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Two Suns in The Sky: Stellar Multiplicity in Exoplanet Systems
We present results of a reconnaissance for stellar companions to all 131radial velocity-detected candidate extrasolar planetary systems known asof 2005 July 1. Common proper-motion companions were investigated usingthe multiepoch STScI Digitized Sky Surveys and confirmed by matching thetrigonometric parallax distances of the primaries to companion distancesestimated photometrically. We also attempt to confirm or refutecompanions listed in the Washington Double Star Catalog, in the Catalogsof Nearby Stars Series by Gliese and Jahreiß, in Hipparcosresults, and in Duquennoy & Mayor's radial velocity survey. Ourfindings indicate that a lower limit of 30 (23%) of the 131 exoplanetsystems have stellar companions. We report new stellar companions to HD38529 and HD 188015 and a new candidate companion to HD 169830. Weconfirm many previously reported stellar companions, including six starsin five systems, that are recognized for the first time as companions toexoplanet hosts. We have found evidence that 20 entries in theWashington Double Star Catalog are not gravitationally bound companions.At least three (HD 178911, 16 Cyg B, and HD 219449), and possibly five(including HD 41004 and HD 38529), of the exoplanet systems reside intriple-star systems. Three exoplanet systems (GJ 86, HD 41004, andγ Cep) have potentially close-in stellar companions, with planetsat roughly Mercury-Mars distances from the host star and stellarcompanions at projected separations of ~20 AU, similar to the Sun-Uranusdistance. Finally, two of the exoplanet systems contain white dwarfcompanions. This comprehensive assessment of exoplanet systems indicatesthat solar systems are found in a variety of stellar multiplicityenvironments-singles, binaries, and triples-and that planets survive thepost-main-sequence evolution of companion stars.
| Catalog of Nearby Exoplanets
We present a catalog of nearby exoplanets. It contains the 172 knownlow-mass companions with orbits established through radial velocity andtransit measurements around stars within 200 pc. We include fivepreviously unpublished exoplanets orbiting the stars HD 11964, HD 66428,HD 99109, HD 107148, and HD 164922. We update orbits for 83 additionalexoplanets, including many whose orbits have not been revised sincetheir announcement, and include radial velocity time series from theLick, Keck, and Anglo-Australian Observatory planet searches. Both thesenew and previously published velocities are more precise here due toimprovements in our data reduction pipeline, which we applied toarchival spectra. We present a brief summary of the global properties ofthe known exoplanets, including their distributions of orbital semimajoraxis, minimum mass, and orbital eccentricity.Based on observations obtained at the W. M. Keck Observatory, which isoperated jointly by the University of California and the CaliforniaInstitute of Technology. The Keck Observatory was made possible by thegenerous financial support of the W. M. Keck Foundation.
| Dynamical Stability and Habitability of the γ Cephei Binary-Planetary System
It has been suggested that the long-lived residual radial velocityvariations observed in the precision radial velocity measurements of theprimary of γ Cephei (HR 8974, HD 222404, HIP 116727) are likelydue to a Jupiter-like planet orbiting this star. In this paper, thedynamics of this planet is studied, and the possibility of the existenceof a terrestrial planet around its central star is discussed.Simulations, which have been carried out for different values of theeccentricity and semimajor axis of the binary, as well as the orbitalinclination of its Jupiter-like planet, expand on previous studies ofthis system and indicate that, for the values of the binary eccentricitysmaller than 0.5, and for all values of the orbital inclination of theJupiter-like planet ranging from 0° to 40°, the orbit of thisplanet is stable. For larger values of the binary eccentricity, thesystem becomes gradually unstable. Integrations also indicate that,within this range of orbital parameters, a terrestrial planet, such asan Earth-like object, can have a long-term stable orbit only atdistances of 0.3-0.8 AU from the primary star. The habitable zone of theprimary, at a range of approximately 3.05-3.7 AU, is, however, unstable.
