目录
图像
上传图像
DSS Images Other Images
相关文章
The frequency of giant planets around metal-poor stars
Context. The discovery of about 700 extrasolar planets, so far, has leadto the first statistics concerning extrasolar planets. The presence ofgiant planets seems to depend on stellar metallicity and mass. Forexample, they are more frequent around metal-rich stars, with anexponential increase in planet occurrence rates with metallicity. Aims: We analyzed two samples of metal-poor stars (-2.0 ? [Fe/H] ?0.0) to see if giant planets are indeed rare around these objects.Radial velocity datasets were obtained with two different spectrographs(HARPS and HIRES). Detection limits for these data, expressed in minimumplanetary mass and period, are calculated. These produce trustworthynumbers for the planet frequency. Methods: A general Lomb-Scargle(GLS) periodogram analysis was used together with a bootstrapping methodto produce the detection limits. Planet frequencies were calculatedbased on a binomial distribution function within metallicity bins. Results: Almost all hot Jupiters and most giant planets should havebeen found in these data. Hot Jupiters around metal-poor stars have afrequency lower than 1.0% at one sigma. Giant planets with periods up to1800 days, however, have a higher frequency of fp =2.63-0.8+2.5%. Taking into account the differentmetallicities of the stars, we show that giant planets appear to be veryfrequent (fp = 4.48-1.38+4.04%) aroundstars with [Fe/H] > - 0.7, while they are rare around stars with[Fe/H] ? - 0.7 ( ? 2.36% at one sigma). Conclusions: Giantplanet frequency is indeed a strong function of metallicity, even in thelow-metallicity tail. However, the frequencies are most likely higherthan previously thought.The data presented herein are based on observations collected at the LaSilla Parana Observatory, ESO (Chile) with the HARPS spectrograph at the3.6-m telescope (ESO runs ID 72.C-0488, 082.C-0212, and 085.C-0063) andat the W. M. Keck Observatory that is operated as a scientificpartnership among the California Institute of Technology, the Universityof California and the National Aeronautics and Space Administration.This Observatory was made possible by the generous financial support ofthe W. M. Keck Foundation.Full Table 1 is only available at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/543/A45AppendixA is available in electronic form at http://www.aanda.org
| The PASTEL catalogue of stellar parameters
Aims: The PASTEL catalogue is an update of the [Fe/H] catalogue,published in 1997 and 2001. It is a bibliographical compilation ofstellar atmospheric parameters providing (T_eff, log g, [Fe/H])determinations obtained from the analysis of high resolution, highsignal-to-noise spectra, carried out with model atmospheres. PASTEL alsoprovides determinations of the one parameter T_eff based on variousmethods. It is aimed in the future to provide also homogenizedatmospheric parameters and elemental abundances, radial and rotationalvelocities. A web interface has been created to query the catalogue onelaborated criteria. PASTEL is also distributed through the CDS databaseand VizieR. Methods: To make it as complete as possible, the mainjournals have been surveyed, as well as the CDS database, to findrelevant publications. The catalogue is regularly updated with newdeterminations found in the literature. Results: As of Febuary2010, PASTEL includes 30151 determinations of either T_eff or (T_eff,log g, [Fe/H]) for 16 649 different stars corresponding to 865bibliographical references. Nearly 6000 stars have a determination ofthe three parameters (T_eff, log g, [Fe/H]) with a high qualityspectroscopic metallicity.The catalogue can be queried through a dedicated web interface at http://pastel.obs.u-bordeaux1.fr/.It is also available in electronic form at the Centre de DonnéesStellaires in Strasbourg (http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=B/pastel),at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/515/A111
| A Keck HIRES Doppler Search for Planets Orbiting Metal-Poor Dwarfs. II. On the Frequency of Giant Planets in the Metal-Poor Regime
We present an analysis of three years of precision radial velocity (RV)measurements of 160 metal-poor stars observed with HIRES on the Keck 1telescope. We report on variability and long-term velocity trends foreach star in our sample. We identify several long-term, low-amplitude RVvariables worthy of followup with direct imaging techniques. We placelower limits on the detectable companion mass as a function of orbitalperiod. Our survey would have detected, with a 99.5% confidence level,over 95% of all companions on low-eccentricity orbits with velocitysemiamplitude K gsim 100 m s–1, orMp sin i gsim 3.0 M J(P/yr)(1/3), fororbital periods P lsim 3 yr. None of the stars in our sampleexhibits RV variations compatible with the presence of Jovian planetswith periods shorter than the survey duration. The resulting averagefrequency of gas giants orbiting metal-poor dwarfs with–2.0lsim[Fe/H]lsim–0.6 is fp < 0.67% (at the1σ confidence level). We examine the implications of this nullresult in the context of the observed correlation between the rate ofoccurrence of giant planets and the metallicity of their main-sequencesolar-type stellar hosts. By combining our data set with the Fischer& Valenti (2005) uniform sample, we confirm that the likelihood of astar to harbor a planet more massive than Jupiter within 2 AU is asteeply rising function of the host's metallicity. However, the data forstars with –1.0lsim[Fe/H]lsim0.0 are compatible, in a statisticalsense, with a constant occurrence rate fp sime 1%. Ourresults can usefully inform theoretical studies of the process ofgiant-planet formation across two orders of magnitude in metallicity.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| 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.
