An analysis of a spectrum of V838 Monocerotis in October 2005

TL;DR

This study analyzes spectroscopic data of V838 Monocerotis from October 2005, revealing matter loss, infall, and jet-like outflows, and models interactions with its B3V companion to explain observed emission features and an eclipse-like event.

Contribution

It provides detailed spectroscopic analysis and modeling of V838 Mon's outflows, infall, and interactions with its companion, offering new insights into the system's dynamics post-eruption.

Findings

V838 Mon loses matter at up to 215 km/s with a rate of 10^{-6} - 10^{-5} M_sun/yr.

Evidence of matter infall and jet-like outflows was found in spectral profiles.

Interactions with the B3V companion explain observed emission lines and eclipse-like event.

Abstract

V838 Mon erupted at the beginning of 2002. Among various scenarios proposed to explain the nature of the outburst, the most promising is a stellar merger event. The results of spectroscopic observations of the object obtained in October 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-Cyg profiles of atomic lines shows that the object loses matter with a velocity of up to 215 km/s and a rate of 10^{-6} - 10^{-5} M_sun/yr. In the profiles of some atomic lines, we have also found evidence of matter infall. A narrow absorption component, which is particularly strong in some P-Cyg profiles, may indicate that a jet-like outflow has also been formed. We show that the observed emission in the [Fe II] lines and an eclipse-like event observed in November/December 2006 was probably caused by interactions of the expanding matter, ejected by V838 Mon in 2002, with radiation from the B3V companion. In particular, the observed profiles of the [Fe II] lines can be easily modelled in this scenario and allow us to estimate parameters of the system, such as the position 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. The observed appearance of strong H-alpha emission, just before and during the eclipse-like event, can be interpreted as a result of the accretion of the outflowing matter onto the B3V companion: the accreted matter, shocked above the stellar surface, can be a source of extreme-UV and soft X-ray radiation capable of ionizing and exciting H in the outflow.