Ýçindekiler
Görüntüler
Resim Yükleyin
DSS Images Other Images
Ýlgili Makaleler
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
| Formation and Evolution of Planetary Systems: Properties of Debris Dust Around Solar-Type Stars
We present Spitzer photometric (IRAC and MIPS) and spectroscopic (IRSlow resolution) observations for 314 stars in the Formation andEvolution of Planetary Systems Legacy program. These data are used toinvestigate the properties and evolution of circumstellar dust aroundsolar-type stars spanning ages from approximately 3 Myr-3 Gyr.We identify 46 sources that exhibit excess infrared emission above thestellar photosphere at 24 μm, and 21 sources with excesses at 70μm. Five sources with an infrared excess have characteristics ofoptically thick primordial disks, while the remaining sources haveproperties akin to debris systems. The fraction of systems exhibiting a24 μm excess greater than 10.2% above the photosphere is 15% for ages< 300 Myr and declines to 2.7% for older ages. The upper envelope tothe 70 μm fractional luminosity appears to decline over a similar agerange. The characteristic temperature of the debris inferred from theIRS spectra range between 60 and 180 K, with evidence for the presenceof cooler dust to account for the strength of the 70 μm excessemission. No strong correlation is found between dust temperature andstellar age. Comparison of the observational data with disk modelscontaining a power-law distribution of silicate grains suggests that thetypical inner-disk radius is gsim 10 AU. Although the interpretation isnot unique, the lack of excess emission shortward of 16 μm and therelatively flat distribution of the 24 μm excess for ages lsim 300Myr is consistent with steady-state collisional models.
| The Palomar/Keck Adaptive Optics Survey of Young Solar Analogs: Evidence for a Universal Companion Mass Function
We present results from an adaptive optics survey for substellar andstellar companions to Sun-like stars. The survey targeted 266 F5-K5stars in the 3 Myr-3 Gyr age range with distances of 10-190 pc.Results from the survey include the discovery of two brown dwarfcompanions (HD 49197B and HD 203030B), 24 new stellar binaries, and atriple system. We infer that the frequency of 0.012-0.072Msun brown dwarfs in 28-1590 AU orbits around young solaranalogs is 3.2+3.1 -2.7% (2σ limits).The result demonstrates that the deficiency of substellar companions atwide orbital separations from Sun-like stars is less pronounced than inthe radial velocity "brown dwarf desert." We infer that the massdistribution of companions in 28-1590 AU orbits around solar-mass starsfollows a continuous dN/dM 2 vprop M -0.42 relation over the 0.01-1.0 M sun secondary massrange. While this functional form is similar to that for isolatedobjects less than 0.1 M sun, over the entire 0.01-1.0 Msun range, the mass functions of companions and of isolatedobjects differ significantly. Based on this conclusion and on similarresults from other direct imaging and radial velocity companion surveysin the literature, we argue that the companion mass function follows thesame universal form over the entire range between 0 and 1590 AU inorbital semimajor axis and ≈ 0.01-20 M sun in companionmass. In this context, the relative dearth of substellar versus stellarsecondaries at all orbital separations arises naturally from theinferred form of the companion mass function.
| The Formation and Evolution of Planetary Systems: Description of the Spitzer Legacy Science Database
We present the science database produced by the Formation and Evolutionof Planetary Systems (FEPS) Spitzer Legacy program. Data reduction andvalidation procedures for the IRAC, MIPS, and IRS instruments aredescribed in detail. We also derive stellar properties for the FEPSsample from available broadband photometry and spectral types, andpresent an algorithm to normalize Kurucz synthetic spectra to opticaland near-infrared photometry. The final FEPS data products include IRACand MIPS photometry for each star in the FEPS sample and calibrated IRSspectra.
