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Публикации по объекту
A 2 Micron H2 Spectral Survey of Proto-Planetary Nebulae
We measured 2.1-2.3 μm spectra for a mostly complete sample of knownproto-planetary nebulae (PPNe) at declinations north of -30°. Thisspectral range includes the H2 emission lines 1-0 S(1), 1-0S(0), 2-1 S(1), 2-1 S(2), and 3-2 S(3). We detected H2emission from 16 of the 51 objects in our survey. Twelve of these arenew detections, doubling the number of PPNe with detected H2emission. We find that H2 emission commences at a spectralclass of mid-G in PPNe with bipolar morphologies and optically thickequatorial regions; in fact, all bipolar F-G PPNe with an opticallythick equatorial region have collisionally excited H2emission. Radiative excitation becomes important in PPNe when thecentral star reaches an early B spectral type, just beforephotoionization of the nebula and the commencement of the planetarynebula (PN) phase. Almost all of the PPNe with B central stars showH2 emission, with either a purely radiative or a mixedcollisional plus radiative spectrum. Since H2 emission israre in nonbipolar PNe, the destruction of the H2 in thenonbipolars must be roughly coincident with the photoionization of thenebula. As with H2-emitting PNe, the bipolarH2-emitting PPNe are found at low Galactic latitudes.Optically thin H2-emitting nebulae are not similarlyrestricted to low latitudes. Brγ emission is detected in 15 of thesources, including all those of B spectral type.
| 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
| The Nature of Overluminous F Stars Observed in a Radial-Velocity Survey
We have conducted a radial-velocity survey of bright (V<9),overluminous, F stars within 80 pc. The criterion of overluminosity isΔMc0=Mc0-MV>=0.5,where MV is the absolute magnitude based on the Hipparcosparallax and Mc0 is the absolute magnitude fromuvby photometry. For F stars, overluminosity at a level ofΔMc0>0.15 has been argued to beindicative of the presence of a bright companion, so many of theoverluminous ``single'' F stars are expected to be, in fact, binarieswith comparably bright components. Therefore, the main goals of thesurvey have been to gain insight into the nature of overluminous F starsand to test specifically the hypothesis of the duplicity of overluminousF stars by searching for previously unrecognized binary stars amongthem. Other goals of this project included the determination, whereverpossible, of the orbits of the binaries discovered as a result of thesurvey and comparing the properties of the binaries with those of thevisually single stars with constant radial velocity. The program listcomprised 111 stars that appear in the Hipparcos catalog as single, plusseven members of multiple systems whose components have individualentries in the catalog.Of the total of 118 stars selected, the radial velocities of 77 havebeen measured with the Cambridge CORAVEL in the present survey. Amongthe remainder, six have not allowed us to determine their radialvelocities because of the weakness or lack of a ``dip'' in theirradial-velocity traces, and one was optically inaccessible to thetelescope. All the rest proved to be sufficiently well known alreadyeither as binary or as constant-radial-velocity (CRV) stars. The surveydiscovered 25 new binary systems, not counting two that were notgenerally known as such but were already under observation by R. F. G.and two that were discovered by Hipparcos to show eclipses but had neverbeen recognized as SBs. With the previously known binaries, there is atotal of 61 definite plus three probable binaries out of a total of 111stars upon which we can adjudicate-a binary fraction of ~58%, justdouble the ~29% found in a sample of randomly selected F stars byNordström et al. (1997). Of the binaries, 52 are SB2 and 12 areSB1. Orbits (some of them still rather preliminary) have been determinedfor the first time for 28 binaries, 21 of which are SB2.Comparison of the CRV stars (a total of 47) with the SB2 binaries hasshown that the two groups have different kinematics. The differenceimplies that on average the CRV stars are 3 to 4 Gyr older than theSB2s, although several of the CRVs appear to be very young. At the sametime the SB2 stars turn out to have about the same kinematics, hence thesame average age, as both binary and normal single F stars from acontrol sample drawn from the Hipparcos catalog. The much older age ofthe bulk of the overluminous CRV F stars may be indicative of anomalousstellar evolution that results in anomalously long main-sequencelifetimes for those stars. The SB1 stars appear to be closer to the CRVsthan to the SB2s and are probably also very old. The properties of the``no-dip'' stars suggest very young age; some of the stars are probablypre-main-sequence (PMS). A few PMS candidates have been identified alsoamong the CRV stars. Thus, overluminous F stars comprising our sampleappear to consist of three distinct groups: mostly young SB2 binarieswith comparably bright components, mostly very old CRV and SB1 stars,and very young no-dip stars.
