Search Publications
Absolute Dimensions of the M-Type Eclipsing Binary YY Geminorum (Castor C): A Challenge to Evolutionary Models in the Lower Main Sequence
Torres, Guillermo; Ribas, Ignasi
We present new spectroscopic observations of the detached late-type double-lined eclipsing binary YY Geminorum (P=0.814 day), a member of the Castor sextuple system and one of the benchmarks for the comparison between observations and stellar evolution theory in the lower main sequence. In addition, we have reanalyzed existing light curves in seve…
Discovery of a Substellar Companion to the K2 III Giant ι Draconis
Butler, R. Paul; Fischer, Debra A.; Marcy, Geoffrey W. +3 more
We report precise radial velocity measurements of the K giant ι Dra (HD 137759, HR 5744, HIP 75458), carried out at Lick Observatory, which reveal the presence of a substellar companion orbiting the primary star. A Keplerian fit to the data yields an orbital period of about 536 days and an eccentricity of 0.70. Assuming a mass of 1.05 Msolar<…
Ten Low-Mass Companions from the Keck Precision Velocity Survey
Butler, R. Paul; Vogt, Steven S.; Fischer, Debra A. +4 more
Ten new companions have emerged from the Keck precision Doppler velocity survey, with minimum (Msini) masses ranging from 0.8 MJUP to 0.34 Msolar. Five of these are planet candidates with Msini<12 MJUP, two are brown dwarf candidates with Msini~30 MJUP, and three are low-mass stellar companions. Hippa…
A Second Planet Orbiting 47 Ursae Majoris
Butler, R. Paul; Vogt, Steven S.; Fischer, Debra A. +2 more
Precise Doppler velocity measurements during 13 yr at Lick Observatory reveal the presence of two planets orbiting the star 47 UMa. The previously detected inner planet is confirmed by the newer velocities that yield a revised orbital period Pb=1089.0+/-2.9 days, Msini=2.54 MJ, and eccentricity eb=0.061+/-0.014. Th…
K-Band Red Clump Distance to the Large Magellanic Cloud
Minniti, Dante; Rejkuba, Marina; Alves, David R. +1 more
The Hipparcos I-band calibration of horizontal-branch red clump giants as standard candles has lead to controversial results for the distance to the Large Magellanic Cloud (LMC). In an attempt to properly ascertain the corrections for interstellar extinction and clump age and metallicity, we analyze new multiwavelength luminosity functions of the …
The Velocity Distribution of the Nearest Interstellar Gas
Welty, Daniel E.; Frisch, Priscilla C.; Grodnicki, Lauren
The bulk flow velocity for the cluster of interstellar cloudlets within ~30 pc of the Sun is determined from optical and ultraviolet absorption line data, after omitting from the sample stars with circumstellar disks or variable emission lines and the active variable HR 1099. A total of 96 velocity components toward the remaining 60 stars yield a …
Rotation and Activity in the Solar-Metallicity Open Cluster NGC 2516
Pinsonneault, Marc; Sills, Alison; Jeffries, Robin D. +3 more
We report new measures of radial velocities and rotation rates (vsini) for 51 F and early G stars in the open cluster NGC 2516 and combine these with previously published data. From high signal-to-noise ratio spectra of two stars, we show that NGC 2516 has a relative iron abundance with respect to the Pleiades of Δ[Fe/H]=+0.04+/-0.07 at the canoni…
On the Distance of Magellanic Clouds: First Overtone Cepheids
Marconi, M.; Bono, G.; Caputo, F. +1 more
We present a detailed comparison between predicted and empirical PLI,K relations and the Wesenheit function for Galactic and Magellanic Cloud (MC) first overtone (FO) Cepheids. We find that zero points predicted by Galactic Cepheid models based on a noncanonical (mild overshooting) mass-luminosity (ML) relation are in very good agreemen…
Tomographic Separation of Composite Spectra. VIII. The Physical Properties of the Massive Compact Binary in the Triple Star System HD 36486 (δ Orionis A)
Gies, Douglas R.; Penny, Laura R.; Bagnuolo, William G., Jr. +2 more
We present the first double-lined spectroscopic orbital elements for the central binary in the massive triple δ Orionis A. The solutions are based on fits of cross-correlation functions of IUE high-dispersion UV spectra and He I λ6678 profiles. The orbital elements for the primary agree well with previous results, and in particular, we confirm the…
Resolving the 47 Tucanae Distance Problem
Salaris, Maurizio; Kilkenny, David; van Wyk, Francois +1 more
We present new B-, V-, and I-band photometry for a sample of 43 local subdwarfs with Hipparcos parallax errors less than 13%, in the metallicity range -1.0<[Fe/H]<-0.3, which we use to perform main-sequence (MS) fitting to the Galactic globular cluster 47 Tuc. This sample is many times larger than those used in previous MS-fitting studies an…