| Gas Giant Protoplanets Formed by Disk Instability in Binary Star Systems
Gas giant planets have been discovered in binary or triple star systemswith a range of semimajor axes. We present a new suite ofthree-dimensional radiative gravitational hydrodynamics modelssuggesting that binary stars may be quite capable of forming planetarysystems similar to our own. One difference between the new and previouscalculations is the inclusion of artificial viscosity in the previouswork, leading to significant conversion of disk kinetic energy intothermal energy in shock fronts and elsewhere. New models are presentedshowing how vigorous artificial viscosity can help to suppress clumpformation. The new models with binary companions do not employ anyexplicit artificial viscosity and also include the third (vertical)dimension in the hydrodynamic calculations, allowing for transientphases of convective cooling. The new calculations of the evolution ofinitially marginally gravitationally stable disks show that the presenceof a binary star companion may actually help to trigger the formation ofdense clumps that could become giant planets. Earth-like planets wouldform much later in the inner disk regions by the traditional collisionalaccumulation of progressively larger, solid bodies. We also show that inmodels without binary companions, which begin their evolution asgravitationally stable disks, the disks evolve to form dense rings,which then break up into self-gravitating clumps. The latter modelssuggest that the evolution of any self-gravitating disk with sufficientmass to form gas giant planets is likely to lead to a period of diskinstability, even in the absence of a trigger such as a binary starcompanion.
| A search for wide visual companions of exoplanet host stars: The Calar Alto Survey
We have carried out a search for co-moving stellar and substellarcompanions around 18 exoplanet host stars with the infrared camera MAGICat the 2.2 m Calar Alto telescope, by comparing our images with imagesfrom the all sky surveys 2MASS, POSS I and II. Four stars of the samplenamely HD 80606, 55 Cnc, HD 46375 and BD-10°3166, arelisted as binaries in the Washington Visual Double Star Catalogue (WDS).The binary nature of HD 80606, 55 Cnc, and HD 46375 is confirmed withboth astrometry as well as photometry, thereby the proper motion of thecompanion of HD 46375 was determined here for the first time. We derivedthe companion masses as well as the longterm stability regions foradditional companions in these three binary systems. We can rule outfurther stellar companions around all stars in the sample with projectedseparations between 270 AU and 2500 AU, being sensitive to substellarcompanions with masses down to 60 {MJup} (S/N=3).Furthermore we present evidence that the two components of the WDSbinary BD-10°3166 are unrelated stars, i.e this system isa visual pair. The spectrophotometric distance of the primary (a K0dwarf) is 67 pc, whereas the presumable secondaryBD-10°3166 B (a M4 to M5 dwarf) is located at a distanceof 13 pc in the foreground.
| Chemical Composition of the Planet-harboring Star TrES-1
We present a detailed chemical abundance analysis of the parent star ofthe transiting extrasolar planet TrES-1. Based on high-resolution KeckHIRES and Hobby-Eberly Telescope HRS spectra, we have determinedabundances relative to the Sun for 16 elements (Na, Mg, Al, Si, Ca, Sc,Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Y, and Ba). The resulting averageabundance of <[X/H]>=-0.02+/-0.06 is in good agreement withinitial estimates of solar metallicity based on iron. We compare theelemental abundances of TrES-1 with those of the sample of stars withplanets, searching for possible chemical abundance anomalies. TrES-1appears not to be chemically peculiar in any measurable way. Weinvestigate possible signs of selective accretion of refractory elementsin TrES-1 and other stars with planets and find no statisticallysignificant trends of metallicity [X/H] with condensation temperatureTc. We use published abundances and kinematic information forthe sample of planet-hosting stars (including TrES-1) and severalstatistical indicators to provide an updated classification in terms oftheir likelihood to belong to either the thin disk or the thick disk ofthe Milky Way. TrES-1 is found to be very likely a member of thethin-disk population. By comparing α-element abundances of planethosts and a large control sample of field stars, we also find thatmetal-rich ([Fe/H]>~0.0) stars with planets appear to besystematically underabundant in [α/Fe] by ~0.1 dex with respect tocomparison field stars. The reason for this signature is unclear, butsystematic differences in the analysis procedures adopted by differentgroups cannot be ruled out.
