  Excellent coverage of the 1998 outburst of the X-ray Nova XTE J1550-564 was
provided by the Rossi X-ray Timing Explorer. XTE J1550-564 exhibited an intense
(6.8 Crab) flare on 1998 September 19 (UT), making it the brightest new X-ray
source observed with RXTE. We present a spectral analysis utilizing 60
Proportional Counter Array spectra from 2.5-20 keV spanning 71 days, and a
nearly continuous All Sky Monitor light curve. The spectra were fit to a model
including multicolor blackbody disk and power-law components. XTE J1550-564 is
observed in the very high, high/soft, and intermediate canonical outburst
states of Black Hole X-ray Novae.
