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Dynamical and Observational Constraints on Additional Planets in Highly Eccentric Planetary Systems
Long time coverage and high radial velocity precision have allowed forthe discovery of additional objects in known planetary systems. Many ofthe extrasolar planets detected have highly eccentric orbits, whichraises the question of how likely those systems are to host additionalplanets. We investigate six systems which contain a very eccentric(e>0.6) planet: HD 3651, HD 37605, HD 45350, HD 80606, HD 89744, and16 Cyg B. We present updated radial velocity observations and orbitalsolutions, search for additional planets, and perform test-particlesimulations to find regions of dynamical stability. The dynamicalsimulations show that short-period planets could exist in the HD 45350and 16 Cyg B systems, and we use the observational data to set tightdetection limits, which rule out additional planets down to a fewNeptune masses in the HD 3651, HD 45350, and 16 Cyg B systems.Based on observations obtained with the Hobby-Eberly Telescope, which isa joint project of the University of Texas at Austin, Pennsylvania StateUniversity, Stanford University, Ludwig-Maximilians-UniversitätMünchen, and Georg-August-Universität Göttingen.
| The HARPS search for southern extra-solar planets. IX. Exoplanets orbiting HD 100777, HD 190647, and HD 221287
Context: The HARPS high-resolution high-accuracy spectrograph was madeavailable to the astronomical community in the second half of 2003.Since then, we have been using this instrument for monitoring radialvelocities of a large sample of Solar-type stars (≃1400 stars) inorder to search for their possible low-mass companions. Aims: Amongstthe goals of our survey, one is to significantly increase the number ofdetected extra-solar planets in a volume-limited sample to improve ourknowledge of their orbital elements distributions and thus obtain betterconstraints for planet-formation models. Methods: Radial-velocitieswere obtained from high-resolution HARPS spectra via thecross-correlation method. We then searched for Keplerian signals in theobtained radial-velocity data sets. Finally, companions orbiting oursample stars were characterised using the fitted orbital parameters. Results: In this paper, we present the HARPS radial-velocity data andorbital solutions for 3 Solar-type stars: HD 100777,HD 190647, and HD 221287. Theradial-velocity data of HD 100777 is best explainedby the presence of a 1.16 M_Jup planetary companion on a 384-dayeccentric orbit (e = 0.36). The orbital fit obtained for the slightlyevolved star HD 190647 reveals the presence of along-period (P = 1038 d) 1.9 M_Jup planetary companion on a moderatelyeccentric orbit (e = 0.18). HD 221287 is hosting a3.1 M_Jup planet on a 456-day orbit. The shape of this orbit is not verywell-constrained because of our non-optimal temporal coverage andbecause of the presence of abnormally large residuals. We find cluesthat these large residuals result from spectral line-profile variationsprobably induced by processes related to stellar activity.Based on observations made with the HARPS instrument on the ESO 3.6-mtelescope at the La Silla Observatory (Chile) under the GTO programme ID072.C-0488. Tables 2-4 are only available in electronic form athttp://www.aanda.org
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| Effective temperature scale and bolometric corrections from 2MASS photometry
We present a method to determine effective temperatures, angularsemi-diameters and bolometric corrections for population I and II FGKtype stars based on V and 2MASS IR photometry. Accurate calibration isaccomplished by using a sample of solar analogues, whose averagetemperature is assumed to be equal to the solar effective temperature of5777 K. By taking into account all possible sources of error we estimateassociated uncertainties to better than 1% in effective temperature andin the range 1.0-2.5% in angular semi-diameter for unreddened stars.Comparison of our new temperatures with other determinations extractedfrom the literature indicates, in general, remarkably good agreement.These results suggest that the effective temperaure scale of FGK starsis currently established with an accuracy better than 0.5%-1%. Theapplication of the method to a sample of 10 999 dwarfs in the Hipparcoscatalogue allows us to define temperature and bolometric correction (Kband) calibrations as a function of (V-K), [m/H] and log g. Bolometriccorrections in the V and K bands as a function of T_eff, [m/H] and log gare also given. We provide effective temperatures, angularsemi-diameters, radii and bolometric corrections in the V and K bandsfor the 10 999 FGK stars in our sample with the correspondinguncertainties.
