AAS 201st Meeting, January, 2003
Session 40. Normal and Dwarf Novae
Poster, Tuesday, January 7, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[40.02] Optical Spectroscopy of V838 Monocerotis

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.