Abstract
We present multiepoch observations with the Very Long Baseline Array 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 modeled 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 is in agreement with an independent geometric distance of 6.1 ± 0.6 kpc from modeling polarimetry images of V838 Mon’s light echo. Combining these results, and including a weakly constraining Gaia 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 the Atacama Large (sub)Millimeter Array. The proper motion of V838 Mon confirms its membership in a small open cluster in the Outer spiral arm of the Milky Way.
Highlights
V838 Mon is a remnant of a so-called red nova, which erupted in January 2002 (Munari et al 2002a) and immediately came to prominence in the astronomical community and the public due to the spectacular images of a light echo taken with the Hubble Space Telescope (HST; Bond et al 2003)
We note that no additional maser components were found, which suggests those may be too weak to be detected with the current sensitivity of our observations
Their individual parallaxes are between 0.17 and 0.24 mas and have a weighted-mean parallax of 0.18 ± 0.10 mas, after correcting for a Gaia DR2 parallax zero-point shift of −0.029 mas1, which agrees with our Very Long Baseline Array (VLBA) parallax of V838 Mon
Summary
V838 Mon is a remnant of a so-called red nova, which erupted in January 2002 (Munari et al 2002a) and immediately came to prominence in the astronomical community and the public due to the spectacular images of a light echo taken with the Hubble Space Telescope (HST; Bond et al 2003) This eruption probably resulted from a merger of two ( 8 M and 0.3 M ) stars (Tylenda & Soker 2006), but other mechanisms have been proposed. Interferometric observations at millimeter/submillimeter wavelengths using the Submillimeter Array (SMA) revealed lines of CO, SiO, SO, SO2, and H2S covering a very broad velocity range (∼400 km s−1; Kaminski et al 2018) These molecular transitions trace thermal emission from the merger ejecta and are orders of magnitude weaker in peak intensity than the SiO maser lines.
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