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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 We include fivepreviously unpublished exoplanets orbiting the stars HD 11964, HD 66428,HD 99109, HD 107148, and HD 164922.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.
| 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.
| Galactic model parameters for field giants separated from field dwarfs by their 2MASS and V apparent magnitudes
We present a method which separates field dwarfs and field giants bytheir 2MASS and V apparent magnitudes. This method is based onspectroscopically selected standards and is hence reliable. We appliedit to stars in two fields, SA 54 and SA 82, and we estimated a full setof Galactic model parameters for giants including their total localspace density. Our results are in agreement with the ones given in therecent literature.
| Dwarfs in the Local Region
We present lithium, carbon, and oxygen abundance data for a sample ofnearby dwarfs-a total of 216 stars-including samples within 15 pc of theSun, as well as a sample of local close giant planet (CGP) hosts (55stars) and comparison stars. The spectroscopic data for this work have aresolution of R~60,000, a signal-to-noise ratio >150, and spectralcoverage from 475 to 685 nm. We have redetermined parameters and derivedadditional abundances (Z>10) for the CGP host and comparison samples.From our abundances for elements with Z>6 we determine the meanabundance of all elements in the CGP hosts to range from 0.1 to 0.2 dexhigher than nonhosts. However, when relative abundances ([x/Fe]) areconsidered we detect no differences in the samples. We find nodifference in the lithium contents of the hosts versus the nonhosts. Theplanet hosts appear to be the metal-rich extension of local regionabundances, and overall trends in the abundances are dominated byGalactic chemical evolution. A consideration of the kinematics of thesample shows that the planet hosts are spread through velocity space;they are not exclusively stars of the thin disk.
| 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.
| Frequency of Hot Jupiters and Very Hot Jupiters from the OGLE-III Transit Surveys toward the Galactic Bulge and Carina
We derive the frequencies of hot Jupiters (HJs) with 3-5 day periods andvery hot Jupiters (VHJs) with 1-3 day periods by comparing the planetsactually detected in the OGLE-III survey with those predicted by ourmodels. The models are constructed following Gould and Morgan (2003) bypopulating the line of sight with stars drawn from the HipparcosCatalogue. Using these, we demonstrate that the number of stars withsensitivity to HJs and VHJs is only 5-16% of those in the OGLE-IIIfields satisfying the spectroscopic-follow-up limit of V_max < 17.5mag. Hence, the frequencies we derive are much higher than a naiveestimate would indicate. We find that at 90% confidence the fraction ofstars with planets in the two period ranges is (1/320)(1^+1.37_-0.59)for HJs and (1/710)(1^+1.10_-0.54) for VHJs. The HJ rate isstatistically indistinguishable from that found in radial velocity (RV)studies. However, we note that magnitude-limited RV samples are heavilybiased toward metal-rich (hence, planet-bearing) stars, while transitsurveys are not, and therefore we expect that more sensitive transitsurveys should find a deficit of HJs as compared to RV surveys. Thedetection of three transiting VHJs, all with periods less than 2 days,is marginally consistent with the complete absence of such detections inRV surveys. The planets detected are consistent with being uniformlydistributed between 1.00 and 1.25 Jovian radii, but there are too few inthe sample to map this distribution in detail.
| Oxygen abundances in planet-harbouring stars. Comparison of different abundance indicators
We present a detailed and uniform study of oxygen abundances in 155solar type stars, 96 of which are planet hosts and 59 of which form partof a volume-limited comparison sample with no known planets. EWmeasurements were carried out for the [O I] 6300 Å line and the OI triplet, and spectral synthesis was performed for several OH lines.NLTE corrections were calculated and applied to the LTE abundanceresults derived from the O I 7771-5 Å triplet. Abundances from [OI], the O I triplet and near-UV OH were obtained in 103, 87 and 77dwarfs, respectively. We present the first detailed and uniformcomparison of these three oxygen indicators in a large sample ofsolar-type stars. There is good agreement between the [O/H] ratios fromforbidden and OH lines, while the NLTE triplet shows a systematicallylower abundance. We found that discrepancies between OH, [O I] and the OI triplet do not exceed 0.2 dex in most cases. We have studied abundancetrends in planet host and comparison sample stars, and no obviousanomalies related to the presence of planets have been detected. Allthree indicators show that, on average, [O/Fe] decreases with [Fe/H] inthe metallicity range -0.8< [Fe/H] < 0.5. The planet host starspresent an average oxygen overabundance of 0.1-0.2 dex with respect tothe comparison sample.
