Milliarcsecond N-Band Observations of the Nova RS Ophiuchi: First Science with the Keck Interferometer Nuller

Creators: Barry, R. K.; Danchi, W. C.; Traub, W. A.; Sokoloski, J. L.; Wisniewski, J. P.; Serabyn, E.; Kuchner, M. J.; Akeson, R.; Appleby, E.; Bell, J.; Booth, A.; Brandenburg, H.; Colavita, M.; Crawford, S.; Creech-Eakman, M.; Dahl, W.; Felizardo, C.; Garcia, J.; Gathright, J.; Greenhouse, M. A.; Herstein, J.; Hovland, E.; Hrynevych, M.; Koresko, C.; Ligon, R.; Mennesson, B.; Millan-Gabet, R.; Morrison, D.; Palmer, D.; Panteleeva, T.; Ragland, S.; Shao, M.; Smythe, R.; Summers, K.; Swain, M.; Tsubota, K.; Tyau, C.; Wetherell, E.; Wizinowich, P.; Woillez, J.; Vasisht, G.

Abstract

We report observations of the nova RS Ophiuchi (RS Oph) using the Keck Interferometer Nuller (KIN), approximately 3.8 days following the most recent outburst that occurred on 2006 February 12. These observations represent the first scientific results from the KIN, which operates in N band from 8 to 12.5 μm in a nulling mode. The nulling technique is the sparse aperture equivalent of the conventional coronagraphic technique used in filled aperture telescopes. In this mode the stellar light itself is suppressed by a destructive fringe, effectively enhancing the contrast of the circumstellar material located near the star. By fitting the unique KIN data, we have obtained an angular size of the mid-infrared continuum emitting material of 6.2, 4.0, or 5.4 mas for a disk profile, Gaussian profile (FWHM), and shell profile, respectively. The data show evidence of enhanced neutral atomic hydrogen emission and atomic metals including silicon located in the inner spatial regime near the white dwarf (WD) relative to the outer regime. There are also nebular emission lines and evidence of hot silicate dust in the outer spatial region, centered at ~17 AU from the WD, that are not found in the inner regime. Our evidence suggests that these features have been excited by the nova flash in the outer spatial regime before the blast wave reached these regions. These identifications support a model in which the dust appears to be present between outbursts and is not created during the outburst event. We further discuss the present results in terms of a unifying model of the system that includes an increase in density in the plane of the orbit of the two stars created by a spiral shock wave caused by the motion of the stars through the cool wind of the red giant star.

Additional Information

© 2008 The American Astronomical Society. Received 2007 August 9; accepted 2008 January 9. We are grateful to the National Aeronautics and Space Administration, Jet Propulsion Laboratory, the California Association for Research in Astronomy, the Harvard-Smithsonian Center for Astrophysics (including SAO grant G06-7022A to J. L. S.), and to the National Aeronautics and Space Administration, Goddard Space Flight Center for support of this research. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. J. P. W. acknowledges support provided by an NPP Fellowship (NNH06CC03B) at NASA Goddard Space Flight Center. This work has made use of services produced by the Michelson Science Center at the California Institute of Technology. One of the authors (R. K. B.) would also like to acknowledge Eugene E. Rudd formerly of the United States Naval Research Laboratory for his continued support and encouragement. The authors thank the referee, Michael Bode, for his careful and thorough review of the manuscript, which has helped us to significantly improve it. Facilities: Spitzer, IOTA, Keck:I, Keck:II.

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