| HIPPARCOS age-metallicity relation of the solar neighbourhood disc stars
We derive age-metallicity relations (AMRs) and orbital parameters forthe 1658 solar neighbourhood stars to which accurate distances aremeasured by the HIPPARCOS satellite. The sample stars comprise 1382 thindisc stars, 229 thick disc stars, and 47 halo stars according to theirorbital parameters. We find a considerable scatter for thin disc AMRalong the one-zone Galactic chemical evolution (GCE) model. Orbits andmetallicities of thin disc stars show now clear relation each other. Thescatter along the AMR exists even if the stars with the same orbits areselected. We examine simple extension of one-zone GCE models whichaccount for inhomogeneity in the effective yield and inhomogeneous starformation rate in the Galaxy. Both extensions of the one-zone GCE modelcannot account for the scatter in age - [Fe/H] - [Ca/Fe] relationsimultaneously. We conclude, therefore, that the scatter along the thindisc AMR is an essential feature in the formation and evolution of theGalaxy. The AMR for thick disc stars shows that the star formationterminated 8 Gyr ago in the thick disc. As already reported by Grattonet al. (\cite{Gratton_et.al.2000}) and Prochaska et al.(\cite{Prochaska_et.al.2000}), thick disc stars are more Ca-rich thanthin disc stars with the same [Fe/H]. We find that thick disc stars showa vertical abundance gradient. These three facts, the AMR, verticalgradient, and [Ca/Fe]-[Fe/H] relation, support monolithic collapseand/or accretion of satellite dwarf galaxies as likely thick discformation scenarios. Tables 2 and 3 are only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http:/ /cdsweb.u-strasbg.fr/ cgi-bin/qcat?J/ A+A/394/927
| Spectroscopic binary orbits from photoelectric radial velocities. Paper 148: HR 7955
Not Available
| Spectroscopic binary orbits from photoelectric radial velocities. Paper 145: HR 6797
Not Available
| Spectroscopic binary orbits from photoelectric radial velocities. Paper 136: HD 7000
Not Available
| Spectroscopic binary orbits from photoelectric radial velocities. Paper 135: HR 2918
Not Available
| Spectroscopic binary orbits from photoelectric radial velocities. Paper 131: HR 2236
Not Available
| The photoelectric astrolabe catalogue of Yunnan Observatory (YPAC).
The positions of 53 FK5, 70 FK5 Extension and 486 GC stars are given forthe equator and equinox J2000.0 and for the mean observation epoch ofeach star. They are determined with the photoelectric astrolabe ofYunnan Observatory. The internal mean errors in right ascension anddeclination are +/- 0.046" and +/- 0.059", respectively. The meanobservation epoch is 1989.51.
| Ca II H and K Filter Photometry on the UVBY System. II. The Catalog of Observations
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....109.2828T&db_key=AST
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| Long-term photometry of variables at ESO. III. The third data catalogue (1990-1992).