| 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.
| Spectroscopic Properties of Cool Stars (SPOCS). I. 1040 F, G, and K Dwarfs from Keck, Lick, and AAT Planet Search Programs
We present a uniform catalog of stellar properties for 1040 nearby F, G,and K stars that have been observed by the Keck, Lick, and AAT planetsearch programs. Fitting observed echelle spectra with synthetic spectrayielded effective temperature, surface gravity, metallicity, projectedrotational velocity, and abundances of the elements Na, Si, Ti, Fe, andNi, for every star in the catalog. Combining V-band photometry andHipparcos parallaxes with a bolometric correction based on thespectroscopic results yielded stellar luminosity, radius, and mass.Interpolating Yonsei-Yale isochrones to the luminosity, effectivetemperature, metallicity, and α-element enhancement of each staryielded a theoretical mass, radius, gravity, and age range for moststars in the catalog. Automated tools provide uniform results and makeanalysis of such a large sample practical. Our analysis method differsfrom traditional abundance analyses in that we fit the observed spectrumdirectly, rather than trying to match equivalent widths, and wedetermine effective temperature and surface gravity from the spectrumitself, rather than adopting values based on measured photometry orparallax. As part of our analysis, we determined a new relationshipbetween macroturbulence and effective temperature on the main sequence.Detailed error analysis revealed small systematic offsets with respectto the Sun and spurious abundance trends as a function of effectivetemperature that would be inobvious in smaller samples. We attempted toremove these errors by applying empirical corrections, achieving aprecision per spectrum of 44 K in effective temperature, 0.03 dex inmetallicity, 0.06 dex in the logarithm of gravity, and 0.5 kms-1 in projected rotational velocity. Comparisons withprevious studies show only small discrepancies. Our spectroscopicallydetermined masses have a median fractional precision of 15%, but theyare systematically 10% higher than masses obtained by interpolatingisochrones. Our spectroscopic radii have a median fractional precisionof 3%. Our ages from isochrones have a precision that variesdramatically with location in the Hertzsprung-Russell diagram. We planto extend the catalog by applying our automated analysis technique toother large stellar samples.
| 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.
| Radial Velocity Detectability of Low-Mass Extrasolar Planets in Close Orbits
Detection of Jupiter-mass companions to nearby solar-type stars withprecise radial velocity measurements is now routine, and Doppler surveysare moving toward lower velocity amplitudes. The detection of severalNeptune-mass planets with orbital periods of less than a week has beenreported. The drive toward the search for close-in, Earth-mass planetsis on the agenda. Successful detection or meaningful upper limits willplace important constraints on the process of planet formation. In thispaper, we quantify the statistics of detection of low-mass planets inclose orbits, showing how the detection threshold depends on the numberand timing of the observations. In particular, we consider the case of alow-mass planet close to but not on the 2:1 mean motion resonance with ahot Jupiter. This scenario is a likely product of the core-accretionhypothesis for planet formation coupled with migration of Jupiters inthe protoplanetary disk. It is also advantageous for detection becausethe orbital period is well constrained. We show that the minimumdetectable mass is ~4 M⊕(N/20)-1/2(σ/ms-1)(P/days)1/3(M*/Msolar)2/3for N>=20, where N is the number of observations, P is the orbitalperiod, σ is the quadrature sum of Doppler velocity measurementerrors and stellar jitter, and M* is the stellar mass.Detection of few Earth-mass rocky cores will require ~1 m s-1velocity precision and, most important, a better understanding ofstellar radial velocity ``jitter.''
| 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.
