AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 50. High Angular Resolution Science with the NRAO Very Long Baseline Array
Display, Tuesday, June 1, 1999, 10:00am-7:00pm, Southwest Exhibit Hall

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[50.07] Extremely Rapid Structure Variations in Sco X-1

B.J. Geldzahler (George Mason University), E.B Fomalont (National Radio Astronomy Obs.), C.F. Bradshaw (George Mason U.)

VLBA observations with 2 mas resolution of Sco X-1 on Aug 21/22, 1997, when the source was in a flaring state, indicate that most of the flux density variations are occurring along a well-defined position angle in small clouds ( 106 km), but typically 109 km from the binary system. The flux density variations coincide with variations in the structure of Sco X-1 which we find to occur on a time scale of 80 seconds. This time scale is set by the sensitivity limits of the VLBA and could well be an upper limit.

The radiative lifetime of these clouds is typically a, few minutes of time. We believe that the clouds, are heated by interaction with a narrow dual-beam of energetic particles or photons from the accretion disk. The rapid cooling may be associated with inverse-Compton radiation of small clouds. We believe the clouds are associated with moving shells of material which have been ejected from Sco X-1. The asymmetry of the radio emission in the NE to SW direction are consistent with the shells moving with velocity 0.3c, about 60' from the line of sight, as suggested by the splitting of the kHz QPO x-ray emission.

We discuss using Sco X-1 as a microcosmic laboratory of the more powerful active galactic nuclei and quasars and the implications of the rapid flux density and structure variations in the context of intraday variability observed in extragalactic radio sources.

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