21 July 2010 First Keck Interferometer measurements in self-phase referencing mode: spatially resolving circum-stellar line emission of 48 Lib
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Abstract
Recently, the Keck interferometer was upgraded to do self-phase-referencing (SPR) assisted K-band spectroscopy at R ~ 2000. This means, combining a spectral resolution of 150 km/s with an angular resolution of 2.7 mas, while maintaining high sensitiviy. This SPR mode operates two fringe trackers in parallel, and explores several infrastructural requirements for off-axis phase-referencing, as currently being implemented as the KI-ASTRA project. The technology of self-phasereferencing opens the way to reach very high spectral resolution in near-infrared interferometry. We present the scientific capabilities of the KI-SPR mode in detail, at the example of observations of the Be-star 48 Lib. Several spectral lines of the cirumstellar disk are resolved. We describe the first detection of Pfund-lines in an interferometric spectrum of a Be star, in addition to Br γ. The differential phase signal can be used to (i) distinguish circum-stellar line emission from the star, (ii) to directly measure line asymmetries tracing an asymetric gas density distribution, (iii) to reach a differential, astrometric precision beyond single-telescope limits sufficient for studying the radial disk structure. Our data support the existence of a radius-dependent disk density perturbation, typically used to explain slow variations of Be-disk hydrogen line profiles.
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J-U. Pott, J. Woillez, S. Ragland, P. L. Wizinowich, J. A. Eisner, J. D. Monnier, R. L. Akeson, A. M. Ghez, J. R. Graham, L. A. Hillenbrand, R. Millan-Gabet, E. Appleby, B. Berkey, M. M. Colavita, A. Cooper, C. Felizardo, J. Herstein, M. Hrynevych, D. Medeiros, D. Morrison, T. Panteleeva, B. Smith, K. Summers, K. Tsubota, C. Tyau, and E. Wetherell "First Keck Interferometer measurements in self-phase referencing mode: spatially resolving circum-stellar line emission of 48 Lib", Proc. SPIE 7734, Optical and Infrared Interferometry II, 77340P (21 July 2010); doi: 10.1117/12.856922; https://doi.org/10.1117/12.856922
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