| Search for nearby stars among proper motion stars selected by optical-to-infrared photometry. III. Spectroscopic distances of 322 NLTT stars
Distance estimates based on low-resolution spectroscopy and Two MicronAll Sky Survey (2MASS) J magnitudes are presented for a large sample of322 nearby candidates from Luyten's NLTT catalogue. Mainly relativelybright (typically 7 < Ks < 11) and red high propermotion stars have been selected according to their 2MASS magnitudes andoptical-to-infrared colours (+1 < R-Ks < +7). Some LHSstars previously lacking spectroscopy have also been included. We haveclassified the majority of the objects as early-M dwarfs (M 2-M 5). Morethan 70% of our targets turned out to lie within the 25 pc horizon ofthe catalogue of nearby stars, with 50 objects placed within 15 pc and 8objects being closer than 10 pc. Three objects in the 10 pc sample haveno previously published spectral type: LP 876-10 (M 4), LP 870-65 (M4.5), and LP 869-26 (M 5). A large fraction of the objects in our sample(57%) have independent distance estimates, mainly by the recent effortsof Reid and collaborators. Our distance determinations are generally ingood agreement with theirs. 11 rather distant (d > 100 pc) objectshave also been identified, including a probable halo, but relatively hot(T_eff13 000 K) white dwarf (LHS 1200) and 10 red dwarfs withextremely large tangential velocities (250 < vt < 1150km s-1). Altogether, there are 11 red dwarfs (including onewithin 70 pc) with tangential velocities larger than about 250 kms-1. All these objects are suspected to be in fact subdwarfs,if so, their distances would be only about half of our originalestimates. The three most extreme objects in that respect are the K andearly M dwarfs LP 323-168, LHS 5343 and LP 552-21 with correcteddistances between 180 pc and 400 pc and resulting tangential velocitiesstill larger than about 400 km 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.
| Stellar wind regimes of close-in extrasolar planets
Close-in extrasolar planets of Sun-like stars are exposed to stellarwind conditions that differ considerably from those for planets in thesolar system. Unfortunately, these stellar winds belong to the stillunknown parameters of these planetary systems. On the other hand, theyplay a crucial role in a number of star-planet interaction processesthat may lead to observable radiation events. In order to lay afoundation for the investigation of such interaction processes, weestimate stellar wind parameters on the basis of the solar wind model byWeber & Davis and study the implications of the stellar magneticfields. Our results suggest that in contrast to the solar systemplanets, some close-in extrasolar planets may be obstacles in asub-Alfvénic stellar wind flow. In this case, the stellar windmagnetic pressure is comparable to or even larger than the dynamic flowpressure. We discuss possible consequences of these findings for thewind-exoplanet interactions. Further, we derive upper limit estimatesfor the energies such stellar winds can deposit in the exoplanetarymagnetospheres. We finally discuss the implications thesub-Alfvénic environment may have on the star-planet interaction.
| On the possible correlation between the orbital periods of extrasolar planets and the metallicity of the host stars
We investigate a possible correlation between the orbital periods P ofthe extrasolar planet sample and the metallicity [Fe/H] of their parentstars. Close-in planets, on orbits of a few days, are more likely to befound around metal-rich stars. Simulations show that a weak correlationis present. This correlation becomes stronger when only single starswith one detected planet are considered. We discuss several potentialsources of bias that might mimic the correlation, and find that they canbe ruled out, but not with high significance. If real, the absence ofvery short-period planets around the stellar sample with [Fe/H] < 0.0can be interpreted as evidence of a metallicity dependence of themigration rates of giant planets during formation in the protoplanetarydisc. The observed P-[Fe/H] correlation can be falsified or confirmed byconducting spectroscopic or astrometric surveys of metal-poor stars([Fe/H] < -0.5) in the field.
| Obliquity variations of terrestrial planets in habitable zones
We have investigated obliquity variations of possible terrestrialplanets in habitable zones (HZs) perturbed by a giant planet(s) inextrasolar planetary systems. All the extrasolar planets so fardiscovered are inferred to be jovian-type gas giants. However,terrestrial planets could also exist in extrasolar planetary systems. Inorder for life, in particular for land-based life, to evolve and surviveon a possible terrestrial planet in an HZ, small obliquity variations ofthe planet may be required in addition to its orbital stability, becauselarge obliquity variations would cause significant climate change. It isknown that large obliquity variations are caused by spin-orbitresonances where the precession frequency of the planet's spin nearlycoincides with one of the precession frequencies of the ascending nodeof the planet's orbit. Using analytical expressions, we evaluated theobliquity variations of terrestrial planets with prograde spins in HZs.We found that the obliquity of terrestrial planets suffers largevariations when the giant planet's orbit is separated by several Hillradii from an edge of the HZ, in which the orbits of the terrestrialplanets in the HZ are marginally stable. Applying these results to theknown extrasolar planetary systems, we found that about half of thesesystems can have terrestrial planets with small obliquity variations(smaller than 10°) over their entire HZs. However, the systems withboth small obliquity variations and stable orbits in their HZs are only1/5 of known systems. Most such systems are comprised of short-periodgiant planets. If additional planets are found in the known planetarysystems, they generally tend to enhance the obliquity variations. On theother hand, if a large/close satellite exists, it significantly enhancesthe precession rate of the spin axis of a terrestrial planet and islikely to reduce the obliquity variations of the planet. Moreover, if aterrestrial planet is in a retrograde spin state, the spin-orbitresonance does not occur. Retrograde spin, or a large/close satellitemight be essential for land-based life to survive on a terrestrialplanet in an HZ.