| Bisectors of the cross-correlation function applied to stellar spectra. Discriminating stellar activity, oscillations and planets
Context: .Bisectors of strong, single spectral lines, usually the Fe I6252 line, have traditionally been used to examine the velocity fieldsin stellar atmospheres. This requires high S/N often achieved by summingmany individual spectra. Aims: .We investigate whether bisectorsderived from cross-correlation functions (CCF) of single-exposurespectra can be used to provide information on stellar atmospheres, andwhether they can be used to discriminate between radial velocity changescaused by planets, magnetic activity and oscillations. Methods:.Using a sample of bright stars observed with the HARPS spectrograph, weexamine the shapes of the bisectors of individual strong spectral linesin summed spectra, comparing with similar studies in the literature.Moreover, we examine four different quantitative CCF bisector measuresfor correlations with radial velocity and stellar parameters.Results: .We show that CCF bisector measures can be used forquantitative analysis, employing both the absolute values and thevariations. From absolute values, log g and absolute magnitude can beapproximated, and from the correlations with radial velocity one candistinguish between magnetic activity, oscillations and orbiting planetsas the probable cause of radial velocity variations. We confirm thatdifferent isolated spectral lines show different bisector shapes, evenbetween lines of the same element, calling for caution in trying toderive global stellar properties from the bisector of a CCF. For theactive star HR 1362 we suggest from the bisector shape an extraphotospheric heating caused by the chromosphere of several hundreddegrees. We confirm the fill-in of spectral lines of the Sun taken onthe daylight sky caused by Rayleigh-Brillouin and aerosol scattering,and we show for the first time that the fill-in has an asymmetriccomponent.
| The CORALIE survey for southern extrasolar planets. XIV. HD 142022 b: a long-period planetary companion in a wide binary
We report precise Doppler measurements of HD 142022 obtained during thepast six years with the CORALIE echelle spectrograph at La SillaObservatory together with a few additional observations made recentlywith the HARPS echelle spectrograph. Our radial velocities revealevidence of a planetary companion with an orbital periodP=1928+53-39 days, an eccentricitye=0.53+0.23-0.18, and a velocity semiamplitudeK=92+102-29 m s-1. The inferredcompanion minimum mass is M_2 sin{i}=5.1+2.6-1.5{M}_Jup and the semimajor axis a=3.03 ± 0.05 AU. Only one fullorbital revolution has been monitored yet, and the periastron passagecould not be observed since the star was too low on the horizon. Theeccentricity and velocity semiamplitude remain therefore quite uncertainand the orbital solution is preliminary. HD 142022 is achromospherically inactive K0 dwarf, metal rich relative to the Sun, andis the primary component of a wide binary. HD 142022 b is thus a new"planet in binary" candidate, and its high eccentricity might be due tosecular interactions with the distant stellar companion.
| An extrasolar giant planet in a close triple-star system
Hot Jupiters are gas-giant planets orbiting with periods of 3-9 daysaround Sun-like stars. They are believed to form in a disk of gas andcondensed matter at or beyond ~2.7 astronomical units (AU-the Sun-Earthdistance) from their parent star. At such distances, there exists asufficient amount of solid material to produce a core capable ofcapturing enough gas to form a giant planet. Subsequently, they migrateinward to their present close orbits. Here I report the detection of anunusual hot Jupiter orbiting the primary star of a triple stellarsystem, HD 188753. The planet has an orbital period of 3.35 days and aminimum mass of 1.14 times that of Jupiter. The primary star's mass is1.06 times that of the Sun, 1.06Msolar. The secondary star,itself a binary stellar system, orbits the primary at an averagedistance of 12.3AU with an eccentricity of 0.50. The mass of thesecondary pair is 1.63Msolar. Such a close and massivesecondary would have truncated a disk around the primary to a radius ofonly ~1.3AU (ref. 4) and might have heated it up to temperatures highenough to prohibit giant-planet formation, leaving the origin of thisplanet unclear.
