SIMBAD references

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.