arXiv subjects

James H. Clark III

Publications and source records attributed to James H. Clark III.

5 recordsLinked to original sources

arXiv2025

Eighteen Exoplanet Host Stars from the NPOI Data Archive

During the course of publishing angular diameters from the Navy Precision Optical Interferometer data archive, we found we had data on 17 confirmed exoplanet host stars and one exoplanet candidate (HD 20902/alpha Per). Here, we update our previously published stellar radii with more precise Gaia parallaxes when available, and use our radius and effective temperature measurements to fit each star's mass and age using MIST models. The mass changed by more than 10% for 9 of the 18 stars. Combining our updated masses, radii, and temperatures, we present refined planetary masses as well as habitable zone calculations.

astro-ph.SR↗

arXiv2025

Vintage NPOI: New and Updated Angular Diameters for 145 Stars

We present new or updated angular diameters, physical radii, and effective temperatures for 145 stars from the Navy Precision Optical Interferometer data archive. We used data from 1996 to late-2021, and we describe the differences between early and late data, which hinge upon an update of the beam combiner in 2002. We came across several sub-categories of stars of interest: 13 of our stars are promising targets for the Habitable World Observatory and therefore require as much study as possible, and 14 more are asteroseismic targets and have stellar masses after we combined our radii and effective temperatures with frequencies of maximum oscillation power values from the literature. In addition to this, many of the stars here show measurements to the first null in the visibility curve and beyond, which is the gateway to determining second-order effects such as direct measurements of limb-darkening. Finally, we consider the stars in the larger context of previous NPOI measurements and find the majority 75% of the angular diameters in the overall NPOI sample have uncertainties of 2% or less.

astro-ph.SR↗

arXiv2025

Simultaneous Six-way Observations from the Navy Precision Optical Interferometer

We measured the angular diameters of six stars using the 6-element observing mode of the Navy Precision Optical Interferometer (NPOI) for the first time since the early 2000s. Four of the diameters ranged from 1.2 mas to 1.9 mas, while the two others were much smaller at approximately 0.5 mas to 0.7 mas, which are the two smallest angular diameters measured to date with the NPOI. There is a larger spread in the measurements than data obtained with 3- or 4- or 5-element modes, which can be attributed in part to the flux imbalance due to the combination of more than 2 siderostats in a single spectrograph, and also to cross talk between multiple baselines related to non-linearities in the fast delay line dither strokes. We plan to address this in the future by using the VISION beam combiner.

astro-ph.SR↗

arXiv2025

Thirty-Three New Stellar Angular Diameters from the NPOI, and Nearly 180 NPOI Diameters as an Ensemble

We present new angular diameter measurements for 33 stars from the Navy Precision Optical Interferometer, reaching uncertainties on the limb-darkened diameter of 2% or less for 21 targets. We also determined the physical radius, bolometric flux, luminosity, and effective temperature for each star. Our sample is a mix of giant, subgiant, and dwarf stars, and span spectral classes from mid-A to to mid-K. We combined these 33 stars with samples from previous publications to analyze how the NPOI diameters compare to those obtained using other means, namely (V-K) color, the JMMC Stellar Diameters Catalog, and Gaia predictions.

astro-ph.SR↗

arXiv2022

Angular Diameters and Fundamental Parameters of Forty-Four Stars from the Navy Precision Optical Interferometer

We measured the angular diameters of 44 stars with the Navy Precision Optical Interferometer, obtaining uncertainties on the limb darkened diameter of 2% or less for all but four stars. We then used our diameters with Gaia or Hipparcos parallaxes to calculate each star's physical radius. We gathered information from the literature to determine bolometric flux and luminosity, and combined that with our diameters to produce an effective temperature. Our sample consists of mostly giant stars, and spans a wide range of spectral classes from B to M.

astro-ph.SR↗