| Chromospheric Ca II Emission in Nearby F, G, K, and M Stars
We present chromospheric Ca II H and K activity measurements, rotationperiods, and ages for ~1200 F, G, K, and M type main-sequence stars from~18,000 archival spectra taken at Keck and Lick Observatories as a partof the California and Carnegie Planet Search Project. We have calibratedour chromospheric S-values against the Mount Wilson chromosphericactivity data. From these measurements we have calculated medianactivity levels and derived R'HK, stellar ages,and rotation periods from general parameterizations for 1228 stars,~1000 of which have no previously published S-values. We also presentprecise time series of activity measurements for these stars.Based on observations obtained at Lick Observatory, which is operated bythe University of California, and on observations obtained at the W. M.Keck Observatory, which is operated jointly by the University ofCalifornia and the California Institute of Technology. The KeckObservatory was made possible by the generous financial support of theW. M. Keck Foundation.
| The Indo-US Library of Coudé Feed Stellar Spectra
We have obtained spectra for 1273 stars using the 0.9 m coudéfeed telescope at Kitt Peak National Observatory. This telescope feedsthe coudé spectrograph of the 2.1 m telescope. The spectra havebeen obtained with the no. 5 camera of the coudé spectrograph anda Loral 3K×1K CCD. Two gratings have been used to provide spectralcoverage from 3460 to 9464 Å, at a resolution of ~1 Å FWHMand at an original dispersion of 0.44 Å pixel-1. For885 stars we have complete spectra over the entire 3460 to 9464 Åwavelength region (neglecting small gaps of less than 50 Å), andpartial spectral coverage for the remaining stars. The 1273 stars havebeen selected to provide broad coverage of the atmospheric parametersTeff, logg, and [Fe/H], as well as spectral type. The goal ofthe project is to provide a comprehensive library of stellar spectra foruse in the automated classification of stellar and galaxy spectra and ingalaxy population synthesis. In this paper we discuss thecharacteristics of the spectral library, viz., details of theobservations, data reduction procedures, and selection of stars. We alsopresent a few illustrations of the quality and information available inthe spectra. The first version of the complete spectral library is nowpublicly available from the National Optical Astronomy Observatory(NOAO) via ftp and http.
| 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.
| Are beryllium abundances anomalous in stars with giant planets?
In this paper we present beryllium (Be) abundances in a large sample of41 extra-solar planet host stars, and for 29 stars without any knownplanetary-mass companion, spanning a large range of effectivetemperatures. The Be abundances were derived through spectral synthesisdone in standard Local Thermodynamic Equilibrium, using spectra obtainedwith various instruments. The results seem to confirm that overall,planet-host stars have ``normal'' Be abundances, although a small, butnot significant, difference might be present. This result is discussed,and we show that this difference is probably not due to any stellar``pollution'' events. In other words, our results support the idea thatthe high-metal content of planet-host stars has, overall, a``primordial'' origin. However, we also find a small subset ofplanet-host late-F and early-G dwarfs that might have higher thanaverage Be abundances. The reason for the offset is not clear, and mightbe related either to the engulfment of planetary material, to galacticchemical evolution effects, or to stellar-mass differences for stars ofsimilar temperature.Based on observations collected with the VLT/UT2 Kueyen telescope(Paranal Observatory, ESO, Chile) using the UVES spectrograph (Observingruns 66.C-0116 A, 66.D-0284 A, and 68.C-0058 A), and with the WilliamHerschel and Nordic Optical Telescopes, operated on the island of LaPalma by the Isaac Newton Group and jointly by Denmark, Finland,Iceland, and Norway, respectively, in the Spanish Observatorio del Roquede los Muchachos of the Instituto de Astrofísica de Canarias.
