Scientific Colloquium
January 13, 2006

"The Impact of RossiXTE on General Relativistic and High Energy Astrophysics"
Using RossiXTE, astronomers have discovered that accreting neutron 
stars and black holes produce several types of very high frequency X-ray
oscillations. These oscillations are powered by energy released 
deep in the strong gravitational fields of neutron stars and black 
holes. They are being used to explore fundamental physics, such 
strong-field gravity and the properties of matter under extreme 
conditions, and important astrophysical questions, such as the 
formation and evolution of neutron stars and black holes. Study of 
these oscillations has greatly narrowed the possible descriptions of 
ultradense matter, indicated that some black holes in binary systems 
are rapidly spinning, and revealed that dozens of neutron stars have 
very high spin rates and magnetic fields strong enough to become 
millisecond radio-emitting pulsars when accretion ceases. Analysis of 
the kilohertz oscillations has provided the first evidence for the 
existence of the innermost stable circular orbit around compact 
massive objects predicted by strong-field general relativity.