2002IAUC.7992....2W

R. M. Wagner, LBT Observatory; and S. G. Starrfield, Arizona State University, report: "An optical spectrum (range 390-750 nm; resolution 0.35 nm) of V838 Mon was obtained on Sept. 25.498 UT with the 6.5-m MMT (+ blue channel spectrograph). Our spectrum is composite and thus confirms an earlier report of a weak blue continuum in low-S/N spectra (Desidera and Munari, IAUC 7982). Strong TiO and VO bands are seen in the red, in agreement with the recent spectra, suggesting a late-M-giant component. However, at shorter wavelengths, there are strong and narrow absorption lines of H-beta, H-gamma, H-delta, and He I (447.1, 587.5 nm). The equivalent width of H-beta is 0.6 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. The spectrum exhibits strong interstellar absorption features of Na I D, 578.0 nm, and perhaps 443.0 nm. The equivalent width of 578.0 nm implies E(B-V) = 0.54 mag, corresponding to 1.7 mag of visual extinction and consistent with a previous estimate (Munari et al. 2002, A.Ap. 389, L51) based on outburst spectra. The composite spectrum suggests that this is a binary system consisting of a cool giant and a hot-star companion. Additional blue spectroscopy to ascertain the nature of the hot component is required."