| Tidal interactions of close-in extrasolar planets: The OGLE cases
Close-in extrasolar planets experience extreme tidal interactions withtheir host stars. This may lead to a reduction of the planetary radiusand a spin-up of stellar rotation. Tidal interactions have been computedfor a number of extrasolar planets in circular orbits within 0.06 AU,namely for OGLE-TR-56 b. We compare our range of the tidal dissipationvalue with two dissipation models from Sasselov (\cite{sasselov}) andconclude that our choices are equivalent to these models. However,applied to the planet OGLE-TR-56 b, we find in contrast to Sasselov(\cite{sasselov}) that this planet will spiral-in toward the host starin a few billion years. We show that the average and maximum value ofour range of dissipation are equivalent to the linear and quadraticdissipation models of Sasselov (\cite{sasselov}). Due to limitations inthe observational techniques, we do not see a possibility to distinguishbetween the two dissipation models as outlined by Sasselov(\cite{sasselov}). OGLE-TR-56 b may therefore not be well suited toserve as a test case for dissipation models. The probable existence ofOGLE-TR-3 b at 0.02 AU and the discovery of OGLE-TR-113 b at 0.023 AUand OGLE-TR-132 b at 0.03 AU may also counter Sasselovs(\cite{sasselov}) assumption of a pile-up stopping boundary at 0.04 AU.
| Beryllium anomalies in solar-type field stars
We present a study of beryllium (Be) abundances in a large sample offield solar-type dwarfs and sub-giants spanning a large range ofeffective temperatures. The Be abundances, computed using a very uniformset of stellar parameters and near-UV spectra obtained with 3 differentinstruments, are used to study the depletion of this light element. Theanalysis shows that Be is severely depleted for F stars, as expected bythe light-element depletion models. However, we also show that berylliumabundances decrease with decreasing temperature for stars cooler than6000 K, a result that cannot be explained by current theoreticalmodels including rotational mixing, but that is, at least in part,expected from the models that take into account internal wave physics.In particular, the light element abundances of the coolest and youngeststars in our sample suggest that Be, as well as lithium (Li), hasalready been burned early during their evolution. Furthermore, we findstrong evidence for the existence of a Be-gap for solar-temperaturestars. The analysis of Li and Be abundances in the sub-giants of oursample also shows the presence of one case that has still detectableamounts of Li, while Be is severely depleted. Finally, we compare thederived Be abundances with Li abundances derived using the same set ofstellar parameters. This gives us the possibility to explore thetemperatures for which the onset of Li and Be depletion occurs.Based on observations collected with the VLT/UT2 Kueyen telescope(Paranal Observatory, ESO, Chile) using the UVES spectrograph (Observingruns 66.C-0116 A, 66.D-0284 A, and 68.C-0058 A), and with the WilliamHerschel and Nordic Optical Telescopes, operated at the island of LaPalma by the Isaac Newton Group and jointly by Denmark, Finland,Iceland, and Norway, respectively, in the Spanish Observatorio del Roquede los Muchachos of the Instituto de Astrofísica de Canarias.
| Spectroscopic [Fe/H] for 98 extra-solar planet-host stars. Exploring the probability of planet formation
We present stellar parameters and metallicities, obtained from adetailed spectroscopic analysis, for a large sample of 98 stars known tobe orbited by planetary mass companions (almost all known targets), aswell as for a volume-limited sample of 41 stars not known to host anyplanet. For most of the stars the stellar parameters are revisedversions of the ones presented in our previous work. However, we alsopresent parameters for 18 stars with planets not previously published,and a compilation of stellar parameters for the remaining 4 planet-hostsfor which we could not obtain a spectrum. A comparison of our stellarparameters with values of Teff, log g, and [Fe/H] availablein the literature shows a remarkable agreement. In particular, ourspectroscopic log g values are now very close to trigonometric log gestimates based on Hipparcos parallaxes. The derived [Fe/H] values arethen used to confirm the previously known result that planets are moreprevalent around metal-rich stars. Furthermore, we confirm that thefrequency of planets is a strongly rising function of the stellarmetallicity, at least for stars with [Fe/H] > 0. While only about 3%of the solar metallicity stars in the CORALIE planet search sample werefound to be orbited by a planet, this number increases to more than 25%for stars with [Fe/H] above +0.3. Curiously, our results also suggestthat these percentages might remain relatively constant for values of[Fe/H] lower than about solar, increasing then linearly with the massfraction of heavy elements. These results are discussed in the contextof the theories of planetary formation.Based on observations collected at the La Silla Observatory, ESO(Chile), with the CORALIE spectrograph at the 1.2-m Euler Swisstelescope and the FEROS spectrograph at the 1.52-m and 2.2-m ESOtelescopes, with the VLT/UT2 Kueyen telescope (Paranal Observatory, ESO,Chile) using the UVES spectrograph (Observing run 67.C-0206, in servicemode), with the TNG and William Herschel Telescopes, both operated atthe island of La Palma, and with the ELODIE spectrograph at the 1.93-mtelescope at the Observatoire de Haute Provence.
