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M. P. Muno, R. A. Remillard, D. Chakrabarty (MIT )
We have examined the complete public database of RXTE PCA observations of several neutron-star low-mass X-ray binaries, which now spans over 5 years. For the first time, we show the complete range of spectral variability observed from the ``atoll'' sources, which was previously unknown because (1) few atoll sources vary over a wide enough range of luminosity, and (2) earlier instruments did not observe these sources frequently enough on time scales longer than weeks. The patterns which atoll sources trace in X-ray color-color diagrams are tantalizingly similar to the shapes for which the more-luminous ``Z'' sources are named. We briefly discuss the observations that are needed to explore the similarities between these two classes of sources in more depth.
The author(s) of this abstract have provided an email address for comments about the abstract: muno@mit.edu