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Stellar Diameters and Temperatures. III. Main-sequence A, F, G, and K Stars: Additional High-precision Measurements and Empirical Relations
von Braun, Kaspar; White, Russel; Goldfinger, P. J. +13 more
Based on CHARA Array measurements, we present the angular diameters of 23 nearby, main-sequence stars, ranging from spectral types A7 to K0, 5 of which are exoplanet host stars. We derive linear radii, effective temperatures, and absolute luminosities of the stars using Hipparcos parallaxes and measured bolometric fluxes. The new data are combined…
Distance and Kinematics of the TW Hydrae Association from Parallaxes
Weinberger, Alycia J.; Anglada-Escudé, Guillem; Boss, Alan P.
From common proper motion and signatures of youth, researchers have identified about 30 members of a putative TW Hydrae Association. Only four of these had parallactic distances from Hipparcos. We have measured parallaxes and proper motions for 14 primary members. We combine these with literature values of radial velocities to show that the Galact…
HD 140283: A Star in the Solar Neighborhood that Formed Shortly after the Big Bang
Schaefer, Gail H.; Nelan, Edmund P.; Bond, Howard E. +2 more
HD 140283 is an extremely metal-deficient and high-velocity subgiant in the solar neighborhood, having a location in the Hertzsprung-Russell diagram where absolute magnitude is most sensitive to stellar age. Because it is bright, nearby, unreddened, and has a well-determined chemical composition, this star avoids most of the issues involved in age…
Young Stars near Earth: The Octans-Near Association and Castor Moving Group
Zuckerman, B.; Song, Inseok; Schneider, Adam +1 more
All cataloged stellar moving groups and associations with ages <=100 Myr and within 100 pc of Earth have Galactic space motions (UVW) situated in a "good box" with dimensions ~20 km s-1 on a side. Torres et al. defined the Octans Association as a group of 15 stars with age "20 Myr?" and located ~140 pc from Earth, but with average V …
The Age and Stellar Parameters of the Procyon Binary System
Liebert, James; Williams, Kurtis A.; Fontaine, Gilles +2 more
The Procyon AB binary system (orbital period 40.838 yr, a newly refined determination) is near and bright enough that the component radii, effective temperatures, and luminosities are very well determined, although more than one possible solution to the masses has limited the claimed accuracy. Preliminary mass determinations for each component are…
A Non-LTE Analysis of the Hot Subdwarf O Star BD+28°4211. I. The UV Spectrum
Latour, M.; Chayer, P.; Fontaine, G. +1 more
We present a detailed analysis of the UV spectrum of the calibration star BD+28°4211 using high-quality spectra obtained with the Hubble Space Telescope and Far-Ultraviolet Spectroscopic Explorer satellites. To this aim, we compare quantitatively the observed data with model spectra obtained from state-of-the-art non-LTE metal line-blanketed model…
Distance and Proper Motion Measurement of the Red Supergiant, PZ Cas, in Very Long Baseline Interferometry H2O Maser Astrometry
Asaki, Y.; Imai, H.; Oyama, T. +1 more
We present the very long baseline interferometry H2O maser monitoring observations of the red supergiant, PZ Cas, at 12 epochs from 2006 April to 2008 May. We fitted maser motions to a simple model composed of a common annual parallax and linear motions of the individual masers. The maser motions with the parallax subtracted were well m…
The Pulsation Mode of the Cepheid Polaris
Kovtyukh, V. V.; Usenko, I. A.; Turner, D. G. +1 more
A previously derived photometric parallax of 10.10 ± 0.20 mas, d = 99 ± 2 pc, is confirmed for Polaris by a spectroscopic parallax derived using line ratios in high dispersion spectra for the Cepheid. The resulting estimates for the mean luminosity of langMV rang = -3.07 ± 0.01 s.e., average effective temperature of langT eff…
The 2011 Periastron Passage of the Be Binary δ Scorpii
Okazaki, A. T.; Miroshnichenko, A. S.; Pasechnik, A. V. +19 more
We describe the results of the world-wide observing campaign of the highly eccentric Be binary system δ Scorpii 2011 periastron passage which involved professional and amateur astronomers. Our spectroscopic observations provided a precise measurement of the system orbital period at 10.8092 ± 0.0005 yr. Fitting of the He II 4686 Å line radial veloc…
Dusty OB Stars in the Small Magellanic Cloud. II. Extragalactic Disks or Examples of the Pleiades Phenomenon?
Sandstrom, Karin M.; Bolatto, Alberto D.; Simon, Joshua D. +6 more
We use mid-infrared Spitzer spectroscopy and far-infrared Herschel photometry for a sample of 20 main sequence O9-B2 stars in the Small Magellanic Cloud (SMC) with strong 24 µm excesses to investigate the origin of the mid-IR emission. Either debris disks around the stars or illuminated patches of dense interstellar medium (ISM) can cause su…