MilliarcsecondN‐Band Observations of the Nova RS Ophiuchi: First Science with the Keck Interferometer Nuller

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 m 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.

Nova Eruptions with Infrared Interferometric Observations

“…A two velocity component was also required to replicate the Hubble Space Telescope narrow band imaging observations of the resolved remnant, at day 155 after eruption, and the ground-based optical spectroscopy (Ribeiro et al 2009). Lastly, RS Oph observations with the Keck Interferometer Nuller, around day 3.8 after eruption, showed evidence for dust that is present in-between eruptions, rather than created during the eruption (Barry et al 2008) in line with findings from the Spitzer Space Telescope of silicate dust that survives the hard radiation impulse and shock blast wave from the eruption (Evans et al 2007). …”

The PRIMA fringe sensor unit

“…Because it is the equivalent of adaptive optics for singledish telescopes, fringe tracking partly removes the atmospheric piston turbulence that limits the quality of interferometric measurements, at the cost of decreased sensitivity. After the first demonstration by Shao & Staelin (1980), fringe tracking has become a common feature of modern optical interferometers and opened the path to new scientific results (Monnier 2003;Barry et al 2008;Le Bouquin et al 2009b). It makes narrow-angle astrometry of the order of 100 μas possible, which is demonstrated both in single-beam interferometry (Colavita 1994;Lane & Muterspaugh 2004a) and later in a dual-beam interferometer, where the technique is extended to off-axis fringe tracking and phase referencing (Lane & Colavita 2003).…”

The LBTI hunt for observable signatures of terrestrial systems (HOSTS) survey: a key NASA science program on the road to exoplanet imaging missions

“…The leakage is the difference between the null signal from a target star minus the null signal from a reference star. The leakage can also be related to traditional interferometric quantities such as the visibility, where the null quantity, N, is given by N = (1− V ) / (1+ V ) , where V is the magnitude of the complex visibility as it is usually defined, e.g., the Fourier transform of the brightness distribution of the source (see papers by Barry et al [17], Serabyn et al [18] for more detailed discussions).…”