| High-Dispersion Optical Spectra of Nearby Stars Younger Than the Sun
We present high-dispersion (R~16,000) optical (3900-8700 Å)spectra of 390 stars obtained with the Palomar 60 inch telescope. Themajority of stars observed are part of the Spitzer Legacy ScienceProgram ``The Formation and Evolution of Planetary Systems.'' Throughdetailed analysis we determine stellar properties for this sample,including radial and rotational velocities, Li I λ6708 andHα equivalent widths, the chromospheric activity indexR'HK, and temperature- and gravity-sensitive lineratios. Several spectroscopic binaries are also identified. From ourtabulations, we illustrate basic age- and rotation-related correlationsamong measured indices. One novel result is that Ca II chromosphericemission appears to saturate at vsini values above ~30 kms-1, similar to the well-established saturation of X-raysthat originate in the spatially separate coronal region.
| Structure and Evolution of Nearby Stars with Planets. II. Physical Properties of ~1000 Cool Stars from the SPOCS Catalog
We derive detailed theoretical models for 1074 nearby stars from theSPOCS (Spectroscopic Properties of Cool Stars) Catalog. The Californiaand Carnegie Planet Search has obtained high-quality (R~=70,000-90,000,S/N~=300-500) echelle spectra of over 1000 nearby stars taken with theHamilton spectrograph at Lick Observatory, the HIRES spectrograph atKeck, and UCLES at the Anglo Australian Observatory. A uniform analysisof the high-resolution spectra has yielded precise stellar parameters(Teff, logg, vsini, [M/H], and individual elementalabundances for Fe, Ni, Si, Na, and Ti), enabling systematic erroranalyses and accurate theoretical stellar modeling. We have created alarge database of theoretical stellar evolution tracks using the YaleStellar Evolution Code (YREC) to match the observed parameters of theSPOCS stars. Our very dense grids of evolutionary tracks eliminate theneed for interpolation between stellar evolutionary tracks and allowprecise determinations of physical stellar parameters (mass, age,radius, size and mass of the convective zone, surface gravity, etc.).Combining our stellar models with the observed stellar atmosphericparameters and uncertainties, we compute the likelihood for each set ofstellar model parameters separated by uniform time steps along thestellar evolutionary tracks. The computed likelihoods are used for aBayesian analysis to derive posterior probability distribution functionsfor the physical stellar parameters of interest. We provide a catalog ofphysical parameters for 1074 stars that are based on a uniform set ofhigh-quality spectral observations, a uniform spectral reductionprocedure, and a uniform set of stellar evolutionary models. We explorethis catalog for various possible correlations between stellar andplanetary properties, which may help constrain the formation anddynamical histories of other planetary systems.
| The Formation and Evolution of Planetary Systems: Placing Our Solar System in Context with Spitzer
We provide an overview of the Spitzer Legacy Program, Formation andEvolution of Planetary Systems, that was proposed in 2000, begun in2001, and executed aboard the Spitzer Space Telescope between 2003 and2006. This program exploits the sensitivity of Spitzer to carry outmid-infrared spectrophotometric observations of solar-type stars. With asample of ~328 stars ranging in age from ~3 Myr to ~3 Gyr, we trace theevolution of circumstellar gas and dust from primordial planet-buildingstages in young circumstellar disks through to older collisionallygenerated debris disks. When completed, our program will help define thetimescales over which terrestrial and gas giant planets are built,constrain the frequency of planetesimal collisions as a function oftime, and establish the diversity of mature planetary architectures. Inaddition to the observational program, we have coordinated a concomitanttheoretical effort aimed at understanding the dynamics of circumstellardust with and without the effects of embedded planets, dust spectralenergy distributions, and atomic and molecular gas line emission.Together with the observations, these efforts will provide anastronomical context for understanding whether our solar system-and itshabitable planet-is a common or a rare circumstance. Additionalinformation about the FEPS project can be found on the team Web site.
| 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.
| Tertiary companions to close spectroscopic binaries
We have surveyed a sample of 165 solar-type spectroscopic binaries (SB)with periods from 1 to 30 days for higher-order multiplicity. Asubsample of 62 targets were observed with the NACO adaptive opticssystem and 13 new physical tertiary companions were detected. Anadditional 12 new wide companions (5 still tentative) were found usingthe 2MASS all-sky survey. The binaries belong to 161 stellar systems; ofthese 64 are triple, 11 quadruple and 7 quintuple. After correction forincompleteness, the fraction of SBs with additional companions is foundto be 63% ± 5%. We find that this fraction is a strong functionof the SB period P, reaching 96% for P<3d and dropping to34% for P>12^d. Period distributions of SBs with and withouttertiaries are significantly different, but their mass ratiodistributions are identical. The statistical data on the multiplicity ofclose SBs presented in this paper indicates that the periods and massratios of SBs were established very early, but the periods of SB systemswith triples were further shortened by angular momentum exchange withcompanions.
