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Paper: The Photosphere and Stellar Wind of Deneb (A2 Ia) in the Far Ultraviolet
Volume: 348, Astrophysics in the Far Ultraviolet: Five Years of Discovery with FUSE
Page: 124
Authors: Aufdenberg, J.P.; Morrison, N.D.; Hauschildt, P.H.; Adelman, S.J.
Abstract: The A2 Ia-type supergiant star Deneb has been observed by FUSE. A rich absorption spectrum, dominated by Fe II lines, is revealed between 1085Å and 1185Å. The identified lines show no or only small (−25 km s−1) blueward Doppler shifts and no P-Cygni profiles are visible. Apparent emission lines in the spectrum are identified as windows of low opacity and can be reproduced by a PHOENIX hydrostatic model atmosphere. Expanding model atmospheres are needed to reproduce Deneb's excess radio emission and P-Cygni profiles (Hα, Mg II h&k), but, the wind appears largely transparent in the FUSE region. Expanding model atmospheres indicate that enhanced non-LTE ionization of Fe II→Fe III can largely hide the wind in the UV and the FUV. Deneb's Wien tail presents a strong challenge to expanding model atmospheres and promises to provide strong constraints on wind's temperature and ionization structure.
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