| A link between the semimajor axis of extrasolar gas giant planets and stellar metallicity
The fact that most extrasolar planets found to date are orbitingmetal-rich stars lends credence to the core accretion mechanism of gasgiant planet formation over its competitor, the disc instabilitymechanism. However, the core accretion mechanism is not refined to thepoint of explaining orbital parameters such as the unexpected semimajoraxes and eccentricities. We propose a model that correlates themetallicity of the host star with the original semimajor axis of itsmost massive planet, prior to migration, assuming that the coreaccretion scenario governs giant gas planet formation. The modelpredicts that the optimum regions for planetary formation shift inwardsas stellar metallicity decreases, providing an explanation for theobserved absence of long-period planets in metal-poor stars. We compareour predictions with the available data on extrasolar planets for starswith masses similar to the mass of the Sun. A fitting procedure producesan estimate of what we define as the zero-age planetary orbit (ZAPO)curve as a function of the metallicity of the star. The model hints thatthe lack of planets circling metal-poor stars may be partly caused by anenhanced destruction probability during the migration process, becausethe planets lie initially closer to their central star.
| Gl86B: a white dwarf orbits an exoplanet host star
In this Letter we present our first high-contrast observations of theexoplanet host star Gl86 using NAOS-CONICA (NACO) and its newSimultaneous Differential Imager (SDI) as well as results from NACOspectroscopy. Els et al. found a faint comoving companion located only~2 arcsec east of the exoplanet host star Gl86A. Our high-contrast SDIobservations rule out additional stellar companions from 1 au up to 23au, and are sensitive for faint T-dwarf companions down to 35MJup. We present evidence for orbital motion of Gl86B aroundthe exoplanet host star Gl86A, which finally confirms that this is abound binary system. With the given photometry from Els et al. and theNACO spectroscopy obtained, we prove that the companion Gl86B is a coolwhite dwarf with an effective temperature of 5000 +/- 500 K. This is thefirst confirmed white dwarf companion to an exoplanet host star and thefirst observational confirmation that planets survive thepost-main-sequence evolution (giant phase and planetary nebula) of astar from which they are separated by only one to two dozen astronomicalunits, as expected from theory.
| Cluster Origin of the Triple Star HD 188753 and Its Planet
The recent discovery by M. Konacki of a ``hot Jupiter'' in thehierarchical triple star system HD 188753 challenges establishedtheories of giant planet formation. If the orbital geometry of thetriple has not changed since the birth of the planet, then a disk aroundthe planetary host star would probably have been too compact and too hotfor a Jovian planet to form by the core accretion model or gravitationalcollapse. This paradox is resolved if the star was initially eithersingle or had a much more distant companion. It is suggested here that aclose multistar dynamical encounter transformed this initial state intothe observed triple, an idea that follows naturally if HD 188753 formedin a moderately dense stellar system-perhaps an open cluster-that hassince dissolved. Three distinct types of encounters are investigated.The most robust scenario involves an initially single planetary hoststar that changes places with the outlying member of a preexistinghierarchical triple.
| Precision Radial Velocities of Double-lined Spectroscopic Binaries with an Iodine Absorption Cell
A spectroscopic technique employing an iodine absorption cell(I2) to superimpose a reference spectrum onto a stellarspectrum is currently the most widely adopted approach to obtainprecision radial velocities of solar-type stars. It has been used todetect ~80 extrasolar planets out of ~130 known. Yet in its originalversion, it only allows us to measure precise radial velocities ofsingle stars. In this paper, we present a novel method employing anI2 absorption cell that enables us to accurately determineradial velocities of both components of double-lined binaries. Ourpreliminary results, based on the data from the Keck I telescope andHIRES spectrograph, demonstrate that 20-30 m s-1 radialvelocity precision can be routinely obtained for ``early'' type binaries(F3-F8). For later type binaries, the precision reaches ~10 ms-1. We discuss applications of the technique to stellarastronomy and searches for extrasolar planets in binary systems. Inparticular, we combine the interferometric data collected with thePalomar Testbed Interferometer with our preliminary precision velocitiesof the spectroscopic double-lined binary HD 4676 to demonstrate thatwith such a combination one can routinely obtain masses of the binarycomponents accurate at least at the level of 1.0%.
