24 July 1998 Observations of stellar limb darkening with the Navy Prototype Optical Interferometer
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Abstract
We present results of an on-going program to measure limb- darkened angular diameters of late-type giant stars using the Navy Prototype Optical Interferometer (NPOI). Observing with three elements of the NPOI and using twenty spectral channels covering the wavelength range from 520 nm to 850 nm we are able to extend the spatial frequency coverage beyond the first null in the stellar visibility function for a number of K giants. These observations make use of the technique of phase bootstrapping in which the shorter baselines with high visibilities are used to keep the longer baselines in phase. The data are inconsistent with a uniform brightness stellar disk. Adopting a particular limb- darkening model enables us to derive an angular diameter with high precision. The total uncertainty is dominated by our knowledge of the wavelength scale. These observations also include measurements of the closure phase, which shows a jump of 180 degrees at the position of the first null in the visibility amplitude. This is the first time a non-zero closure phase has been measured on a single star with a separate element optical interferometer.
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Thomas A. Pauls, Thomas A. Pauls, David Mozurkewich, David Mozurkewich, J. Thomas Armstrong, J. Thomas Armstrong, Christian A. Hummel, Christian A. Hummel, James A. Benson, James A. Benson, Arsen R. Hajian, Arsen R. Hajian, "Observations of stellar limb darkening with the Navy Prototype Optical Interferometer", Proc. SPIE 3350, Astronomical Interferometry, (24 July 1998); doi: 10.1117/12.317112; https://doi.org/10.1117/12.317112
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