Munari, U.; Corradi, R. L. M.; Henden, A.; Navasardyan, H.; Valentini, M.; Greimel, R.; Leisy, P.; Augusteijn, T.; Djupvik, A. A.; Glowienka, L.; Somero, A.; de La Rosa, I. G.; Vazdekis, A.; Kolka, I.; Liimets, T.
Astronomy and Astrophysics, Volume 474, Issue 2, November I 2007, pp.585-590
After four years during which only the spectacular light echo was showing continuous and rapid evolution while the central star was nearly constant, in autumn 2006 V838 Mon began a sequence of events which profoundly altered its spectroscopic and photometric behavior: (a) an eclipse of the B3V companion, characterized by the disappearance and reappearance of the B3V companion from optical spectra, and an eclipse-like lightcurve of ~70 day duration and Δ B ˜ 1.15 mag, Δ V ˜ 0.55 mag, Δ RC ˜ 0.10 mag maximum depth; (b) a large increase in intensity of the [FeII] and FeII emission lines, and the appearance in emission for the first time since the 2002 outburst of Hα and higher Balmer series lines. While the [FeII] and FeII lines maintained a very sharp and unresolved profile, the Hα developed into a wide and structured profile, characterized by a sharp central reversal at the same velocity as one of the CO radio emission components. The disappearance of the B3V companion is equally well explained by a grazing eclipse from the outbursting L-type supergiant or by an eclipse from a dust cloud characterized by EB-V=0.55 and RV=3.1. We believe the flaring of the emission lines occurred at a similar time as the B3V eclipse just by chance.
Tables 2-4 are only available in electronic form at http://www.aanda.org Based on observations made with the Asiago 1.82 m of the INAF Astronomical Observatory of Padova, and with 4.2 m WHT and 2.5 m INT operated by the Isaac Newton Group of Telescopes, and with the 2.6 m NOT operated jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de Los Muchachos of the Instituto de Astrofísica de Canarias.