| The Planet-Metallicity Correlation
We have recently carried out spectral synthesis modeling to determineTeff, logg, vsini, and [Fe/H] for 1040 FGK-type stars on theKeck, Lick, and Anglo-Australian Telescope planet search programs. Thisis the first time that a single, uniform spectroscopic analysis has beenmade for every star on a large Doppler planet search survey. We identifya subset of 850 stars that have Doppler observations sufficient todetect uniformly all planets with radial velocity semiamplitudes K>30m s-1 and orbital periods shorter than 4 yr. From this subsetof stars, we determine that fewer than 3% of stars with-0.5<[Fe/H]<0.0 have Doppler-detected planets. Above solarmetallicity, there is a smooth and rapid rise in the fraction of starswith planets. At [Fe/H]>+0.3 dex, 25% of observed stars have detectedgas giant planets. A power-law fit to these data relates the formationprobability for gas giant planets to the square of the number of metalatoms. High stellar metallicity also appears to be correlated with thepresence of multiple-planet systems and with the total detected planetmass. This data set was examined to better understand the origin of highmetallicity in stars with planets. None of the expected fossilsignatures of accretion are observed in stars with planets relative tothe general sample: (1) metallicity does not appear to increase as themass of the convective envelopes decreases, (2) subgiants with planetsdo not show dilution of metallicity, (3) no abundance variations for Na,Si, Ti, or Ni are found as a function of condensation temperature, and(4) no correlations between metallicity and orbital period oreccentricity could be identified. We conclude that stars with extrasolarplanets do not have an accretion signature that distinguishes them fromother stars; more likely, they are simply born in higher metallicitymolecular clouds.Based on observations obtained at Lick and Keck Observatories, operatedby the University of California, and the Anglo-Australian Observatories.
| Prospects for Habitable ``Earths'' in Known Exoplanetary Systems
We have examined whether putative Earth-mass planets could remainconfined to the habitable zones (HZs) of the 111 exoplanetary systemsconfirmed by 2004 August. We find that in about half of these systemsthere could be confinement for at least the past 1000 Myr, though insome cases only in variously restricted regions of the HZ. The HZmigrates outward during the main-sequence lifetime, and we find that inabout two-thirds of the systems an Earth-mass planet could be confinedto the HZ for at least 1000 Myr sometime during the main-sequencelifetime. Clearly, these systems should be high on the target list forexploration for terrestrial planets. We have reached our conclusions bydetailed investigations of seven systems, which has resulted in anestimate of the distance from the giant planet within which orbitalstability is unlikely for an Earth-mass planet. This distance is givenby nRH, where RH is the Hill radius of the giantplanet and n is a multiplier that depends on the giant's orbitaleccentricity and on whether the Earth-mass planet is interior orexterior to the giant planet. We have estimated n for each of the sevensystems by launching Earth-mass planets in various orbits and followingtheir fate with a hybrid orbital integrator. We have then evaluated thehabitability of the other exoplanetary systems using nRHderived from the giant's orbital eccentricity without carrying outtime-consuming orbital integrations. A stellar evolution model has beenused to obtain the HZs throughout the main-sequence lifetime.
