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Register a new userThe Planets-Capture Model of V838 Monocerotis
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Authors
Alon Retter
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The planets capture model for the eruption of V838 Mon is discussed. We used three methods to estimate the location where the planets were consumed. There is a nice consistency for the results of the three different methods, and we find that the typical stopping / slowing radius for the planets is about 1Ro. The three peaks in the optical light curve of V838 Mon are either explained by the swallowing of three planets at different radii or by three steps in the slowing down process of a single planet. We discuss the other models offered for the outburst of V838 Mon, and conclude that the binary merger model and the planet/s scenario seem to be the most promising. These two models have several similarities, and the main differences are the stellar evolutionary stage, and the mass of the accreted material. We show that the energy emitted in the V838 Mon event is consistent with the planets scenario. We suggest a few explanations for the trigger for the outburst and for the double structure of the optical peaks in the light curve of V838 Mon.
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We have used long-baseline near-IR interferometry to resolve the peculiar eruptive variable V838 Mon and to provide the first direct measurement of its angular size. Assuming a uniform disk model for the emission we derive an apparent angular diameter at the time of observations (November-December 2004) of $1.83 pm 0.06$ milli-arcseconds. For a nominal distance of $8pm2$ kpc, this implies a linear radius of $1570 pm 400 R_{odot}$. However, the data are somewhat better fit by elliptical disk or binary component models, and we suggest that the emission may be strongly affected by ejecta from the outburst.
Luminous Red Variables (LRVs) are most likely eruptions that are the outcome of stellar mergers. V838 Mon is one of the best-studied members of this class, representing an archetype for stellar mergers resulting from B-type stars. As result of the merger event, nova-like eruptions occur driving mass-loss from the system. As the gas cools considerable circumstellar dust is formed. V838 Mon erupted in 2002 and is undergoing very dynamic changes in its dust composition, geometry, and infrared luminosity providing a real-time laboratory to validate mineralogical condensation sequences in stellar mergers and evolutionary scenarios. We discuss recent NASA Stratospheric Observatory for Infrared Astronomy SOFIA 5 to 38 micron observations combined with archival NASA Spitzer spectra that document the temporal evolution of the freshly formed (within the last 20 yrs) circumstellar material in the environs of V838 Mon. Changes in the 10 micron spectral region are strong evidence that we are witnessing a classical dust condensation sequence expected to occur in oxygen-rich environments where alumina formation is followed by that of silicates at the temperature cools.
We report the discovery of multiple shells around the eruptive variable star V838 Mon. Two dust shells are seen in IRAS and MSX images, which themselves are situated in a shell of CO. This securely establishes V838 Mon as an evolved object. We revisit the light echo, which arises from scattering off the innermost resolved dust shell, to infer a distance to V838 Mon of >~5.5 kpc. The dynamical timescales of the ejected shells, location in the Milky Way and inferred luminosity are consistent with V838 Mon being a low-mass AGB star experiencing thermal pulses of which the 2002 eruption might have sent the star into the post-AGB phase. This scenario, however, is inconsistent with the presence of a (young and massive) B3 V companion.
We present multi-epoch observations with the VLBA of SiO maser emission in the v=1, J=1-0 transition at 43 GHz from the remnant of the red nova V838 Mon. We model the positions of maser spots to derive a parallax of 0.166+/-0.060 mas. Combining this parallax with other distance information results in a distance of 5.6+/-0.5 kpc, which agrees with an independent geometric distance of 6.1+/-0.6 kpc from modeling polarimetry images of V838 Mons light echo. Combining these results, and including a weakly constraining Gaia DR2 parallax, yields a best estimate of distance of 5.9+/-0.4 kpc. The maser spots are located close to the peaks of continuum at ~225 GHz and SiO J=5-4 thermal emission detected with ALMA. The proper motion of V838 Mon confirms its membership in a small open cluster in the Outer spiral arm of the Milky Way.
We report high spatial resolution 11.2 and 18.1 micron imaging of the eruptive variable V838 Monocerotis, obtained with Gemini Observatorys Michelle in 2007 March. The 2007 flux density of the unresolved stellar core is roughly 2 times brighter than that observed in 2004. We interpret these data as evidence that V838 Mon has experienced a new circumstellar dust creation event. We also report a gap of spatially extended thermal emission over radial distances of 1860-93000 AU from the central source, which suggests that no prior significant circumstellar dust production events have occurred within the past 900-1500 years.
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