Sharp Chandra View of ROSAT All-Sky Survey Bright Sources I. Improvement of Positional Accuracy  

作　　者：Shuang Gao Song Wang Ji-Feng Liu 

机构地区：[1]Department of Astronomy, Beijing Normal University [2]Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences [3]College of Astronomy and Space Sciences, University of Chinese Academy of Sciences

出　　处：《Research in Astronomy and Astrophysics》2016年第12期67-74,共8页天文和天体物理学研究（英文版）

基　　金：supported by the National Natural Science Foundation of China (NSFC, Grant Nos. 11503002 and 11533002);the "Fundamental Research Funds for the Central Universities"

摘　　要：The ROSAT All-Sky Survey （RASS） represents one of the most complete and sensitive soft X- ray all-sky surveys to date. However, the deficient positional accuracy of the RASS Bright Source Catalog （BSC） and subsequent lack of firm optical identifications affect multi-wavelength studies of X-ray sources. The widely used positional errors σpos based on the Tycho Reference Catalog （Tycho-1） have previously been applied for identifying objects in the optical band. The considerably sharper Chandra view covers a fraction of RASS sources, whose ~rpos could be improved by utilizing the sub-arcsec positional accuracy of Chandra observations. We cross-match X-ray objects between the BSC and Chandra sources extracted from the Advanced CCD Imaging Spectrometer （ACIS） archival observations. A combined list of counter- parts （BSCxACIS） with Chandra spatial positions weighted by the X-ray flux of multiple counterparts is employed to evaluate and improve the former identifications of BSC when used with other surveys. Based on these identification evaluations, we suggest that the point-source likeness of BSC sources and INS （iso- lated neutron star） candidates should be carefully reconsidered.The ROSAT All-Sky Survey （RASS） represents one of the most complete and sensitive soft X- ray all-sky surveys to date. However, the deficient positional accuracy of the RASS Bright Source Catalog （BSC） and subsequent lack of firm optical identifications affect multi-wavelength studies of X-ray sources. The widely used positional errors σpos based on the Tycho Reference Catalog （Tycho-1） have previously been applied for identifying objects in the optical band. The considerably sharper Chandra view covers a fraction of RASS sources, whose ~rpos could be improved by utilizing the sub-arcsec positional accuracy of Chandra observations. We cross-match X-ray objects between the BSC and Chandra sources extracted from the Advanced CCD Imaging Spectrometer （ACIS） archival observations. A combined list of counter- parts （BSCxACIS） with Chandra spatial positions weighted by the X-ray flux of multiple counterparts is employed to evaluate and improve the former identifications of BSC when used with other surveys. Based on these identification evaluations, we suggest that the point-source likeness of BSC sources and INS （iso- lated neutron star） candidates should be carefully reconsidered.

关 键 词：catalogs -- surveys -- X-rays： general -- X-rays： stars 

分 类 号：P172.2[天文地球—天文学]