| Testing Blend Scenarios for Extrasolar Transiting Planet Candidates. II. OGLE-TR-56
We reexamine the photometric and spectroscopic evidence available forthe star OGLE-TR-56, recently discovered to harbor a giant planetpresenting transits and orbiting with a period of 1.21 days. Weinvestigate the possibility that the observational signatures reportedmight be the result of ``blending'' with the light of an eclipsingbinary along the same line of sight. Using techniques developed earlierwe perform fits to the light curve under a variety of blendconfigurations, subject to all observational constraints, and we inferfurther properties of these possible blends. We then carry out realisticend-to-end simulations based on those properties in order to quantifythe spectral line asymmetries and radial velocity variations expectedfrom such scenarios. We confront these calculations with theobservations. The results from these models are clearly inconsistentwith the measured radial velocity and bisector span variations, rulingout blends and confirming the planetary nature of the companion. Theexample of OGLE-TR-56 serves to illustrate the sort of tests that canand should be performed on transiting planet candidates to eliminate thepossibility of ``false positives'' and, in particular, line-of-sightcontamination from eclipsing binaries.
| Jumping Jupiters in Binary Star Systems
We investigate the outcomes of the dynamical interaction of Jupiter-massplanets orbiting the central star in a binary system. These systems areunstable and lead to the hyperbolic ejection of one or more planets,while the surviving bodies are inserted in inner eccentric orbits. Thegravitational perturbations of the companion star, set at anintermediate distance (50 AU) and typically on an eccentric orbit,influence both the development of instability and the outcome of thesubsequent chaotic evolution. We compute the statistical properties ofthe resulting planetary systems when they reach a stable configuration.The binary eccentricity and the number of initial planets (two or three)are strong predictors of the final configuration of the planetarysystem. Cases of apsidal resonance between two final planets, Kozairesonance between a single surviving planet and the companion star, andretrograde orbits with respect to the binary orbit are naturallyproduced.
| Binarity, activity and metallicity among late-type stars. I. Methodology and application to HD 27536 and HD 216803
We present the first in a series of papers that attempt to investigatethe relation between binarity, magnetic activity, and chemical surfaceabundances of cool stars. In the current paper, we lay out and test twoabundance analysis methods and apply them to two well-known, active,single stars, HD 27536 (G8IV-III) and HD216803 (K5V), presenting photospheric fundamental parametersand abundances of Li, Al, Ca, Si, Sc, Ti, V, Cr, Fe, Co and Ni. Theabundances from the two methods agree within the errors for all elementsexcept calcium in HD 216803, which means that either method yields thesame fundamental model parameters and the same abundances. Activity isdescribed by the radiative loss in the Ca ii H and K lines with respectto the bolometric luminosity, through the activity index R_HK. Binarityis established by very precise radial velocity (RV) measurements usingHARPS spectra. The spectral line bisectors are examined for correlationsbetween RV and bisector shape to distinguish between the effects ofstellar activity and unseen companions. We show that HD 27536 exhibit RVvariations mimicking the effect of a low-mass (m 4 M_J) companionin a relatively close (a 1 AU) orbit. The variation is stronglycorrelated with the activity, and consistent with the known photometricperiod P = 306.9 d, demonstrating a remarkable coherence between R_HKand the bisector shape, i.e. between the photosphere and thechromosphere. We discuss the complications involved in distinguishingbetween companion and activity induced RV variations.
| On the ages of exoplanet host stars
We obtained spectra, covering the CaII H and K region, for 49 exoplanethost (EH) stars, observable from the southern hemisphere. We measuredthe chromospheric activity index, R'{_HK}. We compiled previouslypublished values of this index for the observed objects as well as theremaining EH stars in an effort to better smooth temporal variations andderive a more representative value of the average chromospheric activityfor each object. We used the average index to obtain ages for the groupof EH stars. In addition we applied other methods, such as: Isochrone,lithium abundance, metallicity and transverse velocity dispersions, tocompare with the chromospheric results. The kinematic method is a lessreliable age estimator because EH stars lie red-ward of Parenago'sdiscontinuity in the transverse velocity dispersion vs dereddened B-Vdiagram. The chromospheric and isochrone techniques give median ages of5.2 and 7.4 Gyr, respectively, with a dispersion of 4 Gyr. The medianage of F and G EH stars derived by the isochrone technique is 1-2 Gyrolder than that of identical spectral type nearby stars not known to beassociated with planets. However, the dispersion in both cases is large,about 2-4 Gyr. We searched for correlations between the chromosphericand isochrone ages and L_IR/L* (the excess over the stellarluminosity) and the metallicity of the EH stars. No clear tendency isfound in the first case, whereas the metallicy dispersion seems toslightly increase with age.
