Electronic Telegram No. 432
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
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RS OPHIUCHI
     T. J. O'Brien, T. W. B. Muxlow, S. T. Garrington, and R. J.
Davis, Jodrell Bank Observatory, University of Manchester; R. W.
Porcas, Max-Planck-Institut fuer Radioastronomie, Bonn; M. F. Bode,
Liverpool John Moores University; S. P. S. Eyres, University of
Central Lancashire; and A. Evans, Keele University, write that 6-cm
radio observations made with the Very Long Baseline Array on Feb. 26
show radio emission from RS Oph in the form of a ring of diameter
approximately 18 mas, consistent with the size of the single circular
component fitted to the MERLIN imaging reported on IAUC 8684.  The
ring appears almost circular, clumpy, significantly brighter on its
eastern side, and with some evidence for a central point source.  At
a distance of 1600 pc, the diameter of the ring is 29 AU and, assuming
that it has expanded uniformly since outburst, its expansion velocity
is about 1800 km/s.  O'Brien et al. suggest that this ring of radio
emission may be identified with a shock wave expanding through the
red-giant wind following the nova explosion, also resulting in the
x-ray emission reported on IAUCs 8675, 8677, and 8683.  VLBA
observations are continuing.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2006 CBAT
2006 March 15                    (CBET 432)               Daniel W. E. Green