On the distance, reddening and progenitor of V838 Mon

Abstract

Abstract. Extensive optical and infrared photometry as well as low and high resolution spectroscopy are used as inputs in deriving robust estimates of the reddening, distance and nature of the progenitor of V838 Mon, the 2002 outbursting event that produced a most spectacular light-echo. The reddening affecting V838 Mon is found to obey the R V = 3.1 law and amounts to (i) E B−V = 0.86 from the interstellar NaI and KI lines; (ii) E B−V = 0.88 from the energy distribution of the B3 V component; and (iii) E B−V = 0.87 from the progression of extinction along the line of sight. The adopted E B−V = 0.87 ± 0.01 is also the amount required by fitting the progenitor with theoretical isochrones of appropriate metallicity. The distance is estimated from (a) the galactic kinematics of the three components of the interstellar lines; (b) the amount of extinction vs. the HI column density and vs. the dust emission through the whole Galaxy in that direction; from (c) spectrophotometric parallax to the B3 V companion; from (d) comparison of the observed color−magnitude diagram of field stars with 3D stellar population models of the Galaxy; from (e) comparison of theoretical isochrones with the components of the binary system in quiescence and found to be around 10 kpc. Pre-outburst optical and IR energy distributions show that the component erupting in 2002 was brighter and hotter than the B3 V companion. The best fit is obtained for a 50 000 K source, 0.5 mag brighter than the B3 V companion. The latter passed unaffected through the outburst, which implies an orbital separation wide enough to avoid mass exchange during the evolution of the binary system, and to allow a safe comparison with theoretical isochrones for single stars. Such a comparison suggests that the progenitor of the outbursting component had an initial mass ∼65 M , that it was approaching the carbon ignition stage in its core at the time it erupted in 2002 and that the age of the V838 Mon binary system is close to 4 million yr. The 2002 event is probably just a shell thermonuclear event in the outer envelope of the star.

Eclipse of the B3V companion and flaring of emission lines in V838 Monocerotis

“…Adopting 7 M for the main sequence B3V companion, the orbital period corresponding to the 28 AU lower limit to the orbital separation is 40 yr for an LtSG mass of 7 M , and 20 yr for 40 M 1 . The possibility of a heavy LtSG (progenitor) has been discussed by Munari et al (2005) and Hirschi (2007). The eclipse lasted for ≤1/150 of the orbital period, and in spite of the huge difference in radius of the two stars (B3V and LtSG) it did not go through a flat bottom.…”

“…Viotti et al 1999), far beyond the scope of this paper, and it will be discussed elsewhere together with modeling of the Hα profile evolution. However, it is intriguing to note that the velocity of the absorption component ( RV abs = +4.8 km s Table 3 are arranged in multiplets and their intensity -this time corrected for E B−V = 0.87 reddening (Munari et al 2005) -is given relative to the strongest line of each multiplet. The wavelengths are corresponding laboratory ones.…”

“…Lawlor (2005Lawlor ( , 2007 discussed a model for the outburst of V838 Mon based on a born-again plus accretion scenario on a 1 M star in a binary system. Munari et al (2005) suggested for V838 Mon a helium flash on a once more massive progenitor, evolved by heavy mass-loss into the region of Wolf-Rayet stars at the time of observed eruption. Goranskij et al (2007) similarly argued in favor of a hot and massive progenitor binary system for V4332 Sgr.…”

V1309 Scorpii: merger of a contact binary

“…Several interpretations of the eruptions were proposed. They include an unusual classical nova (Iben & Tutukov 1992;Shara et al 2010), a late He-shell flash (Lawlor 2005), or a thermonuclear shell flash in an evolved massive star (Munari et al 2005). presented numerous arguments against these mechanisms.…”

Light echo of V838 Monocerotis: properties of the echoing medium

“…Munari et al (2005) derived V = 16.05 ± 0.05 for the companion of V838 Mon. Using the compilation of photometric data of V. Goranskij 1 , one derives V = 16.19 ± 0.03 from the data obtained in SeptemberNovember 2002.…”