Keith Horne
St.Andrews
Astrotomography exploits occultations, doppler shifts, rotation, and time delays to map stellar and planetary surfaces, and gas flows in binary star systems and active galactic nuclei. Micro-arcsecond resolution is typically achieved. In cataclysmic variables, where eclipses by a cool companion star dissect the surface of an accretion disk orbiting a white dwarf, we use eclipse mapping to reconstruct monochromatic images of the disk and spectra from any desired region of its surface. With Doppler tomography we map emission-line regions by using changes in the velocity profile as the binary star rotates. This reveals the radial and azimuthal structure of accretion disk chromospheres, the ballistic trajectory of the gas stream, the stream-disk collision region, the irradiated face of the companion star, magnetically-controlled accretion curtains and slingshot prominences. With echo mapping we exploit time delays between hard radiation generated near the compact object at the focus of the flow, and softer emission generated by irradiation of regions farther out. This technique is used to resolve radial ionization structure and kinematics of photo-ionized emission-line regions 1-100 light days from the nuclei of Seyfert galaxies, and is currently being extended to mapping 0.1-10 light-second structure of reprocessing sites in X-ray binaries using simultaneous X-ray and optical light curves.