| 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.
| Evolution of Cold Circumstellar Dust around Solar-type Stars
We present submillimeter (Caltech Submillimeter Observatory 350 μm)and millimeter (Swedish-ESO Submillimetre Telescope [SEST] 1.2 mm, OwensValley Radio Observatory [OVRO] 3 mm) photometry for 127 solar-typestars from the Formation and Evolution of Planetary Systems SpitzerLegacy program that have masses between ~0.5 and 2.0 Msolarand ages from ~3 Myr to 3 Gyr. Continuum emission was detected towardfour stars with a signal-to-noise ratio>=3: the classical T Tauristars RX J1842.9-3532, RX J1852.3-3700, and PDS 66 with SEST, and thedebris-disk system HD 107146 with OVRO. RX J1842.9-3532 and RXJ1852.3-3700 are located in projection near the R CrA molecular cloud,with estimated ages of ~10 Myr (Neuhäuser et al.), whereas PDS 66is a probable member of the ~20 Myr old Lower Centaurus-Crux subgroup ofthe Scorpius-Centaurus OB association (Mamajek et al.). The continuumemission toward these three sources is unresolved at the 24" SESTresolution and likely originates from circumstellar accretion disks,each with estimated dust masses of ~5×10-5Msolar. Analysis of the visibility data toward HD 107146(age~80-200 Myr) indicates that the 3 mm continuum emission is centeredon the star within the astrometric uncertainties and resolved with aGaussian-fit FWHM size of (6.5"+/-1.4")×(4.2"+/-1.3"), or185AU×120 AU. The results from our continuum survey are combinedwith published observations to quantify the evolution of dust mass withtime by comparing the mass distributions for samples with differentstellar ages. The frequency distribution of circumstellar dust massesaround solar-type stars in the Taurus molecular cloud (age~2 Myr) isdistinguished from that around 3-10 Myr and 10-30 Myr old stars at asignificance level of ~1.5 and ~3 σ, respectively. These resultssuggest a decrease in the mass of dust contained in small dust grainsand/or changes in the grain properties by stellar ages of 10-30 Myr,consistent with previous conclusions. Further observations are needed todetermine if the evolution in the amount of cold dust occurs on evenshorter timescales.
| 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 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
| Nearby young stars
We present the results of an extensive all-sky survey of nearby stars ofspectral type F8 or later in a systematic search of young (zero-age mainsequence) objects. Our sample has been derived by cross-correlating theROSAT All-Sky Survey and the TYCHO catalogue, yielding a total of 754candidates distributed more or less randomly over the sky. Follow-upspectroscopy of these candidate objects has been performed on 748 ofthem. We have discovered a tight kinematic group of ten stars withextremely high lithium equivalent widths that are presumably youngerthan the Pleiades, but again distributed rather uniformly over the sky.Furthermore, about 43 per cent of our candidates have detectable levelsof lithium, thus indicating that these are relatively young objects withages not significantly above the Pleiades age.Based on observations collected at the European Southern Observatory,Chile (ESO No. 62.I-0650, 66.D-0159(A), 67.D-0236(A)).
| 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.
