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Proceedings Paper

Measuring extended structure in stars using the Keck Interferometer Nuller
Author(s): Chris Koresko; M. Mark Colavita; Eugene Serabyn; Andrew Booth; Jean Garcia
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Paper Abstract

The Keck Interferometer Nuller is designed to detect faint off-axis mid-infrared light a few tens to a few hundreds of milliarcseconds from a bright central star. The starlight is suppressed by destructive combination along the long (85 m) baseline, which produces a fringe spacing of 25 mas at a wavelength of 10 μm, with the central null crossing the position of the star. The strong, variable mid-infrared background is subtracted using interferometric phase chopping along the short (5 m) baseline. This paper presents an overview of the observing and data reduction strategies used to produce a calibrated measurement of the off-axis light. During the observations, the instrument cycles rapidly through several calibration and measurement steps, in order to monitor and stabilize the phases of the fringes produced by the various baselines, and to derive the fringe intensity at the constructive peak and destructive null along the long baseline. The data analysis involves removing biases and coherently demodulating the short-baseline fringe with the long-baseline fringe tuned to alternate between constructive and destructive phases, combining the results of many measurements to improve the sensitivity, and estimating the part of the null leakage signal which is associated with the finite angular size of the central star. Comparison of the results of null measurements on science target and calibrator stars permits the instrumental leakage - the "system null leakage" - to be removed and the off-axis light to be measured.

Paper Details

Date Published: 28 June 2006
PDF: 11 pages
Proc. SPIE 6268, Advances in Stellar Interferometry, 626816 (28 June 2006); doi: 10.1117/12.672027
Show Author Affiliations
Chris Koresko, Michelson Science Ctr., California Institute of Technology (United States)
M. Mark Colavita, Jet Propulsion Lab. (United States)
Eugene Serabyn, Jet Propulsion Lab. (United States)
Andrew Booth, Jet Propulsion Lab. (United States)
Jean Garcia, Jet Propulsion Lab. (United States)

Published in SPIE Proceedings Vol. 6268:
Advances in Stellar Interferometry
John D. Monnier; Markus Schöller; William C. Danchi, Editor(s)

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