| Asteroseismology of the planet-hosting star μ Arae. I. The acoustic spectrum
We present HARPS spectroscopy of μ Arae (HD 160691) performed forstudying the origin of the metallicity excess in this planet-hostingstars. The asteroseismologic campaign led to the previously reporteddiscovery of a 14 earth mass planetary companion (Santos et al. 2004b,A&A, 426, L19). The present analysis reinforces this interpretationby excluding other possible processes for explaining the observedDoppler variation and leads to the identification of up to 43 p-modeoscillations with l = 0-3, frequencies in the range 1.3-2.5 mHz andamplitudes in the range 10-40 cm s-1.
| Spectroscopic metallicities for planet-host stars: Extending the samples
We present stellar parameters and metallicities for 29 planet-hoststars, as well as for a large volume-limited sample of 53 stars notknown to be orbited by any planetary-mass companion. These stars add tothe results presented in our previous series of papers, providing twolarge and uniform samples of 119 planet-hosts and 94“single” stars with accurate stellar parameters and [Fe/H]estimates. The analysis of the results further confirms that stars withplanets are metal-rich when compared with average field dwarfs.Important biases that may compromise future studies are also discussed.Finally, we compare the metallicity distributions for singleplanet-hosts and planet-hosts in multiple stellar systems. The resultsshow that a small difference cannot be excluded, in the sense that thelatter sample is slighly overmetallic. However, more data are needed toconfirm this correlation.
| Doppler follow-up of OGLE transiting companions in the Galactic bulge
Two years ago, the OGLE-III survey (Optical Gravitational LensingExperiment) announced the detection of54short period multi-transitingobjects in the Galactic bulge (Udalski etal. [CITE],b). Some of theseobjects were considered to be potential hot Jupiters. In order todetermine the true nature of these objects and to characterize theiractual mass, we conducted a radial velocity follow-up of 18 of thesmallest transiting candidates. We describe here our procedure andreport the characterization of 8low-mass star-transiting companions,2grazing eclipsing binaries, 2triple systems, 1confirmed exoplanet(OGLE-TR-56b), 1possible exoplanet (OGLE-TR-10b), 1clear false positiveand 3unsolved cases. The variety of cases encountered in our follow-upcovers a large part of the possible scenarios occurring in the searchfor planetary transits. As a by-product our program yields precisemasses and radii of low mass stars.Based on observations collected with the UVES and FLAMES spectrographsat the VLT/UT2 Kueyen telescope (Paranal Observatory, ESO, Chile:program 70.C-0209 and 71.C-0251).
| Extrasolar Planets in Habitable Zones: Where are they?
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| Planets in multiple-star systems:properties and detections
Orbital properties of extra-solar planets are briefly recalled andcompared with equivalent features of stellar binaries. Similarities anddifferences are discussed. Among the more than 115 extra-solar planetsdiscovered to date, 19 are orbiting a component of a binary system. Wediscuss the properties of this subsample and compare them with theequivalent characteristics of planets around single stars. Differencesin the mass-period-eccentricity distributions are observed: exoplanetswith m[2]sini > 2 M [Jup] and P ≤ 40-100 days are in binaries andpresent low eccentricities. In the context of the migration scenario,these characteristics are tentatively explained in the light of recentsimulations of planet-disk interactions showing an increased accretionand migration rates of planets in case an additional perturbing closestellar companion is present in the system. Finally, differentobservational approaches to find planets in long-period spectroscopicbinaries aiming to improve the still poor available statistics arepresented. An important result is the detection of a planetary companionin the HD 41004 triple system.