| The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of 14 000 F and G dwarfs
We present and discuss new determinations of metallicity, rotation, age,kinematics, and Galactic orbits for a complete, magnitude-limited, andkinematically unbiased sample of 16 682 nearby F and G dwarf stars. Our63 000 new, accurate radial-velocity observations for nearly 13 500stars allow identification of most of the binary stars in the sampleand, together with published uvbyβ photometry, Hipparcosparallaxes, Tycho-2 proper motions, and a few earlier radial velocities,complete the kinematic information for 14 139 stars. These high-qualityvelocity data are supplemented by effective temperatures andmetallicities newly derived from recent and/or revised calibrations. Theremaining stars either lack Hipparcos data or have fast rotation. Amajor effort has been devoted to the determination of new isochrone agesfor all stars for which this is possible. Particular attention has beengiven to a realistic treatment of statistical biases and errorestimates, as standard techniques tend to underestimate these effectsand introduce spurious features in the age distributions. Our ages agreewell with those by Edvardsson et al. (\cite{edv93}), despite severalastrophysical and computational improvements since then. We demonstrate,however, how strong observational and theoretical biases cause thedistribution of the observed ages to be very different from that of thetrue age distribution of the sample. Among the many basic relations ofthe Galactic disk that can be reinvestigated from the data presentedhere, we revisit the metallicity distribution of the G dwarfs and theage-metallicity, age-velocity, and metallicity-velocity relations of theSolar neighbourhood. Our first results confirm the lack of metal-poor Gdwarfs relative to closed-box model predictions (the ``G dwarfproblem''), the existence of radial metallicity gradients in the disk,the small change in mean metallicity of the thin disk since itsformation and the substantial scatter in metallicity at all ages, andthe continuing kinematic heating of the thin disk with an efficiencyconsistent with that expected for a combination of spiral arms and giantmolecular clouds. Distinct features in the distribution of the Vcomponent of the space motion are extended in age and metallicity,corresponding to the effects of stochastic spiral waves rather thanclassical moving groups, and may complicate the identification ofthick-disk stars from kinematic criteria. More advanced analyses of thisrich material will require careful simulations of the selection criteriafor the sample and the distribution of observational errors.Based on observations made with the Danish 1.5-m telescope at ESO, LaSilla, Chile, and with the Swiss 1-m telescope at Observatoire deHaute-Provence, France.Complete Tables 1 and 2 are only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/989
| Stroemgren photometry of F- and G-type stars brighter than V = 9.6. I. UVBY photometry
Within the framework of a large photometric observing program, designedto investigate the Galaxy's structure and evolution, Hβ photometryis being made for about 9000 stars. As a by-product, supplementary uvbyphotometry has been made. The results are presented in a cataloguecontaining 6924 uvby observations of 6190 stars, all south ofδ=+38deg. The overall internal rms errors of one observation(transformed to the standard system) of a program star in the interval6.5
| The chemical evolution of the solar neighborhood. I - A bias-free reduction technique and data sample
The possible ways of measuring the age-metallicity relation for thegalactic disk in the neighborhood of the sun are discussed. It is shownthat the use of a field star sample chosen on the basis of effectivetemperature introduces a bias which results in a monotonic increase inthe metal abundance of the disk with time. However, if theage-metallicity relation for the disk can be shown to satisfy certaincriteria, the bias introduced in such a sample can be neglected: thegalactic disk apparently satisfies the criteria. It is concluded that asample analyzed through the use of uvby and H(beta) photometry inconjunction with a self-consistent set of theoretical isochronesprovides the least biased, most accurate estimate of the age-metallicityrelation for the disk.
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Pozíciós és asztrometriai adatok
| Csillagkép: | Tukán |
| Rektaszcenzió: | 23h31m20.34s |
| Deklináció: | -58°12'35.0" |
| Vizuális fényesség: | 7.816 |
| Távolság: | 52.882 parszek |
| RA sajátmozgás: | 183.7 |
| Dec sajátmozgás: | -4.8 |
| B-T magnitude: | 8.414 |
| V-T magnitude: | 7.866 |
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