| A Multiplicity Survey of Chromospherically Active and Inactive Stars
Surveys of three samples of solar-type stars, segregated bychromospheric emission level, were made to determine their multiplicityfractions and to investigate the evolution of multiplicity with age. Intotal, 245 stars were searched for companions with DeltaV <= 3.0 andseparations of 0.035" to 1.08" using optical speckle interferometry. Byincorporating the visual micrometer survey for duplicity of theLamontHussey Observatory, the angular coverage was extended to 5.0" withno change in the DeltaV limit. This magnitude difference allows massratios of 0.63 and larger to be detected throughout a search region of2-127 AU for the stars observed. The 84 primaries observed in thechromospherically active sample are presumably part of a youngpopulation and are found to have a multiplicity fraction of 17.9% +/-4.6%. The sample of 118 inactive, presumably older, primaries wereselected and observed using identical methods and are found to have amultiplicity fraction of only 8.5% +/- 2.7%. Given the known linkbetween chromospheric activity and age, these results tentatively implya decreasing stellar multiplicity fraction from 1 to 4 Gyr, theapproximate ages of the two samples. Finally, only two of the 14 veryactive primaries observed were found to have a companion meeting thesurvey detection parameters. In this case, many of the systems areeither very young, or close, RS CVn type multiples that are unresolvableusing the techniques employed here.
| Metallicity effects on the chromospheric activity-age relation for late-type dwarfs
We show that there is a relationship between the age excess, defined asthe difference between the stellar isochrone and chromospheric ages, andthe metallicity as measured by the index [Fe/H] for late-type dwarfs.The chromospheric age tends to be lower than the isochrone age formetal-poor stars, and the opposite occurs for metal-rich objects. Wesuggest that this could be an effect of neglecting the metallicitydependence of the calibrated chromospheric emission-age relation. Wepropose a correction to account for this dependence. We also investigatethe metallicity distributions of these stars, and show that there aredistinct trends according to the chromospheric activity level. Inactivestars have a metallicity distribution which resembles the metallicitydistribution of solar neighbourhood stars, while active stars appear tobe concentrated in an activity strip on the logR'_HKx[Fe/H] diagram. Weprovide some explanations for these trends, and show that thechromospheric emission-age relation probably has different slopes on thetwo sides of the Vaughan-Preston gap.
| A Survey of Ca II H and K Chromospheric Emission in Southern Solar-Type Stars
More than 800 southern stars within 50 pc have been observed forchromospheric emission in the cores of the Ca II H and K lines. Most ofthe sample targets were chosen to be G dwarfs on the basis of colors andspectral types. The bimodal distribution in stellar activity first notedin a sample of northern stars by Vaughan and Preston in 1980 isconfirmed, and the percentage of active stars, about 30%, is remarkablyconsistent between the northern and southern surveys. This is especiallycompelling given that we have used an entirely different instrumentalsetup and stellar sample than used in the previous study. Comparisons tothe Sun, a relatively inactive star, show that most nearby solar-typestars have a similar activity level, and presumably a similar age. Weidentify two additional subsamples of stars -- a very active group, anda very inactive group. The very active group may be made up of youngstars near the Sun, accounting for only a few percent of the sample, andappears to be less than ~0.1 Gyr old. Included in this high-activitytail of the distribution, however, is a subset of very close binaries ofthe RS CVn or W UMa types. The remaining members of this population maybe undetected close binaries or very young single stars. The veryinactive group of stars, contributting ~5%--10% to the total sample, maybe those caught in a Maunder Minimum type phase. If the observations ofthe survey stars are considered to be a sequence of snapshots of the Sunduring its life, we might expect that the Sun will spend about 10% ofthe remainder of its main sequence life in a Maunder Minimum phase.
| SANTIAGO 91, a right ascension catalogue of 3387 stars (equinox J2000).
The positions in right ascension of 3387 stars belonging to the Santiago67 Catalogue, observed with the Repsold Meridian Circle at Cerro Calan,National Astronomical Observatory, during the period 1989 to 1994, aregiven. The average mean square error of a position, for the wholeCatalogue, is +/-0.009 s. The mean epoch of the catalogue is 1991.84.
| Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
|
Yeni bir Makale Öner
Ýlgili Baðlantýlar
Yeni Bir Baðlantý Öner
sonraki gruplarýn üyesi:
|
Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Su Yilani |
| Sað Açýklýk: | 14h58m30.52s |
| Yükselim: | -28°42'34.3" |
| Görünürdeki Parlaklýk: | 7.676 |
| Uzaklýk: | 48.996 parsek |
| özdevim Sað Açýklýk: | -100.5 |
| özdevim Yükselim: | -92.9 |
| B-T magnitude: | 8.32 |
| V-T magnitude: | 7.73 |
Kataloglar ve belirtme:
|
