On two occasions , we obtained nearly simultaneous \simeq 4 kilosecond snapshot observations of the Galactic black hole and microquasar XTE J1550 - 564 with Chandra and RXTE near the peak of its May , 2000 outburst .
The low-energy sensitivity of Chandra and the resolution of the High Energy Transmission Grating Spectrometer ( HETGS ) , coupled with the broad energy range and large collecting area of RXTE , have allowed us to place constraints on the outburst accretion flow geometry of this source in the “ intermediate ” X-ray state .
The 0.65–25.0 keV continuum spectra are well-described by relatively hot ( kT \simeq 0.8 keV ) accretion disk and hard ( \Gamma \simeq 2.3 ) coronal power-law components .
Broad , relatively strong Fe K \alpha emission line ( W _ { K \alpha } \simeq 170 eV ) and smeared absorption edge components consistent with Fe XXV are strongly required in joint spectral fits .
The resolution of the Chandra /HETGS reveals that the broad Fe K \alpha emission lines seen clearly in the individual RXTE spectra are not due to an intrinsically narrow line .