| Colloquium: Stars, planets, and metals
The discovery in 1995 of the first planet orbiting another Sun-like starstimulated renewed interest in planet formation and evolution processes.A number of trends among the properties of the planets have becomeevident in the years since. An interesting pattern began to emerge in1997stars hosting planets tend to be more metal rich (i.e., havemore abundant elements with Z>2) than the average nearby star. Other,more subtle, trends are beginning to appear as the sample size continuesto grow; for example, the masses of stars hosting planets are found tocorrelate with their metallicities. The author reviews the state of ourknowledge concerning the observed trends, their possible causes, andtheir possible implications for astrophysics and astrobiology.
| Search for periodicities in distribution of orbits of planets.
Not Available
| Dynamical Habitability of Known Extrasolar Planetary Systems
Habitability is usually defined as the requirement for a terrestrialplanet's atmosphere to sustain liquid water. This definition can becomplemented by the dynamical requirement that other planets in thesystem do not gravitationally perturb terrestrial planets outside oftheir habitable zone, the orbital region allowing the existence ofliquid water. We quantify the dynamical habitability of 85 knownextrasolar planetary systems via simulations of their orbital dynamicsin the presence of potentially habitable terrestrial planets. Whenrequiring that habitable planets remain strictly within their habitablezone at all times, the perturbing influence of giant planets extendsbeyond the traditional Hill sphere for close encounters: terrestrialplanet excursions outside of the habitable zone are also caused bysecular eccentricity variations and, in some cases, strong mean-motionresonances. Our results indicate that more than half the knownextrasolar planetary systems (mostly those with distant, eccentric giantplanets) are unlikely to harbor habitable terrestrial planets. Aboutone-fourth of the systems (mostly those with close-in giant planets),including one-third of the potential targets for the Terrestrial PlanetFinder, appear as dynamically habitable as our own solar system. Theinfluence of yet undetected giant planets in these systems couldcompromise their dynamical habitability. Some habitable terrestrialplanets in our simulations have substantial eccentricities (e>0.1),which may lead to large seasonal climate variations and thus affecttheir habitability.
| Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
We complete construction of a catalog containing improved astrometry andnew optical/infrared photometry for the vast majority of NLTT starslying in the overlap of regions covered by POSS I and by the secondincremental Two Micron All Sky Survey (2MASS) release, approximately 44%of the sky. The epoch 2000 positions are typically accurate to 130 mas,the proper motions to 5.5 mas yr-1, and the V-J colors to0.25 mag. Relative proper motions of binary components are measured to 3mas yr-1. The false-identification rate is ~1% for11<~V<~18 and substantially less at brighter magnitudes. Theseimprovements permit the construction of a reduced proper-motion diagramthat, for the first time, allows one to classify NLTT stars intomain-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We inturn use this diagram to analyze the properties of both our catalog andthe NLTT catalog on which it is based. In sharp contrast to popularbelief, we find that NLTT incompleteness in the plane is almostcompletely concentrated in MS stars, and that SDs and WDs are detectedalmost uniformly over the sky δ>-33deg. Our catalogwill therefore provide a powerful tool to probe these populationsstatistically, as well as to reliably identify individual SDs and WDs.
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Observation and Astrometry data
| Constellation: | コップ座 |
| Right ascension: | 10h58m28.78s |
| Declination: | -10°46'13.3" |
| Apparent magnitude: | 10.02 |
| Proper motion RA: | -185.5 |
| Proper motion Dec: | -5.2 |
| B-T magnitude: | 11.094 |
| V-T magnitude: | 10.109 |
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