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An X-ray-emitting blast wave from the recurrent nova RS Ophiuchi


Stellar explosions such as novae and supernovae produce most of the heavy elements in the Universe. The onset of a nova is well understood1 as driven by runaway thermonuclear fusion reactions on the surface of a white dwarf in a binary star system; but the structure, dynamics and mass of the ejecta are not well known. In rare cases, the white dwarf is embedded in the wind nebula of a red-giant companion, and the explosion products plough through the nebula and produce X-ray emission. Here we report X-ray observations of such an event, from the eruption of the recurrent nova RS Ophiuchi2,3. The hard X-ray emission from RS Ophiuchi early in the eruption emanates from behind a blast wave, or outward-moving shock wave, that expanded freely for less than 2 days and then decelerated owing to interaction with the nebula. The X-rays faded rapidly, suggesting that the blast wave deviates from the standard spherical shell structure4,5,6. The early onset of deceleration indicates that the ejected shell had a low mass, the white dwarf has a high mass7, and that RS Ophiuchi is therefore a progenitor of the type of supernova (type Ia) integral to studies of the expansion of the Universe.

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Figure 1: X-ray spectra from the first 3 weeks of the 2006 outburst of RS Oph.
Figure 2: X-ray flux and post-shock plasma temperature as a function of time.


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We are grateful for discussions with J. Raymond, C. Rakowski, M. Wood-Vasey and C. Matzner. J.L.S. acknowledges support from the NSF. G.J.M.L. acknowledges support from NASA, and from CNPq and FAPESP (Brazil).

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Sokoloski, J., Luna, G., Mukai, K. et al. An X-ray-emitting blast wave from the recurrent nova RS Ophiuchi. Nature 442, 276–278 (2006).

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