Results 1 - 10 of 4388
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[en] The radial velocities of 218 star forming regions up to 10 kpc from the Sun are investigated statistically using the cubic approximation of a general two-dimensional velocity field. The departures from circular flow in the Galaxy are mainly connected with complexes of star forming regions 1 to 2 kpc in size. Star forming regions from a complex share a common motion. Complexes are interpreted as a consequence of clumped star formation and subsequent expansion of multi-supernova remnants. The negative velocity departure of complexes P1-P4 from circular motion may be due to the influence of the Perseus spiral arm. (author). 9 figs., 5 tabs., 18 refs
[en] New orbital elements of the secondary component of the Be+K binary AX Monocerotis were derived on the basis of 28 new Ondrejov coude spectrograms of the visual region using also data from former radial velocity measurements reported in the astronomical literature. (author). 1 fig., 4 tabs., 12 refs
[en] We present results of deep direct imaging of the radial velocity (RV) planet-host star 14 Her (=GJ 614, HD 145675), obtained in the L' band with the Clio-2 camera and the MMT adaptive optics system. This star has one confirmed planet and an unconfirmed outer companion, suggested by residuals in the RV data. The orbital parameters of the unconfirmed object are not well constrained since many mass/semimajor axis configurations can fit the available data. The star has been directly imaged several times, but none of the campaigns has ruled out sub-stellar companions. With ∼2.5 hr of integration, we rule out at 5σ confidence ∼>18 MJ companions beyond ∼25 AU, based on the Baraffe et al. COND mass-luminosity models. Combining our detection limits with fits to the RV data and analytic dynamical analysis, we constrain the orbital parameters of 14 Her c to be 3 ∼< m/MJ ∼<42, 7 ∼< a/AU ∼<25, and e ∼< 0.5. A wealth of information can be obtained from RV/direct imaging overlap, especially with deep imaging as this work shows. The collaboration between RV and direct imaging will become more important in the coming years as the phase space probed by each technique converges. Future studies involving RV/imaging overlap should be sure to consider the effects of a potential planet's projected separation, as quoting limits assuming face-on orientation will be misleading.
[en] We present new precise HIRES radial velocity (RV) data sets of five nearby stars obtained at Keck Observatory. HD 31253, HD 218566, HD 177830, HD 99492, and HD 74156 are host stars of spectral classes F through K and show RV variations consistent with new or additional planetary companions in Keplerian motion. The orbital parameters of the candidate planets in the five planetary systems span minimum masses of M sin i = 27.43 M+ to 8.28 MJ, periods of 17.05-4696.95 days and eccentricities ranging from circular to extremely eccentric (e ∼ 0.63). The fifth star, HD 74156, was known to have both a 52 day and a 2500 day planet, and was claimed to also harbor a third planet at 336 days, in apparent support of the 'Packed Planetary System' hypothesis. Our greatly expanded data set for HD 74156 provides strong confirmation of both the 52 day and 2500 day planets, but strongly contradicts the existence of a 336 day planet, and offers no significant evidence for any other planets in the system.
[en] We present new radial velocities from Keck Observatory and both Newtonian and Keplerian solutions for the triple-planet system orbiting HD 37124. The orbital solution for this system has improved dramatically since the third planet was first reported in Vogt et al. with an ambiguous orbital period. The period ambiguity is resolved, and the outer two planets have an apparent period commensurability of 2:1. A dynamical analysis finds both resonant and non-resonant configurations consistent with the radial velocity data and constrains the mutual inclinations of the planets to be <∼300. We discuss HD 37124 in the context of the other 19 exoplanetary systems with apparent period commensurabilities, which we summarize in a table. We show that roughly one in three well-characterized multiplanet systems has a apparent low-order period commensurability, which is more than would naively be expected if the periods of exoplanets in known multiplanet systems were drawn randomly from the observed distribution of planetary orbital periods.
[en] HR 976 has the largest light variation among six Am variables discovered by Winzer. New orbital elements show the same relationship between velocity and light curves that one finds among ellipsoidal variables, and the light range is reasonable for the observed period. This probable identification of the light variation as an ellipsoidal effect makes it likely, but not certain, that the other Am light variables are also ellipsoidal variables
[en] New radial velocities are presented for 35 galaxies in the fields of the Pegasus I and Pegasus II clusters. Many background galaxies with apparent photographic magnitude brighter than 15/sup m/6 are found to be superimposed upon the Pegasus I cluster. Galaxies with radial velocities near the average for the Pegasus II cluster are detected well outside the boundary of the cluster as defined in the Catalogue of Galaxies and Clusters of Galaxies by Zwicky et al. This suggests that the Pegasus II cluster is part of a large cloud of galaxies
[en] We present a new short-period brown dwarf (BD) candidate around the star TYC 1240-00945-1. This candidate was discovered in the first year of the Multi-object APO Radial Velocity Exoplanets Large-area Survey (MARVELS), which is part of the Sloan Digital Sky Survey (SDSS) III, and we designate the BD as MARVELS-1b. MARVELS uses the technique of dispersed fixed-delay interferometery to simultaneously obtain radial velocity (RV) measurements for 60 objects per field using a single, custom-built instrument that is fiber fed from the SDSS 2.5 m telescope. From our 20 RV measurements spread over a ∼370 day time baseline, we derive a Keplerian orbital fit with semi-amplitude K = 2.533 ± 0.025 km s-1, period P = 5.8953 ± 0.0004 days, and eccentricity consistent with circular. Independent follow-up RV data confirm the orbit. Adopting a mass of 1.37 ± 0.11 Msun for the slightly evolved F9 host star, we infer that the companion has a minimum mass of 28.0 ± 1.5 MJup, a semimajor axis 0.071 ± 0.002 AU assuming an edge-on orbit, and is probably tidally synchronized. We find no evidence for coherent intrinsic variability of the host star at the period of the companion at levels greater than a few millimagnitudes. The companion has an a priori transit probability of ∼14%. Although we find no evidence for transits, we cannot definitively rule them out for companion radii ∼<1 RJup.