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The Solar Neighborhood. XXV. Discovery of New Proper Motion Stars with 0farcs40 yr-1 > ? >= 0farcs18 yr-1 between Declinations -47° and 00°
We present 2817 new southern proper motion systems with 0farcs40yr-1 > ? >= 0farcs18 yr-1 and declinationbetween -47° and 00°. This is a continuation of theSuperCOSMOS-RECONS (SCR) proper motion searches of the southern sky. Weuse the same photometric relations as previous searches to providedistance estimates based on the assumption that the objects are singlemain-sequence stars. We find 79 new red dwarf systems predicted to bewithin 25 pc, including a few new components of previously knownsystems. Two systems—SCR 1731-2452 at 9.5 pc and SCR 1746-3214 at9.9 pc—are anticipated to be within 10 pc. We also find 23 newwhite dwarf (WD) candidates with distance estimates of 15-66 pc, as wellas 360 new red subdwarf candidates. With this search, we complete theSCR sweep of the southern sky for stars with ? >= 0farcs18yr-1 and R 59F <= 16.5, resulting in a totalof 5042 objects in 4724 previously unreported proper motion systems.Here we provide selected comprehensive lists from our SCR proper motionsearch to date, including 152 red dwarf systems estimated to be within25 pc (9 within 10 pc), 46 WDs (10 within 25 pc), and 598 subdwarfcandidates. The results of this search suggest that there are morenearby systems to be found at fainter magnitudes and lower proper motionlimits than those probed so far.
| The HARPS search for southern extrasolar planets. XXV. Results from the metal-poor sample
Searching for extrasolar planets around stars of different metallicitymay provide strong constraints to the models of planet formation andevolution. In this paper we present the overall results of a HARPS (ahigh-precision spectrograph mostly dedicated to deriving precise radialvelocities) program to search for planets orbiting a sample of 104metal-poor stars (selected [Fe/H] below -0.5). Radial velocity timeseries of each star are presented and searched for signals using severalstatistical diagnostics. Stars with detected signals are presented,including 3 attributed to the presence of previously announced giantplanets orbiting the stars HD 171028, HD 181720, and HD 190984. Severalbinary stars and at least one case of a coherent signal caused byactivity-related phenomena are presented. One very promising new,possible giant planet orbiting the star HD 107094 is discussed, and theresults are analyzed in light of the metallicity-giant planetcorrelation. We conclude that the frequency of giant planets orbitingmetal-poor stars may be higher than previously thought, probablyreflecting the higher precision of the HARPS survey. In the metallicitydomain of our sample, we also find evidence that the frequency ofplanets is a steeply rising function of the stellar metal content, asfound for higher metallicity stars.Based on observations collected at the La Silla Parana Observatory, ESO(Chile) with the HARPS spectrograph at the 3.6-m telescope (ESO runs ID72.C-0488, 082.C-0212, and 085.C-0063).Full Tables 1 and 3 are onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/526/A112
| Spectroscopic characterization of a sample of metal-poor solar-type stars from the HARPS planet search program. Precise spectroscopic parameters and mass estimation
Stellar metallicity strongly correlates with the presence of planets andtheir properties. To check for new correlations between stars and theexistence of an orbiting planet, we determine precise stellar parametersfor a sample of metal-poor solar-type stars. This sample was observedwith the HARPS spectrograph and is part of a program to search for newextrasolar planets. The stellar parameters were determined using an LTEanalysis based on equivalent widths (EW) of iron lines and by imposingexcitation and ionization equilibrium. The ARES code was used to allowautomatic and systematic derivation of the stellar parameters. Precisestellar parameters and metallicities were obtained for 97 lowmetal-content stars. We also present the derived masses, luminosities,and new parallaxes estimations based on the derived parameters, andcompare our spectroscopic parameters with an infra-red flux methodcalibration to check the consistency of our method in metal poor stars.Both methods seems to give the same effective temperature scale. Finallywe present a new calibration for the temperature as a function of B-Vand [Fe/H]. This was obtained by adding these new metal poor stars inorder to increase the range in metallicity for the calibration. Thestandard deviation of this new calibration is ~50 K.Based on observations collected at the La Silla Parana Observatory, ESO(Chile) with the HARPS spectrograph at the 3.6-m telescope (ESO runs ID72.C-0488, 082.C-0212, and 085.C-0063).Tables 1-3 are only available inelectronic form at http://www.aanda.org
| The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics
