SiO maser astrometry of the red transient V838 Monocerotis

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 0.166ℓ ±ℓ 0.060 mas. Combining this parallax with other distance information results in a distance of 5.6ℓ ±ℓ 0.5 kpc, which is in agreement with an independent geometric distance of 6.1ℓ ±ℓ 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 5.9ℓ ±ℓ 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.