Spectropolarimetry and the study of circumstellar disks

Abstract

Circumstellar disks play an important role in many stages of the evolution of stars. However, it is only possible to directly image circumstellar disks for a few of the nearest stars. For massive stars, the situation is even more difficult, as they are on average further away than the more numerous low mass stars. Here, we discuss spectropolarimetry which is a technique that can reveal the presence of disks on spatial scales of order stellar radii. It is therefore extremely useful in studying disks around young stars, while the method has prospects for quantitative modelling. In this review we will discuss the status on the study of (accretion) disks around intermediate- to high mass pre-main sequence stars and will concentrate on the linear spectropolarimetry aspect. We wil make a brief excursion to observations of massive evolved stars where spectropolarimetry has revealed the clumpy structure of stellar winds, and conclude with a brief outlook.