An analysis of a spectrum of V838 Monocerotis in October 2005

摘要

V838 Mon erupted at the beginning of 2002. Among various scenarios proposedto explain the nature of the outburst, the most promising is a stellar mergerevent. The results of spectroscopic observations of the object obtained inOctober 2005 with the Keck/HIRES instrument, presented in detail in Paper I,are analysed and discussed. Our analysis of the molecular bands and the P-Cygprofiles of atomic lines shows that the object loses matter with a velocity ofup to 215 km/s and a rate of 10^{-6} - 10^{-5} M_sun/yr. In the profiles ofsome atomic lines, we have also found evidence of matter infall. A narrowabsorption component, which is particularly strong in some P-Cyg profiles, mayindicate that a jet-like outflow has also been formed. We show that theobserved emission in the [Fe II] lines and an eclipse-like event observed inNovember/December 2006 was probably caused by interactions of the expandingmatter, ejected by V838 Mon in 2002, with radiation from the B3V companion. Inparticular, the observed profiles of the [Fe II] lines can be easily modelledin this scenario and allow us to estimate parameters of the system, such as theposition of the B3V companion relative to V838 Mon and the line of sight,density in the outflowing matter, and mass lost in the 2002 eruption. Theobserved appearance of strong H-alpha emission, just before and during theeclipse-like event, can be interpreted as a result of the accretion of theoutflowing matter onto the B3V companion: the accreted matter, shocked abovethe stellar surface, can be a source of extreme-UV and soft X-ray radiationcapable of ionizing and exciting H in the outflow.