Linear and circular polarimetry observations of GRB afterglows
  Follow-up observations of large numbers of gamma-ray burst (GRB) afterglows,
facilitated by the Swift satellite, have produced a large sample of spectral
energy distributions and light curves, from which the basic micro- and
macrophysical parameters of afterglows may be derived. However, a number of
phenomena have been observed that defy explanation by simple versions of the
standard fireball model, leading to a variety of new models. Polarimetry has
shown great promise as a diagnosis of afterglow physics, probing the magnetic
field properties of the afterglow and geometrical effects (e.g. jet breaks).
Unfortunately, high quality polarimetry of a significant sample of afterglows
is difficult to acquire, requiring specialised instrumentation and observing
modes. In this paper I will review the recent successes in late-time afterglow
polarimetry, also showing first results of new instruments and observing
campaigns. I will particularly focus on jet breaks.
