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R. M. Wagner (LBT Obs.), S. G. Starrfield (Arizona State U.), P. H. Hauschildt (U. Hamburg)
Optical spectroscopy of V838 Mon was obtained on 2002 Feb. 8 (range 415-675 nm, resolution 0.14 nm) and on Sep. 25 (range 390-750 nm, resolution 0.38 nm) with the 6.5-m MMT of the University of Arizona and the Smithsonian Institution. The Feb. spectrum exhibits strong emission lines of the Balmer series, Fe II, Ba II, Na I D, and weaker features with sharp P Cygni profiles. The width of the emission lines implies an average expansion velocity of about 150 km/s and a terminal velocity of about 350 km/s for a wind or expanding envelope. The spectrum indicates that the progenitor must be a highly evolved object. Preliminary modeling of this spectrum and a HST/STIS UV spectrum obtained a day earlier suggests that the object is deficient in hydrogen and similar in composition to the born-again post-AGB star V4334 Sgr. The Sep. 25th spectrum is composite. Strong TiO and VO bands are seen in the red suggesting a late-M-giant component. At shorter wavelengths, there are strong and narrow absorption lines of the Balmer series and He I (447.1, 587.5 nm). Narrow emission lines arising from [O I] (630.0, 636.3 nm), Mg I (457.1, 516.7 nm), and many other weaker emission and absorption lines are also present. Strong interstellar absorption features of Na I D, 578.0 nm, and perhaps 443.0 nm are present and the equivalent width of 578.0 nm implies E(B-V) = 0.54 mag. The composite spectrum suggests that V838 Mon might be a binary system. These spectra and comparisons with post-AGB stars and eruptive variables such as M31RV and V4332 Sgr will be presented.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.