X-ray observations of 4 Draconis: symbiotic binary or cataclysmic triple? |
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Authors: | Peter J Wheatley Koji Mukai † Domitilla de Martino |
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Institution: | Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH;Laboratory for High Energy Astrophysics, NASA/GSFC, Code 662, Greenbelt, MD 20771, USA;INAF–Osservatorio Astronomico di Capodimonte, via Moiariello n. 16, I-80131 Napoli, Italy |
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Abstract: | We present the first X-ray observations of the 4 Draconis system, consisting of an M3 III giant with a hot ultraviolet companion. It has been claimed that the companion is itself an AM Her-type binary system, an identification that places strong constraints on the evolution of cataclysmic variables. We find that the X-ray properties of 4 Draconis are consistent with the presence of an accreting white dwarf, but not consistent with the presence of an AM Her system. We conclude that 4 Draconis is therefore most likely a symbiotic binary containing a white dwarf accreting material from the wind of the red giant. The X-ray spectrum of 4 Draconis is sometimes dominated by partially ionized photoelectric absorption, presumably due to the wind of the red giant. We note that X-ray monitoring of such systems would provide a powerful probe of the wind and mass-loss rate of the giant, and would allow a detailed test of wind accretion models. |
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Keywords: | accretion accretion discs binaries: close stars: individual: 4 Draconis novae cataclysmic variables white dwarfs X-rays: stars |
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