THE EXPANDING NEBULAR REMNANT OF THE RECURRENT NOVA RS OPHIUCHI (2006). II. MODELING OF COMBINED<i>HUBBLE SPACE TELESCOPE</i>IMAGING AND GROUND-BASED SPECTROSCOPY

Abstract

We report Hubble Space Telescope imaging, obtained 155 and 449 days after the\n2006 outburst of the recurrent nova RS Ophiuchi, together with ground-based\nspectroscopic observations, obtained from the Observatorio Astron\\'omico\nNacional en San Pedro M\\'artir, Baja California, M\\'exico and at the\nObservatorio Astrof\\'isico Guillermo Haro, at Cananea, Sonora, M\\'exico. The\nobservations at the first epoch were used as inputs to model the geometry and\nkinematic structure of the evolving RS Oph nebular remnant. We find that the\nmodeled remnant comprises two distinct co-aligned bipolar components; a\nlow-velocity, high-density innermost (hour glass) region and a more extended,\nhigh-velocity (dumbbell) structure. This overall structure is in agreement with\nthat deduced from radio observations and optical interferometry at earlier\nepochs. We find that the asymmetry observed in the west lobe is an instrumental\neffect caused by the profile of the HST filter and hence demonstrate that this\nlobe is approaching the observer. We then conclude that the system has an\ninclination to the line of sight of 39$^{+1}_{-10}$ degrees. This is in\nagreement with the inclination of the binary orbit and lends support to the\nproposal that this morphology is due to the interaction of the outburst ejecta\nwith either an accretion disk around the central white dwarf and/or a\npre-existing red giant wind that is significantly denser in the equatorial\nregions of the binary than at the poles. The second epoch HST observation was\nalso modeled. However, as no spectra were taken at this epoch, it is more\ndifficult to constrain any model. Nevertheless, we demonstrate that between the\ntwo HST epochs the outer dumbbell structure seems to have expanded linearly.\n