2,267 research outputs found

    A Planetary Companion to gamma Cephei A

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    We report on the detection of a planetary companion in orbit around the primary star of the binary system γ\gamma Cephei. High precision radial velocity measurements using 4 independent data sets spanning the time interval 1981--2002 reveal long-lived residual radial velocity variations superimposed on the binary orbit that are coherent in phase and amplitude with a period or 2.48 years (906 days) and a semi-amplitude of 27.5 m s1^{-1}. We performed a careful analysis of our Ca II H & K S-index measurements, spectral line bisectors, and {\it Hipparcos} photometry. We found no significant variations in these quantities with the 906-d period. We also re-analyzed the Ca II λ\lambda8662 {\AA} measurements of Walker et al. (1992) which showed possible periodic variations with the ``planet'' period when first published. This analysis shows that periodic Ca II equivalent width variations were only present during 1986.5 -- 1992 and absent during 1981--1986.5. Furthermore, a refined period for the Ca II λ\lambda8662 {\AA} variations is 2.14 yrs, significantly less than residual radial velocity period. The most likely explanation of the residual radial velocity variations is a planetary mass companion with MM sin ii = 1.7 MJupiterM_{Jupiter} and an orbital semi-major axis of a2a_2 == 2.13 AU. This supports the planet hypothesis for the residual radial velocity variations for γ\gamma Cep first suggested by Walker et al. (1992). With an estimated binary orbital period of 57 years γ\gamma Cep is the shortest period binary system in which an extrasolar planet has been found. This system may provide insights into the relationship between planetary and binary star formation.Comment: 19 pages, 15 figures, accepted in Ap. J. Includes additional data and improved orbital solutio

    Evidence for a Long-period Planet Orbiting Epsilon Eridani

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    High precision radial velocity (RV) measurements spanning the years 1980.8--2000.0 are presented for the nearby (3.22 pc) K2 V star ϵ\epsilon Eri. These data, which represent a combination of six independent data sets taken with four different telescopes, show convincing variations with a period of \approx 7 yrs. A least squares orbital solution using robust estimation yields orbital parameters of period, PP = 6.9 yrs, velocity KK-amplitude == 19 {\ms}, eccentricity ee == 0.6, projected companion mass MM sin ii = 0.86 MJupiterM_{Jupiter}, and semi-major axis a2a_2 == 3.3 AU. Ca II H&K S-index measurements spanning the same time interval show significant variations with periods of 3 and 20 yrs, yet none at the RV period. If magnetic activity were responsible for the RV variations then it produces a significantly different period than is seen in the Ca II data. Given the lack of Ca II variation with the same period as that found in the RV measurements, the long-lived and coherent nature of these variations, and the high eccentricity of the implied orbit, Keplerian motion due to a planetary companion seems to be the most likely explanation for the observed RV variations. The wide angular separation of the planet from the star (approximately 1 arc-second) and the long orbital period make this planet a prime candidate for both direct imaging and space-based astrometric measurements.Comment: To appear in Astrophysical Journal Letters. 9 pages, 2 figure

    Ectoplasm & Superspace Integration Measure for 2D Supergravity with Four Spinorial Supercurrents

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    Building on a previous derivation of the local chiral projector for a two dimensional superspace with eight real supercharges, we provide the complete density projection formula required for locally supersymmetrical theories in this context. The derivation of this result is shown to be very efficient using techniques based on the Ectoplasmic construction of local measures in superspace.Comment: 18 pages, LaTeX; V2: minor changes, typos corrected, references added; V3: version to appear in J. Phys. A: Math. Theor., some comments and references added to address a referee reques

    A qualitative study to explore communication skills in veterinary medical education

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    OBJECTIVE: To explore and gain an understanding of what "clinical communication skills" mean to veterinarians working in private practice and what implications this might have for veterinary medical education. METHODS: Qualitative research methods were used to purposefully sample a range of veterinary practitioners from a pool of South Australian veterinary practices who were interviewed to determine their understanding of what communication skills mean in the context of veterinary practice. Interviews were conducted with fourteen veterinary practitioners. Participants were sampled from a range of ages, veterinary schools of graduation plus urban and rural locations. Interview transcripts were analysed for themes, definitions and contexts. RESULTS: Participants' accounts included a number of skills which they considered to be "communication". Some of the definitions of these skills parallel communication skills and competencies for human medicine on which communication skills training incorporated into veterinary curricula to date have largely been based. However, the veterinarians in this study also raised interesting contextual differences unique to the veterinary profession, such as communication with the animal, selling service, discussing money in relation to decisions for care, and communicating about euthanasia. CONCLUSIONS: Veterinary practitioners require high level communication skills. Education and training in veterinary medicine may be better tailored to reflect the unique context of the veterinary profession.Wendy J. Hamood, Anna Chur-Hansen, Michelle L. McArthu

    Reference soils of south-western Australia

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    First printed 1991, Reprinted 2004https://researchlibrary.agric.wa.gov.au/books/1003/thumbnail.jp

    Darboux Transformations for Supersymmetric Korteweg - de Vries Equations

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    \hspace{.2in}We consider the Darboux type transformations for the spectral problems of supersymmetric KdV systems. The supersymmetric analogies of Darboux and Darboux-Levi transformations are established for the spectral problems of Manin-Radul-Mathieu sKdV and Manin-Radul sKdV. Several B\"acklund transformations are derived for the MRM sKdV and MR sKdV systems.Comment: Latex, 8 pages AS-ITP-94-4

    The Extrasolar Planet epsilon Eridani b - Orbit and Mass

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    Hubble Space Telescope observations of the nearby (3.22 pc), K2 V star epsilon Eridani have been combined with ground-based astrometric and radial velocity data to determine the mass of its known companion. We model the astrometric and radial velocity measurements simultaneously to obtain the parallax, proper motion, perturbation period, perturbation inclination, and perturbation size. Because of the long period of the companion, \eps b, we extend our astrometric coverage to a total of 14.94 years (including the three year span of the \HST data) by including lower-precision ground-based astrometry from the Allegheny Multichannel Astrometric Photometer. Radial velocities now span 1980.8 -- 2006.3. We obtain a perturbation period, P = 6.85 +/- 0.03 yr, semi-major axis, alpha =1.88 +/- 0.20 mas, and inclination i = 30.1 +/- 3.8 degrees. This inclination is consistent with a previously measured dust disk inclination, suggesting coplanarity. Assuming a primary mass M_* = 0.83 M_{\sun}, we obtain a companion mass M = 1.55 +/- 0.24 M_{Jup}. Given the relatively young age of epsilon Eri (~800 Myr), this accurate exoplanet mass and orbit can usefully inform future direct imaging attempts. We predict the next periastron at 2007.3 with a total separation, rho = 0.3 arcsec at position angle, p.a. = -27 degrees. Orbit orientation and geometry dictate that epsilon Eri b will appear brightest in reflected light very nearly at periastron. Radial velocities spanning over 25 years indicate an acceleration consistent with a Jupiter-mass object with a period in excess of 50 years, possibly responsible for one feature of the dust morphology, the inner cavity
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