In this paper we present the third catalogue of photometric data in theStroemgren system obtained during the period October 1990-January 1992in the framework of the Long-Term Photometry of Variables (LTPV) programat the European Southern Observatory. The catalogue is available incomputer readable form at the Centre de Donnees de Strasbourg.
| Photometry of Stars in the Field of V431 Orionis
Not Available
| Photometry of Stars in the Field of R Aurigae
Not Available
| Near-infrared spectroscopy of proto-planetary nebulae
Sixteen proto-planetary nebulae were observed with low-resolutioninfrared spectroscopy in the H and K bands, and four were observed inthe L band. In the H band, most of the objects show hydrogen Brackettlines (from n = 10 goes to 4 to n = 20 goes to 4) in absorption. In theK band, absorption bands (delta (nu) = 2) of CO were observed to as highas nu = 6 goes to 4, and in three cases the CO bands are in emission.The CO spectrum of 22272 + 5435 was found to change from emission toabsorption over a 3 month interval. The CO emission most likely arisesfrom collisional excitation resulting from recent episodes of mass loss.One new object which possibly shows weak 3.3 micron emission was found.
| Photographic astrometry of binar and proper-motion stars: 8.
300 trigonometric parallaxes, 15 revised binary-star orbits, and 24 massratios are listed and annotated.
| Stroemgren photometry of F- and G-type stars brighter than V = 9.6. I. UVBY photometry
Within the framework of a large photometric observing program, designedto investigate the Galaxy's structure and evolution, Hβ photometryis being made for about 9000 stars. As a by-product, supplementary uvbyphotometry has been made. The results are presented in a cataloguecontaining 6924 uvby observations of 6190 stars, all south ofδ=+38deg. The overall internal rms errors of one observation(transformed to the standard system) of a program star in the interval6.5
| Stromgren Four-Colour UVBY Photometry of G5-TYPE Hd-Stars Brighter than MV=8.6
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..102...89O&db_key=AST
| Secondary UVBY standards in the Harvard E-regions
Photoelectric uvby photometry for 201 stars which are already UBV (RI)cstandards is presented. The photoelectric data are closely tied to theCousins uvby standards and the stars should be suitable for use asfainter (7-11 mag) secondary standards.
| Large and Kinematically Unbiased Samples of G- and K-Type Stars. III. Evolved Young Disk Stars in the Bright Star Sample
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1989PASP..101...54E&db_key=AST
| Large and kinematically unbiased samples of G- and K-type stars. II - Observations of evolved stars in the Bright Star sample. III - Evolved young disk stars in the Bright Star sample
Four color and RI observations were obtained for a large sample ofG-type and K-type stars in the Bright Star Catalogue. Data are firstpresented for 110 evolved stars. Photometry of evolved young diskpopulation stars have then been calibrated for luminosity, reddening,and metallicity on the basis of results for members of the Hyades andSirius superclusters. New DDO results are given for 120 stars.
| H-beta photometry for UVBY standard stars
Observational campaigns from 1984 to 1986 were made using uvby and betaphotometric systems to monitor a selected sample of late-type variablestars. The beta results are presented here for the 38 uvby standardsthat are not beta standard. A description of the observationaltechniques, reduction procedures, and data accuracy are reported. Thebeta computed values are plotted against the Stroemgren b-y, m1, and c1indices.
| A catalog of bright UVBY beta standard stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1987PASP...99.1184P&db_key=AST
| Instrumental effects and the Stroemgren photometric system
The extent to which the use of different photometers can affect resultson stellar color indices was investigated by simultaneously observing asample of widely different stars with several uvby photometric systemsavailable at the ESO, La Silla, Chile. In one instance, the ESO 50-cmtelescope and the four-channel photometer at the Danish 50-cm telescopewere used simultaneously. The reductions were performed separately oneach data set, using a linear color transformation procedure. Theresults agree with theoretical investigations which showed thatsubstantial errors can arise from the nonconformity of passbands. It isemphasized that it is necessary to use separate color transformationsfor various stellar types and classes and for different interstellarreddenings.
