On the light echo in V838 Mon

Abstract

After having presented a theoretical outline of the light echo phenomenon and results of simple numerical simulations we study the available images of the light echo in V838 Mon obtained with HST. From an analysis of the observed expansion of the light echo we conclude that the distance to V838 Mon is greater then $\sim$5 kpc. We also investigate the structure of the dust distribution in the vicinity of the object. We find no obvious signs of spherical symmetry in the resultant distribution. Near the central object there is a strongly asymmetric dust-free region which we interpret as an evidence that V838 Mon is moving relatively to the dusty medium. From these results we conclude that dust illuminated by the light echo is of interstellar origin rather than produced by mass loss from V838 Mon in the past.