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We characterized the evolution of spectral and temporal properties of several Galactic black hole transients observed between 1996–2001 using the data from well sampled PCA observations close to the transition to the low/hard state. We showed that the changes in temporal properties are much sharper than the changes in the spectral properties, and it is much easier to identify a state transition with the temporal properties. The ratio of the power-law flux to the total flux in the 3–25 keV band increases close to the transition, and the power-law flux shows a sharp increase along with the changes in temporal properties during the transitions. In this work we concentrate on the decay of two recent outbursts, from 4U 1543-47, and H1743-322 and discuss the state transitions by tracking their daily, and sometimes hourly evolution, and interpret results based on the expectations from our earlier observations. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The great success of the Rossi X-Ray Timing Explorer (RXTE) has given us a new probe to study strong gravitational fields and to measure the physical properties of black holes and neutron stars. Here, we describe a "next-generation" x-ray timing mission, the Relativistic Astrophysics Explorer (RAE), designed to fit within the envelope of a "medium-sized" mission. The main instruments will be a narrow-field x-ray detector array with an area of at least 60,000 cm² equal to ten times that of RXTE, and a wide-field x-ray monitor with good sensitivity and few arcminute position resolution. We describe the design of the instruments and the science which will be possible with a factor of ten increase in collecting area. [ABSTRACT FROM AUTHOR]

We report on radio, near-infrared, optical and X-ray observations of the black hole candidate (BHC) XTE J1550-564 performed during its 2000 X-ray outburst. These observations have allowed us to sample the behavior of XTE J1550-564 in the X-ray Low Hard and Intermediate/Very High states. The radio emission in the Low Hard state most likely originates from a compact jet and the synchrotron emission from this jet may extend up to the optical range or beyond, therefore indicating that the total power of the compact jet is a significant fraction of the total luminosity of the system. In the Intermediate/Very High state the radio emission is quenched, implying a suppression of the outflow. We discuss the properties of radio emission in the X-ray states of BHCs. [ABSTRACT FROM AUTHOR]