Distance to VY Canis Majoris with VERA

TL;DR

This paper presents the most accurate distance measurement to VY Canis Majoris using VLBI astrometry, leading to revised luminosity estimates and improved understanding of its position on the HR diagram.

Contribution

First precise parallax measurement of VY CMa using VERA, significantly refining its distance and luminosity estimates.

Findings

Measured a parallax of 0.88 +/- 0.08 mas for VY CMa.

Revised the star's luminosity to approximately 3 x 10^5 L_sun.

Located VY CMa closer to the theoretical stellar evolution zone.

Abstract

We report astrometric observations of H2O masers around the red supergiant VY Canis Majoris (VY CMa) carried out with VLBI Exploration of Radio Astrometry (VERA). Based on astrometric monitoring for 13 months, we successfully measured a trigonometric parallax of 0.88 +/- 0.08 mas, corresponding to a distance of 1.14 +0.11/-0.09 kpc. This is the most accurate distance to VY CMa and the first one based on an annual parallax measurement. The luminosity of VY CMa has been overestimated due to a previously accepted distance. With our result, we re-estimate the luminosity of VY CMa to be (3 +/- 0.5) x 10^5 L_sun using the bolometric flux integrated over optical and IR wavelengths. This improved luminosity value makes location of VY CMa on the Hertzsprung-Russel (HR) diagram much closer to the theoretically allowable zone (i.e. the left side of the Hayashi track) than previous ones, though uncertainty in the effective temperature of the stellar surface still does not permit us to make a final conclusion.