| 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.
| UVBY - beta photometry of high-velocity and metal-poor stars. VI - A second catalogue, and stellar populations of the Galaxy
A second catalog of uvby-beta photometry for 553 high-velocity stars ispresented. Combining the catalogs, reliable (Fe/H) values are obtainedfor 1214 stars and reliable kinematic parameters for 1149. The totalsample contains at least three significant, distinct stellar populationswith properties very similar to those given in the literature of the oldthin disk, thick disk, and halo. The thick-disk component has mean(Fe/H) about -0.50 +/- 0.10 dex and sigma(Fe/H) about 0.25 +/- 0.03 dex,but there is evidence for a significant thick-disk contribution down to(Fe/H) about -1.4. A diagonal cut in the V(rot), (Fe/H) diagramindicates that there is not a chemical gradient in the Galactic halo.The mean V(rot), mean (Fe/H) curve for the whole sample indicates thatthe halo evolved mostly independently of the disk.
| New subdwarfs. VI - Kinematics of 1125 high-proper-motion stars and the collapse of the Galaxy
The UVW velocity components, planar eccentricities, and angular momentaof 878 high-proper-motion stars are determined using the radial-velocitydata of Fouts and Sandage (1986) and compared with chemical abundancesand photometric parallaxes from the UBV photometry of Sandage and Kowal(1986). The results are presented, along with published data on 247additional stars, in extensive tables and graphs and characterized indetail. Two approximately equal components are differentiated: alow-velocity component identified as part of the thick disk described byGilmore and Reid (1983) and a high-velocity halo component. The data arefound to support a model of Galactic collapse (with concomitant spinupand progressive chemical enrichment) which includes a rotating bulge(the thick disk) with kinematic and metallicity properties between thoseof the old thin disk and the halo.
| New subdwarfs. V - Radial velocities for 889 high-proper-motion stars measured with the Mount Wilson 100 inch reflector
New radial velocities have been obtained from 2265 measurements of 889high-proper-motion stars taken from the subdwarf candidate list of aprevious paper. The observations were made with the Mount Wilson 100 inHooker reflector coude spectrograph with a Reticon detector, giving aninternal error of a single measurement of 4.7 km/s. From 88 stars incommon with previously known subdwarfs; the external error of the datais 6.9 km/s per measurement, and the velocity system is shown to be onthe system of the Wilson General Catalog to better than 1 km/s. Of the878 stars with nonvariable velocities in the sample, 38 have radialvelocities larger than 200 km/s, of which 22 are new. There is acorrelation between radial velocity and reduced ultraviolet excess asexpected from the previously known relations between space motion andchemical composition. The Stroemberg asymmetric drift is directlyvisible in the radial velocity and the proper-motion data separately aseach is displayed as a function of galactic longitude.
| New subdwarfs. IV - UBV photometry of 1690 high-proper-motion stars
A photometric list of 1690 stars of known high proper motion is used tosearch for potential high-velocity stars of various metallicity valuesin order to find candidates for trigonometric programs on subdwarfs andto enlarge the sample with which to study the relation between stellarkinematics and metal abundance. A list of 113 stars with tangentialspace velocities of 300 km/s or greater is obtained, the highesttangential velocity relative to the sun being 630 km/s. By using thevariation of the tangential velocity with longitude and adopting thegalactic rotation at the solar circle to be 220 km/s, the rotation ofthe subdwarf system is estimated at 0 + or - 50 km/s from the transversevelocity alone, in agreement with determinations based on other methods.
| Lowell proper motions II : proper motion survey of the Northern Hemisphere with the 13-inch photographic telescope of the Lowell Observatory
Not Available
|
提交文章
相关链接
提交链接
下列团体成员
|
观测天体数据
目录:
|
