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מאמרים קשורים
Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars
We present interferometric angular sizes for 12 stars with knownplanetary companions, for comparison with 28 additional main-sequencestars not known to host planets. For all objects we estimate bolometricfluxes and reddenings through spectral-energy distribution (SED) fits,and in conjunction with the angular sizes, measurements of effectivetemperature. The angular sizes of these stars are sufficiently smallthat the fundamental resolution limits of our primary instrument, thePalomar Testbed Interferometer, are investigated at thesub-milliarcsecond level and empirically established based upon knownperformance limits. We demonstrate that the effective temperature scaleas a function of dereddened (V – K)0 color isstatistically identical for stars with and without planets. A usefulbyproduct of this investigation is a direct calibration of the TEFF scale for solarlike stars, as a function of both spectraltype and (V – K)0 color, with an precision of\overline{\Delta T}_{\it {(V-K)}_0} = 138\,K over the range (V –K)0 = 0.0-4.0 and \overline{\Delta T}_{SpType} = 105\,K forthe range F6V-G5V. Additionally, in an Appendix we provide SED fits forthe 166 stars with known planets which have sufficient photometryavailable in the literature for such fits; this derived "XO-Rad"database includes homogeneous estimates of bolometric flux, reddening,and angular size.
| Extrasolar Giant Planets and X-Ray Activity
We have carried out a survey of X-ray emission from stars with giantplanets, combining both archival and targeted surveys. Over 230 starshave been currently identified as possessing planets, and roughlyone-third of these have been detected in X-rays. We carry out detailedstatistical analysis on a volume-limited sample of main-sequence starsystems with detected planets, comparing subsamples of stars that haveclose-in planets with stars that have more distant planets. Thisanalysis reveals strong evidence that stars with close-in giant planetsare on average more X-ray active by a factor of ~4 than those withplanets that are more distant. This result persists for various sampleselections. We find that even after accounting for observational samplebias, a significant residual difference still remains. Thisobservational result is consistent with the hypothesis that giantplanets in close proximity to the primary stars influence the stellarmagnetic activity.
| The CORALIE survey for southern extra-solar planets. XV. Discovery of two eccentric planets orbiting HD 4113 and HD 156846
We report the detection of two very eccentric planets orbitingHD 4113 and HD 156846 with theCORALIE Echelle spectrograph mounted on the 1.2-m Euler Swiss telescopeat La Silla. The first planet, HD 4113 b, has minimum mass of msin{i}=1.6 ± 0.2 M_Jup, a period of P=526.59 ± 0.21 daysand an eccentricity of e=0.903 ± 0.02. It orbits a metal rich G5Vstar at a=1.28 AU, which displays an additional radial velocity drift of28 m s-1 yr-1 observed during 8 years. Thecombination of the radial-velocity data and the non-detection of anymain sequence stellar companion in our high contrast images, taken atthe VLT with NACO/SDI, characterizes the companion as a probable browndwarf or as a faint white dwarf. The second planet, HD 156846b, has minimum mass of m sin{i}=10.45 ± 0.05 M_Jup, aperiod of P=359.51 ± 0.09 days, an eccentricity of e=0.847± 0.002 and is located at a=1.0 AU from its parent star.HD 156846 is a metal rich G0 dwarf and is also theprimary of a wide binary system (a>250 AU, P>4000 years). Itsstellar companion, IDS 17147-1914 B, is a M4 dwarf.The very high eccentricities of both planets can be explained by Kozaioscillations induced by the presence of a third object.
| 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.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| 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
| Mining the Metal-rich Stars for Planets
We examine the correlation between stellar metallicity and the presenceof short-period planets. It appears that approximately 1% of dwarf starsin the solar neighborhood harbor short-period planets characterized bynear-circular orbits and orbital periods P<20 days. However, amongthe most metal-rich stars (defined as having [Fe/H]>0.2 dex), itappears that the fraction increases to 10%. Using the Hipparcos databaseand the Hauck & Mermilliod compilation of Strömgren uvbyphotometry, we identify a sample of 206 metal-rich stars of spectraltype K, G and F which have an enhanced probability of harboringshort-period planets. Many of these stars would be excellent candidatesfor addition to radial velocity surveys. We have searched the Hipparcosepoch photometry for transiting planets within our 206 star catalog. Wefind that the quality of the Hipparcos data is not high enough to permitunambiguous transit detections. It is, however, possible to identifycandidate transit periods. We then discuss various ramifications of thestellar metallicity-planet connection. First, we show that there ispreliminary evidence for increasing metallicity with increasing stellarmass among known planet-bearing stars. This trend can be explained by ascenario in which planet-bearing stars accrete an average of 30M⊕ of rocky material after the gaseous protoplanetarydisk phase has ended. We present dynamical calculations which suggestthat a survey of metallicities of spectroscopic binary stars can be usedto understand the root cause of the stellar metallicity-planetconnection.
| Correspondences Between Bruce Proper Motion Survey and the Bonnerdurchmusterung
Not Available
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לינקים קשורים
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משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | פסל |
| התרוממות ימנית: | 00h43m12.60s |
| סירוב: | -37°58'57.4" |
| גודל גלוי: | 7.889 |
| מרחק: | 44.053 פארסק |
| תנועה נכונה: | 50.5 |
| תנועה נכונה: | -110.8 |
| B-T magnitude: | 8.776 |
| V-T magnitude: | 7.963 |
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