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C. B. Markwardt, W. B. Focke (NASA's GSFC / U. Maryland), J. H. Swank (NASA's GSFC), R. E. Taam (Northwestern U.)
We present variability studies of a previously unknown X-ray transient, XTE J1859+226. The source was detected by the RXTE All Sky Monitor early on October 9, 1999, reached a relative maximum of approximately 1.5~Crab after 8 days, and began declining irregularly. RXTE PCA pointed observations commenced October 10.56. In a preliminary analysis of the source, a quasiperiodic oscillation was detected near the onset of the outburst, at a centroid frequency of 0.5~Hz, and with at least two harmonics. As the outburst proceeded the frequency of the QPO increased to at least 4~Hz. Further analysis of the power spectra and other timing properties will be presented, as will a comparison to the energy spectral characteristics throughout the evolution of the outburst.