after another symbol denotes some
            doubts concerning the identification due to inconclusive data or to
            other alternatives.
  

Contact Person

Questions regarding the RASS2FXRAY database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 1-May-2015