3,986 research outputs found

    Luminous supersoft X-ray emission from the recurrent nova U Scorpii

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    BeppoSAX detected luminous 0.2-2.0 keV supersoft X-ray emission from the recurrent nova U Sco ~19-20 days after the peak of the optical outburst in February 1999. U Sco is the first recurrent nova to be observed during a luminous supersoft X-ray phase. Non-LTE white dwarf atmosphere spectral models (together with a ~0.5 keV optically thin thermal component) were fitted to the BeppoSAX spectrum. We find that the fit is acceptable assuming enriched He and an enhanced N/C ratio. This implies that the CNO cycle was active during the outburst, in agreement with a thermonuclear runaway scenario. The best-fit temperature is ~9 10^5 K and the bolometric luminosity those predicted for steady nuclear burning on a WD close to the Chandrasekhar mass. The fact that U~Sco was detected as a supersoft X-ray source is consistent with steady nuclear burning continuing for at least one month after the outburst. This means that only a fraction of the previously accreted H and He was ejected during the outburst and that the WD can grow in mass, ultimately reaching the Chandrasekhar limit. This makes U~Sco a candidate type Ia supernova progenitor.Comment: 4 pages, accepted by A&A Letters 15 June 199

    China’s rise in a liberal world order in transition – introduction to the FORUM

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    In a time of great uncertainty about the future and resilience of the liberal world order this Forum focuses on China’s rise and interplay with the foundations of that liberal order. The key question is the extent to and variegated ways in which China - with its (re)ascendance to power and potential global leadership – is adapting to and perhaps even strengthening liberal institutions and rules of the game, confronting them, or developing alternative paths. In this introduction to the Forum we advance three key points based on the contributions. First, contrasting the orthodox binary scenarios of either inevitable conflict or co-optation offered in the mainstream IR debate, the Forum highlights the possibility of a third scenario of China’s interplay with the liberal world and its key actors, institutions, and rules. A hybrid and variegated scenario that entails both conflict and adaptation, differently entangled in different issue areas. Second, it stresses the need to conceptualize and empirically comprise the essentially interlinked nature of domestic state-society models and the global political economy. Third, we argue for a perspective that incorporates underlying economic and social structures and the power relations embedded therein
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