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Session 111 - Pulsars.
Display session, Saturday, January 10
Exhibit Hall,

[111.03] RXTE Measurement of Spectral and Temporal Evolution in X-ray Emission from the Galactic Microquasar GRS 1915+105

C. Markwardt (NRC/GSFC), J. Swank (NASA/GSFC), X. Chen (Lick Obs., UC Santa Cruz), R. Taam (Northwestern U.)

The source GRS 1915+105 is one of two recently-discovered galactic sources which have been shown to produce superluminal outflows observable in radio. It has been observed extensively in X-rays by RXTE, and can be extremely variable, with flux changing by factors of 2--3 on timescales as short as several seconds.

We have determined the short-timescale evolution of the photon energy spectrum and power spectral density in 2--8 second increments. The energy spectrum is fit satisfactorily by a power law plus a ``disk'' black body model. The spectral parameters also show dramatic and sudden variations in time, and we present a possible physical interpretation in the context of an unstable accretion disk and corona. The spectral and temporal evidence suggests that the complicated variability that is observed may be comprised of sequences of as few as three distinct phenomenological states.

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