| A UVBY beta survey of northern-hemisphere active binaries. I - The observations
A recent detailed calibration of the uvby photometric system forlate-type stars has opened the possibility of studying photometriceffects of stellar activity in the RS CVn group of binaries. A uvby betaphotometric study of 72 northern-hemisphere binary systems with activechromospheres has been carried out at the Roque de los MuchachosObservatory (La Palma, Canary Islands) with a People's photometerattached to the JKT 1.0 m telescope. The standarized colors and Vmagnitudes are presented as a function of the orbital phase, along withan indication of their accuracy. A detailed discussion of atmosphericextinction, characteristics of the photometric system, andtransformation coefficients is also included.
| Large and kinematically unbiased samples of G and K type stars. I - The dwarfs
Four-color, H-beta, and (R,I) photometry for the little-evolvedmain-sequence stars from the Bright Star Catalogue, South Galactic Pole,Griffin (1971), and Moore-Paddock-Wayman (Moore and Paddock 1950, andWayman 1960) samples are analyzed. The luminosity and heavy-elementabundances for these stars are calculated in terms of the Hyadessupercluster, the Wolf 630 group, the Sirius supercluster, and theKapteyn star group. The data reveal the presence of a metal-abundancedependent discontinuity near M(v) = +7 mag in the photometric parametersof dwarfs. The distributions of the abundances and the space motions ofthe sample stars are discussed.
| Four-colour UVBY and H-beta photometry of A5 to G0 stars brighter than 8.3 M
A Stromgren uvby survey is made of nearly all the Henry Draper stars oftypes A5 to G0 whose brightnesses exceed 8.3 m. H-beta and uvbyphotometry is obtained for nearly 2000 of the most metal-weak starsfound and about 500 other stars of interest. The photometric results arearranged in a catalog containing 27,096 uvby and 7223 beta measurementsof 14,816 stars. The catalog seeks to provide a complete, kinematicallyunbiased sample, limited in magnitude, of late F-type stars belonging tothe intermediate population II. In combination with kinematical data,this sample will be ideally suited to investigate the history of ourGalaxy by studying the correlations between age, chemical composition,and kinematics. The transformations between instrumental and standardphotometric systems are discussed in considerable detail. It is shownthat the systematic difference between northern and southern uvbycatalogs has two probable causes. Attention is also given to a smallsystematic difference between the northern and southern betameasurements. A discussion of uvby photometry made on cloudy nights isalso included.
| A catalogue of stellar spectrophotometric data
A list of 378 sets of stellar energy distributions for 356 stars basedon photoelectric spectrophotometry is presented. Data from eight sourceshave been transformed to the Hayes-Latham calibration of Alpha Lyrae.The procedure follows that of Breger (1976) and the present list extendsprevious data, especially for stars of earliest and intermediatespectral types.
| Possible nearby stars brighter than tenth magnitude
Basic data are compiled for 447 stars brighter than 10th visualmagnitude which may be within 25 pc of the sun and are missing from boththe Gliese (1969) and the Woolley et al. (1970) catalogs of nearbystars. The list includes 245 stars with photometric parallaxes, 17 starswith trigonometric parallaxes, and nine stars with dynamical parallaxes,all of which parallaxes are at least 0.040 arcsec, as well as 176 likelycandidates. The stars are grouped into six categories according to thereliability of absolute-magnitude estimates and ranked within each groupon the basis of calculated distance. The distance estimates incorporatea kinematic correction to the photometric parallaxes which is based onthe size of a star's proper motion. A list of stars brighter than 10thmag which appear in the Gliese but not in the Woolley et al. catalog isalso provided to facilitate cross-reference with existing catalogs ofnearby stars.
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Группы:
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Наблюдательные данные и астрометрия
| Созвездие: | Малый Пёс |
| Прямое восхождение: | 07h36m34.70s |
| Склонение: | +05°51'42.0" |
| Видимая звёздная величина: | 5.91 |
| Расстояние: | 43.63 парсек |
| Собственное движение RA: | -107.4 |
| Собственное движение Dec: | 26.7 |
| B-T magnitude: | 6.607 |
| V-T magnitude: | 5.956 |
Каталоги и обозначения:
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