Context: Ages, chemical compositions, velocity vectors, and Galacticorbits for stars in the solar neighbourhood are fundamental test datafor models of Galactic evolution. The Geneva-Copenhagen Survey of theSolar Neighbourhood (Nordström et al. 2004; GCS), amagnitude-complete, kinematically unbiased sample of 16 682 nearby F andG dwarfs, is the largest available sample with complete data for starswith ages spanning that of the disk. Aims: We aim to improve theaccuracy of the GCS data by implementing the recent revision of theHipparcos parallaxes. Methods: The new parallaxes yield improvedastrometric distances for 12 506 stars in the GCS. We also use theparallaxes to verify the distance calibration for uvby? photometryby Holmberg et al. (2007, A&A, 475, 519; GCS II). We add newselection criteria to exclude evolved cool stars giving unreliableresults and derive distances for 3580 stars with large parallax errorsor not observed by Hipparcos. We also check the GCS II scales of T_effand [Fe/H] and find no need for change. Results: Introducing thenew distances, we recompute MV for 16 086 stars, and U, V, W,and Galactic orbital parameters for the 13 520 stars that also haveradial-velocity measurements. We also recompute stellar ages from thePadova stellar evolution models used in GCS I-II, using the new valuesof M_V, and compare them with ages from the Yale-Yonsei andVictoria-Regina models. Finally, we compare the observed age-velocityrelation in W with three simulated disk heating scenarios to show thepotential of the data. Conclusions: With these revisions, thebasic data for the GCS stars should now be as reliable as is possiblewith existing techniques. Further improvement must await consolidationof the T_eff scale from angular diameters and fluxes, and the Gaiatrigonometric parallaxes. We discuss the conditions for improvingcomputed stellar ages from new input data, and for distinguishingdifferent disk heating scenarios from data sets of the size andprecision of the GCS.Full Table 1 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/501/941
| 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.
| 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
| 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.
| Magnitude, color and spectral type of AQL X-1 in quiescence
Direct I and V-band imaging of Aql X-1 in quiescence and during outburstmaximum shows that the true optical counterpart is the interloperlocated 0.48'' West of the previously known star. We find for the newcounterpart V = 21.6 and V-I = 2.2 in quiescence, when its contributionto the total light was 12% in V and 22% in I. Analysis of thisphotometry and of low-resolution spectra of the sum of both stars, alsotaken during quiescence, shows that the likely spectral types for thepreviously known star and the optical counterpart are late G and late K,respectively, reddened by E(B-V) = 0.5+/-0.1. Based on observationsobtained at the European Southern Observatory, La Silla, Chile
| The general catalogue of trigonometric [stellar] paralaxes
Not Available
| A large, complete, volume-limited sample of G-type dwarfs. I. Completion of Stroemgren UVBY photometry
Four-colour photometry of potential dwarf stars of types G0 to K2,selected from the Michigan Spectral Catalogues (Vol. 1-3), has beencarried out. The results are presented in a catalogue containing 4247uvby observations of 3900 stars, all south of δ = -26deg. Theoverall internal rms errors of one observation (transformed to thestandard system) of a program star in the interval 8.5 < V < 10.5are 0.0044, 0.0021, 0.0039, and 0.0059, respectively, in V, b-y, m_1_ ,and c_1_. The purpose of the catalogue, combined with earliercatalogues, is to allow selection of a large, complete, volume-limitedsample of G- and K-type dwarfs, investigate their metallicitydistribution, and compare it to predictions of various models ofgalactic chemical evolution. Future papers in this series will discussthese subjects.
| Subdwarf studies. I - UBVRI photometry of NLTT stars
UBVRI photometry is presented for a sample of 1656 southern stars,including 1211 that were previously unmeasured, drown from the NLTTproper-motion catalog. The catalog is shown to be a rich source ofsubdwarfs. The normalized ultraviolet excess delta (U - B)0.6,photometric parallax, and interstellar reddening are calculated for eachstar when possible. Photometric parallaxes are compared withtrigonometric parallaxes from the literature. It is found that theformer do not have systematic errors greater than about 25 percent. Inagreement with other studies, the bluest subdwarfs are found at B - V =0.35. The selection of the program stars on the basis of large reducedproper motions restricted subgiant contamination of the sample to about5 percent and increased the discovery fraction of halo stars relative todisk stars. The claim is made here that the sample can be used toinvestigate the abundance distribution of the halo. The sample includesstars with ultraviolet excesses characteristic of disk abundances butwith velocities up to 150 km/s. These are believed to be stars that,quite expectedly, reside in the high-velocity tail of the disk velocitydistribution.
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| Takýmyýldýz: | Sunak |
| Sað Açýklýk: | 18h03m41.44s |
| Yükselim: | -45°51'43.5" |
| Görünürdeki Parlaklýk: | 9.643 |
| özdevim Sað Açýklýk: | 48.4 |
| özdevim Yükselim: | -242.5 |
| B-T magnitude: | 10.52 |
| V-T magnitude: | 9.716 |
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