Optical identifications of southern rosat EUV and soft X-ray sources |
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| Authors: | David A H Buckley Kazuhiro Sekiguchi Darragh O'Donoghue Walter W Wargau |
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| Institution: | (1) South African Astronomical Observatory, Observatory 7935, PO Box 9, Cape Town, South Africa;(2) Department of Astronomy, University of Cape Town, Rondebosch 7700, Cape Town, South Africa;(3) Department of Mathematics, Applied Mathematics and Astronomy University of South Africa, P.O. Box 392, 0001 Pretoria, South Africa |
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| Abstract: | This paper discusses the first all-sky surveys of cosmic extreme ultra-violet and soft X-ray sources, discovered by ROSAT. Details of the surveys are presented, with comparisons made to previous selected surveys in the X-ray regime. The subsequent optical identification programs are described, and the major results summarized. We then discuss the main classes of EUV emitters: active chromosphere stars and hot white dwarfs, and describe the importance of EUV observations in understanding the astrophysics of these objects. Many bright, and relatively nearby, sources have been identified as hitherto unrecognized active stars, representing the extremes in chromospheric and coronal activity, be it binary or age related. Many new hot DA white dwarfs have also been indentified, and the most exciting result in this area is the discovery that significant traces of heavier elements (e.g. C, N, O, Si, Fe and Al) exist in their atmospheres, substantially increasing their EUV opacities. The importance of hot white dwarfs as  standard candles in probing the local interstellar medium is also discussed. Miscellaneous counterparts (AGN, PNN, O-B stars and CVs) that make up the rest of the sample of EUV sources are also briefly mentioned. We finish with a discussion of the on-going ROSAT Galactic Plane Survey (RGPS) identification program. |
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| Keywords: | artificial satellites space probes - surveys - ultraviolet: general - catalogues - stars: activity atmospheres binaries white dwarfs |
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