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Description
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 = 83<sup>o</sup> (26 Com), the other at b=-5<sup>o</sup> (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). This table was created by the HEASARC in April 2015 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/575/A42">CDS catalog J/A+A/575/A42</a> files table1.dat and table2.dat. This is a service provided by NASA HEASARC .
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