  The first detection of gravitational waves by LIGO from the merger of two
compact objects has sparked new interest in detecting electromagnetic
counterparts to these violent events. For mergers involving neutron stars, it
is thought that prompt high-energy emission in gamma rays and x-rays will be
followed days to weeks later by an afterglow in visible light, infrared and
radio. Rapid sky localization using the data from a network of gravitational
wave detectors is essential to maximize the chances of making a joint
detection. Here I describe a new technique that is able to produce accurate,
fully Bayesian sky maps in seconds or less. The technique can be applied to
spin-precessing compact binaries, and can take into account detector
calibration and spectral estimation uncertainties.
