Search Publications
A Planetary Companion to γ Cephei A
Cochran, William D.; Endl, Michael; Hatzes, Artie P. +5 more
We report on the detection of a planetary companion in orbit around the primary star of the binary system γ Cephei. High-precision radial velocity measurements using four independent data sets spanning the time interval 1981-2002 reveal long-lived residual radial velocity variations superposed on the binary orbit that are coherent in phase and amp…
New Members of the TW Hydrae Association, β Pictoris Moving Group, and Tucana/Horologium Association
Zuckerman, B.; Song, Inseok; Bessell, M. S.
We have identified five new members of the TW Hydrae association (TWA), 11 new members of the β Pic moving group, and 11 new Tucana/Horologium association members. These are the three youngest (<~30 Myr) known kinematic stellar groups near the Earth. Newly identified β Pic group members are located mostly in the northern hemisphere, and they ha…
The Oort Constants Measured from Proper Motions
Olling, Rob P.; Dehnen, Walter
The Oort constants describe the local spatial variations of the stellar streaming field. The classic way for their determination employs their effect on stellar proper motions. We discuss various problems arising in this procedure. A large, hitherto apparently overlooked, source of potential systematic error arises from longitudinal variations of …
Transit Target Selection Using Reduced Proper Motions
Gould, Andrew; Morgan, Christopher W.
In searches for planetary transits in the field, well over half of the survey stars are typically giants or other stars that are too large to permit straightforward detection of planets. For all-sky searches of bright V<~11 stars, the fraction is ~90%. We show that the great majority of these contaminants can be removed from the sample by analy…
Improved Astrometry and Photometry for the Luyten Catalog. I. Bright Stars
Gould, Andrew; Salim, Samir
We outline the construction of a refined version of the New Luyten Two-Tenths (NLTT) catalog of high proper motion stars, which will contain improved astrometry and photometry for the vast majority of the ~59,000 stars in NLTT. The bright end is constructed by matching NLTT stars to Hipparcos, Tycho-2, and Starnet; the faint end by matching to USN…
Stellar Hydrodynamics in Radiative Regions
Rigby, Jane R.; Knierman, Karen A.; Young, Patrick A. +1 more
We present an analysis of the response of a radiative region to waves generated by a convective region of the star; this wave treatment of the classical problem of ``overshooting'' gives extra mixing relative to the treatment traditionally used in stellar evolutionary codes. The interface between convectively stable and unstable regions is dynamic…
ROSAT View of Hipparcos F Stars
Makarov, V. V.; Voges, W.; Suchkov, A. A.
For a set of 11,900 F stars that have uvby photometry and are in the Hipparcos catalog, we have found 1980 X-ray counterparts (~17%) in the ROSAT All-Sky Survey (RASS). In this paper we analyze X-ray properties of these ROSAT F stars and compare that sample with the entire set of our F stars. The comparison has shown that the ROSAT F stars are on …
Oxygen Abundance in the Template Halo Giant HD 122563
Damineli, Augusto; Hill, Vanessa; Meléndez, Jorge +7 more
HD 122563 is a well-known bright (V=6.2) halo giant of low metallicity ([Fe/H]~-2.7). We have observed HD 122563 for infrared OH lines at 1.5-1.7 µm in the H band with the NIRSPEC high-resolution spectrograph at the 10 m Keck Telescope. Optical spectra were obtained with the UVES spectrograph at the 8 m VLT UT2 telescope at ESO (Paranal) and…
The Distance to the Large Magellanic Cloud Cluster NGC 1866 and the Surrounding Field
Salaris, M.; Walker, A. R.; Brocato, E. +2 more
We use the main-sequence stars in the LMC cluster NGC 1866 and red clump stars in the local field to obtain two independent estimates of the LMC distance. We apply an empirical main-sequence-fitting technique based on a large sample of subdwarfs with accurate Hipparcos parallaxes in order to estimate the cluster distance modulus, and the multicolo…
Early-Type Stars: Most Favorable Targets for Astrometrically Detectable Planets in the Habitable Zone
Fischer, Debra A.; Gould, Andrew; Ford, Eric B.
Early-type stars appear to be a difficult place to look for planets astrometrically. First, they are relatively heavy, and for fixed planetary mass the astrometric signal falls inversely as the stellar mass. Second, they are relatively rare (and so tend to be more distant), and for fixed orbital separation the astrometric signal falls inversely as…