Early Spectroscopy of the 2010 Outburst of U Scorpii

Abstract

We present early spectroscopy of the recurrent nova U~Sco during the outburst in 2010. We successfully obtained time-series spectra at $t_{\mathrm{d}}=$0.37--0.44~d, where $t_{\mathrm{d}}$ denotes the time from the discovery of the present outburst. This is the first time-resolved spectroscopy on the first night of U Sco outbursts. At $t_{\mathrm{d}}\sim 0.4$~d the H$\alpha$ line consists of a blue-shifted ($-5000$ km s${}^{-1}$) narrow absorption component and a wide emission component having triple peaks, a blue ($\sim -3000$ km s${}^{-1}$), a central ($\sim 0$ km s${}^{-1}$) and a red ($\sim +3000$ km s${}^{-1}$) ones. The blue and red peaks developed more rapidly than the central one during the first night. This rapid variation would be caused by the growth of aspherical wind produced during the earliest stage of the outburst. At $t_{\mathrm{d}}=1.4$~d the H$\alpha$ line has a nearly flat-topped profile with weak blue and red peaks at $\sim \pm 3000$ km s${}^{-1}$. This profile can be attributed to a nearly spherical shell, while the asphericity growing on the first night still remains. The wind asphericity is less significant after $t_{\mathrm{d}}=9$ d.

arXiv comment5 pages, 3 figures, Accepted for publication of PASJ Letters

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• Young and Massive Binary Progenitors of Type Ia Supernovae and Their Circumstellar Matter
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• U Sco 2010 outburst: a new understanding of the binary accretion disk and the secondary star
• Novae Ejecta as Discrete Adiabatically Expanding Globules
• U Sco 2010 outburst: observational evidence of an underlying ONeMg white dwarf
• X-ray Eclipse Diagnosis of the Evolving Mass Loss in the Recurrent Nova U Scorpii 2010