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Session 52 - HEAD I: First Results from RXTE.
Oral session, Tuesday, January 14
Frontenac Ballroom,

[52.01] Accretion Disk Instabilities in Galactic Microquasars

E. Morgan (MIT)

There are two Galactic X-ray sources which exhibit superluminal radio jets, GRS 1915+10 and GRO J1655-40. Both of these micro-quasars have been extremely active in 1996. Long term light curves from the RXTE All Sky Monitor show dramatic intensity variations between 1 and 4 Crab. Followup observations of GRS 1915+10 with the pointing instruments on RXTE reveal a rich phenomenology of QPO at frequencies ranging from 1 mHz to 67 Hz. The QPO phase, wave forms and spectral signatures of many of these QPO can be tracked. There is a QPO phase lag and the QPO amplitude changes as a function of photon energy. The deviation of the QPO phase from strict periodicity is well described by a random walk. The combined characteristics of the power spectra, light curves, and energy spectra delineate a distinct succession of different emission states, none of which appears identical to any of the canonical states of black hole binaries. RXTE observations another Galactic source with radio jets, Cir X-1, also show strong QPO and dramatic time variability, that depend on the orbital phase. The observations may lead to a better understanding of the instabilities in the inner accretion disk and the formation of jets.

Program listing for Tuesday