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Session 7 - Planetary & Other Nebulae.
Display session, Monday, June 09
South Main Hall,
We present recent NRAO VLA and VLBA observations of the R Aqr binary system obtained during two observing sessions. In November, 1996 we used the VLA in the A configuration at \lambda7mm. In December, 1995 we observed R Aqr at \lambda6cm using the VLBA in combination with the B configuration VLA. We also reprocessed archival VLA data taken at \lambda6cm in the B configuration in September, 1982.
The \lambda 7mm observations have for the first time resolved the stellar components of the R Aqr binary system (Hollis, Pedelty, and Lyon 1997, ApJ Letters, in press). We measure an apparent projected separation between the Long Period Variable (LPV) and its hot companion of 55 \pm 2 milli-arcseconds with a position angle of \sim 18^\circ \pm 2^\circ relative to the LPV. We derive an orbital geometry using this initial image along with some reasonable assumptions and obtain a geometrical distance of \sim 200 pc to R Aqr. We also obtained a spectral line image which confirms the ring-like morphology of the LPV SiO maser spots.
However, we find that the R Aqr \lambda6cm radio emission is over-resolved by the combined VLBA/VLA. We obtain an upper limit for the \sim milli-arcsecond scale flux density of 0.4 mJy (5 \sigma).
Our two sets of VLA B configuration observations at \lambda6cm are separated by 13.2 years. Comparison of the \sim 1" resolution images shows that the R Aqr jet has undergone an apparent counter- clockwise rotation of \sim 6 - 12^\circ on the plane of the sky. These observations, along with previously published proper motion studies, are difficult to reconcile with a garden hose model for the R Aqr jet.
Program listing for Monday