Diameters of delta Cephei and eta Aquilae Measured with the Navy Prototype Optical Interferometer

Abstract

We have measured the diameters of the Cepheid variables delta Cephei (18 nights) and eta Aquilae (11 nights) with the Navy Prototype Optical Interferometer. The primary results of these observations are the mean angular diameters <theta(LD)> of these Cepheids: 1.520 +/- 0.014 milliseconds of arc (mas) for delta Cep and 1.69 +/- 0.04 mas for eta Aql. We also report limb-darkened diameters for the check stars in this program: for beta Lac, theta(LD) = 1.909 +/- 0.011 mas, and for 12 Aql, theta(LD) = 2.418 +/- 0.010 mas. When combined with radius estimates from period-radius relations in the literature, the Cepheid angular diameters suggest distances slightly smaller than, but still consistent with, the Hipparcos distances. Pulsations are weakly detected at a level of about 1.5 sigma to 2 sigma for both Cepheids.

15 pages, including one figure; LaTeX 2e; uses aastex, aas_symbols, natbib; accepted for publication in the Astronomical Journal

References in corpus (2)

• Astrophysical Quantities of Cepheid Variables Measured with the NPOI
• Cepheid Period-Radius and Period-Luminosity Relations and the Distance to the LMC

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