PCA observations of Cyg X-1 from RXTE using fast timing and high telemetry rates

Abstract

The Rossi X-ray Timing Explorer (RXTE) spacecraft contains a very large area, high resolution timing experiment provided by the NASA's Goddard Space Flight Center. This Proportional Counter Array (PCA) has an area of 7000 cm 2 and a time resolution down to one micro second. A 450 Mbit memory on board the spacecraft allows science data acquisition at rates up to 512 kbps but a more typical high rate of ∼256 kbps can be continuously supported for up to 30 minutes. This performance far surpasses previous rocket and satellite timing experiments. Since the launch of RXTE several observations have been made of Cyg X-1 in this special high telemetry rate mode to specifically search for, and attempt to confirm, the existence of millisecond bursts. Such features were reported in several observations of Cyg X-1 in the mid 1970's. This paper briefly summarizes the PCA performance compared to earlier large timing experiments and then presents early results from the analysis of these data sets. Individual millisecond bursts do not seem to exist in the data examined so far.