SiO maser astrometry of the red transient V838 Monocerotis^⋆

¹ Max Planck Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
e-mail: gortiz@mpifr-bonn.mpg.de
² Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
³ Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Rabiańska 8, 87-100 Toruń, Poland

Received: 11 February 2020
Accepted: 3 April 2020

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.