Kenneth J. Johnston

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Vega, the second brightest star in the northern hemisphere, serves as a primary spectral type standard. Although its spectrum is dominated by broad hydrogen lines, the narrower lines of the heavy elements suggested slow to moderate rotation, giving confidence that the ground-based calibration of its visible spectrum could be safely extrapolated into the(More)
Precision astrometry at microarcsecond accuracy has application to a wide range of astrophysical problems. This paper is a study of the science questions that can be addressed using an instrument with flexible scheduling that delivers parallaxes at about 4 microarcsec (µas) on targets as faint as V = 20, and differential accuracy of 0.6 µas on bright(More)
We present direct measurements of the limb-darkened intensity profiles of the late-type giant stars HR 5299, HR 7635, and HR 8621 obtained with the Navy Prototype Optical Interferometer (NPOI) at the Lowell Observatory. A triangle of baselines with lengths of 18.9 m, 22.2 m, and 37.5 m was used. We utilized squared visibility amplitudes beyond the first(More)
The golden age of astrophysics is upon us with both grand discoveries (extra-solar planets, dark matter, dark energy) and precision cosmology. Here we argue that fundamental understanding of the working of stars and galaxies is within reach, thanks to the precision measurements that are now becoming possible. We highlight the importance of micro-arcsecond(More)
The first section of this bibliography includes papers presented at conferences and meetings by RLE faculty, staff and students during 1987, and is in chronological order by the month the conference was held. Reprints of papers may be obtained by contacting the authors directly. Sections 30.2 and 30.3 are alphabetical listings by author of journal articles(More)
We present light curves for 149 sources monitored with the Green Bank Interferometer. The light curves are at two radio frequencies (approximately 2.5 and 8.2 GHz) and range from 3 to 15 yrs in length, covering the interval 1979–1996, and have a typical sampling of one flux density measurement every 2 days. We have used these light curves to conduct various(More)
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