ar X iv : a st ro - p h / 01 07 22 8 v 1 1 3 Ju l 2 00 1 Compact Objects and Accretion Disks By ROGER BLANDFORD

Recent developments in the spectropolarimetric study of compact objects, specifically black holes (stellar and massive) and neutron stars are reviewed. The lectures are organized around five topics: disks, jets, outflows, neutron stars and black holes. They emphasize physical mechanisms and are intended to bridge the gap between the fundamentals of polarimetry and the phenomenology of observed cosmic sources of polarized radiation, as covered by the other lecturers. There has been considerable recent progress in spectropolarimetry from radio through optical frequencies and this is producing some unique diagnostics of the physical conditions around compact objects. It is argued that there is a great need to develop a correspondingly sensitive polarimetric capability at ultraviolet through γ-ray energies. Spectropolarimetric observations, particularly those at radio and optical wavelengths, have played an important role in high energy astrophysics. From the discovery of synchrotron radiation to the first good evidence for AGN unification, from the polarization patterns in the coherent emission of radio pulsars to the discovery of variable, linear polarization in the absorption troughs of broad absorption line quasars, polarization studies often provide the best and sometimes the only clue we have as to the geometric disposition of the emitting elements in these diverse sources when we cannot resolve them directly. These notes summarize lectures delivered by Roger Blandford at the XII Canary Islands Winter School on Astrophysical Spectropolarimetry. They are written up with the assistance of Eric Agol (Disks), Leon Koopmans (Jets), Hee-Won Lee (Outflows), Jeremy Heyl (Neutron Stars) and Avery Broderick (Black Holes) The lectures were intended to provide a bridge between the general physical foundations of polarimetry and its practical description presented at the school by Drs. Landi Degl'Innocenti and Keller and the observationally oriented lectures of Drs. Antonucci and Hildebrand. They also make some important connections to solar, stellar (especially white dwarf) and maser polarimetry as described by Drs. Stenflo, Mathys and Elitzur, respectively. They are organised around five generic astrophysical sources: disks, jets, winds, neutron stars, and black holes. In each case a cursory motivation is provided by summarizing some relevant observations and presenting some of the key issues that polarimetry can help to resolve. This is followed by an heuristic discussion of some relevant physical mechanisms in a manner which, it is hoped, will allow them to be applied elsewhere followed by a brief account of how they have been used so far and some suggestions of possible future …