Search

We report observations of the nova RS Ophiuchi using the Keck Interferometer Nuller (KIN) taken approximately 3.8 days following the most recent outburst that occurred on 2006 February 12. The KIN operates in N-band from 8 to 12.5 μm in a nulling mode. In this mode the stellar light is suppressed by a destructive fringe, effectively enhancing the contrast of the circumstellar material located near the star. In a second, constructive-fringe mode, the instrument detects primarily the light from the central, bright source. These are the outer and inner spatial regimes, respectively. We will describe the capabilities of the KIN, including these unique modes, and outline how they were key in our discovery that dust was created between nova events. We also show how these first results from the KIN are consistent with Spitzer data. The KIN data show evidence of enhanced neutral atomic hydrogen emission and atomic metals including silicon located in the inner spatial regime (< 4 AU from theWD) relative to the outer regime. There are also nebular emission lines and evidence of hot silicate dust in the outer spatial region, centered at approximately ~ 17 AU from the WD, that are not found in the inner regime. The KIN and Spitzer data suggest that these emissions were excited in the outer spatial regime before the blast wave reached these regions. We describe the present results in terms of a new model for dust creation in recurrent novae 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. These data show the power and potential of the nulling technique which has been developed for the detection of Earth-like planets around nearby stars for the Terrestrial Planet Finder Mission and Darwin missions.

We simulate the actions of a coronagraph matched to diffraction-limited adaptive optics (AO) systems on the Calypso 1.2 m, Palomar Hale 5 m and Gemini 8.1 m telescopes, and identify useful parameter ranges for AO coronagraphy on these systems. We model the action of adaptive wavefront correction with a tapered, high-pass filter in spatial frequency rather than a hard low frequency cutoff, and estimate the minimum number of AO channels required to produce sufficient image quality for coronagraphic suppression within a few diffraction widths of a central bright object (as is relevant to e.g., brown dwarf searches near late-type dwarf stars). We explore the effect of varying the occulting image- plane stop size and shape, and examine the trade-off between throughput and suppression of the image halo and Airy rings. We discuss our simulations in the context of results from the 241-channel Palomar Hale AO coronagraph system, and suggest approaches for future AO coronagraphic instruments on large telescopes.