Polarimetry of V838 Mon and stars around

The polarization of field stars confirms the previously determined interstellar polarization along the line of sight to V838 Mon. While V838 Mon showed intrinsic polarization shortly after its second outburst on 2002 February 8, all subsequent observations only showed a quiescent interstellar polarization component.

We find that V838 Mon once again showed significant intrinsic polarization in 2002 October, suggesting the presence of an asymmetrical geometry of scattering material close to the star. Furthermore, an observed 90{deg} position angle flip in the intrinsic polarization from 2002 February to October suggests that the distribution of nearby circumstellar material has experienced significant changes. We discuss the opacity changes in the evolving circumstellar cloud around V838 Mon that may explain these observations.