AAS Meeting #193 - Austin, Texas, January 1999
Session 111. Supernovae and Atmospheric Phenomena in Binaries
Oral, Saturday, January 9, 1999, 10:00-11:30am, Room 6 (A and B)

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[111.05] VLBI Detection of Motion of IM Pegasi Radio Emission on Hour Time Scales Coincident with Changes in Flux Density

D. E. Lebach, M. I. Ratner, I. I. Shapiro (CfA), N. Bartel, M. F. Bietenholz, R. R. Ransom (York U.), J. F. Lestrade (Obs. de Meudon)

VLBI continuum observations at 3.6~cm of the RS Canum Venaticorum binary star IM~Pegasi (HR~8703) on 1997~January 16--17 and 18--19, made in support of the NASA-Stanford Relativity Gyroscope Experiment (Gravity Probe B), revealed ~1~mas motions of its radio centroid over time periods as short as ~1~h. These motions, which we deduced from phase-delay measurements using a Kalman-filter estimator, coincided temporally with changes in the star's flux density measured with the VLA. Phase-referenced maps of the stellar radio emission show motions consistent with those found with the Kalman-filter estimator. We present our estimates of source motion as a function of time during our observations, and discuss the corresponding evolution of the structure seen in our phase-referenced maps. We also discuss what we may learn from additional VLBI observations of the star, which we continue to make at the rate of ~4 per year.

The author(s) of this abstract have provided an email address for comments about the abstract: dlebach@cfa.harvard.edu

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