| The Radiometric Bode's Law and Extrasolar Planets
We predict the radio flux densities of the extrasolar planets in thecurrent census, making use of an empirical relation-the radiometricBode's law-determined from the five ``magnetic'' planets in the solarsystem (the Earth and the four gas giants). Radio emission from theseplanets results from solar wind-powered electron currents depositingenergy in the magnetic polar regions. We find that most of the knownextrasolar planets should emit in the frequency range 10-1000 MHz and,under favorable circumstances, have typical flux densities as large as 1mJy. We also describe an initial, systematic effort to search for radioemission in low radio frequency images acquired with the Very LargeArray (VLA). The limits set by the VLA images (~300 mJy) are consistentwith, but do not provide strong constraints on, the predictions of themodel. Future radio telescopes, such as the Low Frequency Array and theSquare Kilometer Array, should be able to detect the known extrasolarplanets or place austere limits on their radio emission. Planets withmasses much lower than those in the current census will probably radiatebelow 10 MHz and will require a space-based array.
| New Data and Improved Parameters for the Extrasolar Transiting Planet OGLE-TR-56b
We report new spectroscopic observations with the Keck HIRES instrumentof the recently discovered transiting planet OGLE-TR-56b. Our radialvelocity measurements with errors of ~100 m s-1 show clearvariations that are in excellent agreement with the phasing (period andepoch) derived from the OGLE transit photometry. Careful analysis of thespectral line bisectors, along with numerical simulations of blendscenarios, supports the argument for the planetary nature of thecompanion. The new data, combined with measurements from the previousseason, allow an improved determination of the mass of the planet,Mp=(1.45+/-0.23)MJup. All available OGLEphotometry, including new measurements made during the 2003 season, havealso been analyzed to derive an improved value for the planetary radiusof Rp=(1.23+/-0.16)RJup. We discuss theimplications of these results for the theory of extrasolar planets.
| Multi-order TODCOR: Application to observations taken with the CORALIE echelle spectrograph. II. A planet in the system HD 41004
In previous works we reported the detection of a brown-dwarf companionorbiting the faint stellar component of the visual binary HD41004. This had been achieved by applying the multi-orderTwO-Dimensional CORrelation (TODCOR) algorithm to CORALIE spectra. Along-term trend of the primary component had also been detected. In thispaper we report follow-up observations that seem to unravel the natureof this long-term trend. The new measurements are consistent with thepresence of a 2.5 MJ planet in an eccentric orbit around HD 41004 A. Thus, HD 41004 is aunique hierarchical system with a brown dwarf that accompanies the faintM-component, and a planet that orbits the brighter K-component.Based on observations collected at the La Silla Observatory, ESO(Chile), with the CORALIE spectrograph at the 1.2-m Euler Swisstelescope.Table 2 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbrg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbrg.fr/cgi-bin/qcat?J/A+A/426/695
| A search for disks around exoplanet host stars
We have assembled a database which comprises optical and infrared (IR)photometry of Exoplanet Host stars (EHs), and constructed the spectralenergy distributions (SEDs) of these stars. We use several quantities toexplore the existence of excess IR emission with respect to thephotospheric level. In particular, the criteria proposed by \citet{mb}identify IR excess in 19-23% of the class V EH sources (i.e., in 6-7 outof 31). Several searches for Vega-like systems have yielded a similarfraction of objects with IR excess emission among main sequence stars.This excess emission is likely due to the presence of dust incircumstellar disks. We compare the optical polarization properties ofthe EHs, Vega-like candidate objects and pre-main sequence stars. Whilethe median polarizations of the EHs and Vega-like candidate objects arevery similar, both groups have significant lower median opticalpolarization values than T Tauri and Herbig AeBe stars.
| 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
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| Takýmyýldýz: | Ressam |
| Sað Açýklýk: | 05h59m49.65s |
| Yükselim: | -48°14'22.9" |
| Görünürdeki Parlaklýk: | 8.628 |
| Uzaklýk: | 43.029 parsek |
| özdevim Sað Açýklýk: | -42.2 |
| özdevim Yükselim: | 66.5 |
| B-T magnitude: | 9.701 |
| V-T magnitude: | 8.717 |
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