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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
| On the Variability of F1-F9 Luminosity Class III-V Stars
Hipparcos Satellite photometry of F1-F9 luminosity class III-V starsindicates that most are not particularly variable. A few stars for whichfurther study is desirable are identified.
| The ROSAT Bright Survey: II. Catalogue of all high-galactic latitude RASS sources with PSPC countrate CR > 0.2 s-1
We present a summary of an identification program of the more than 2000X-ray sources detected during the ROSAT All-Sky Survey (Voges et al.1999) at high galactic latitude, |b| > 30degr , with countrate above0.2 s-1. This program, termed the ROSAT Bright Survey RBS, isto more than 99.5% complete. A sub-sample of 931 sources with countrateabove 0.2 s-1 in the hard spectral band between 0.5 and 2.0keV is to 100% identified. The total survey area comprises 20391deg2 at a flux limit of 2.4 x 10-12 ergcm-2 s-1 in the 0.5 - 2.0 keV band. About 1500sources of the complete sample could be identified by correlating theRBS with SIMBAD and the NED. The remaining ~ 500 sources were identifiedby low-resolution optical spectroscopy and CCD imaging utilizingtelescopes at La Silla, Calar Alto, Zelenchukskaya and Mauna Kea. Apartfrom completely untouched sources, catalogued clusters and galaxieswithout published redshift as well as catalogued galaxies with unusualhigh X-ray luminosity were included in the spectroscopic identificationprogram. Details of the observations with an on-line presentation of thefinding charts and the optical spectra will be published separately.Here we summarize our identifications in a table which contains opticaland X-ray information for each source. As a result we present the mostmassive complete sample of X-ray selected AGNs with a total of 669members and a well populated X-ray selected sample of 302 clusters ofgalaxies with redshifts up to 0.70. Three fields studied by us remainwithout optical counterpart (RBS0378, RBS1223, RBS1556). While the firstis a possible X-ray transient, the two latter are isolated neutron starcandidates (Motch et al. 1999, Schwope et al. 1999).
| The ROSAT Wide Field Camera Extragalactic Survey
We report the results of a new analysis of the ROSAT Wide Field Camera(WFC) all-sky survey data, designed to detect extragalactic sources ofextreme ultraviolet (EUV) radiation in regions of low Galactic N_H. Weidentify a total of 19 active galactic nuclei (AGN), more than doublethe number of confirmed AGN in the published WFC (2RE) survey. Oursample contains eight narrow-line Seyfert 1 galaxies, making this thefirst reasonably sized, complete sample of these extreme AGN, along withsix broad-line Seyfert 1s and five BL Lacertae objects. TheseEUV-selected sources typically have steep soft X-ray spectra with a meanpower-law energy index alpha_X ~ -2. The derived AGN luminosity functionis rather flat and appears to cut off above a luminosity of 10^46 ergs^-1 keV^-1, measured monochromatically at 200 eV. Narrow-line Seyfert1s account for roughly half of the local (z ~ 0) volume emissivity inthe EUV band.
| The Second Extreme Ultraviolet Explorer Right Angle Program Catalog
We present the detection of 235 extreme ultraviolet sources, of which169 are new detections, using the Extreme Ultraviolet Explorer's (EUVE)Right Angle Program (RAP) data. This catalog includes observations sincethe first EUVE RAP catalog (1994 January) and covers 17% of the sky. TheEUVE RAP uses the all-sky survey telescopes (also known as``scanners''), mounted at right angles to the Deep Survey andspectrometer instruments, to obtain photometric data in four wavelengthbands centered at ~100 Å (Lexan/B), ~200 Å (Al/Ti/C), ~400Å (Ti/Sb/Al), and ~550 Å (Sn/SiO). This allows the RAP toaccumulate data serendipitously during pointed spectroscopicobservations. The long exposure times possible with RAP observationsprovide much greater sensitivity than the all-sky survey. We presentEUVE source count rates and probable source identifications from theavailable catalogs and literature. The source distribution is similar toprevious extreme ultraviolet (EUV) catalogs with 2% early-type stars,45% late-type stars, 8% white dwarfs, 6% extragalactic, 24% with no firmclassification, and 15% with no optical identification. We also present36 detections of early-type stars that are probably the result ofnon-EUV radiation. We have detected stellar flares from approximately 12sources, including: EUVE J0008+208, M4 star G32-6 (EUVE J0016+198), anew source EUVE J0202+105, EUVE J0213+368, RS CVn V711 Tau (EUVEJ0336+005), BY Draconis type variable V837 Tau (EUVE J0336+259), the newK5 binary EUVE J0725-004, EUVE J1147+050, EUVE J1148-374, EUVE J1334-083(EQ Vir), EUVE J1438-432 (WT 486/487), EUVE J1808+297, and the M5.5estar G208-45 (EUVE J1953+444). We present sample light curves for thebrighter sources.
| The ROSAT all-sky survey catalogue of optically bright main-sequence stars and subgiant stars
We present X-ray data for all main-sequence and subgiant stars ofspectral types A, F, G, and K and luminosity classes IV and V listed inthe Bright Star Catalogue that have been detected as X-ray sources inthe ROSAT all-sky survey; several stars without luminosity class arealso included. The catalogue contains 980 entries yielding an averagedetection rate of 32 percent. In addition to count rates, sourcedetection parameters, hardness ratios, and X-ray fluxes we also listX-ray luminosities derived from Hipparcos parallaxes. The catalogue isalso available in electronic form via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| X-ray/optical observations of stars with shallow convection zones (A8-G2 V)
We present Walraven photometry and ROSAT All-Sky Survey data for asample of 173 bright main-sequence stars with spectral types between A8Vand G2V\@. These observations are part of a study of the onset ofmagnetic surface activity along the main sequence. Values for theeffective temperature, surface gravity and interstellar reddening havebeen obtained from a comparison of the observed Walraven colours withtheoretical values. These parameters have been used to derive accurateX-ray\ surface flux densities.
| Identification of soft high galactic latitude RASS X-ray sources. I. A complete count-rate limited sample
We present a summary of spectroscopic identifications for a completesample of bright soft high galactic latitude X-ray sources drawn fromthe ROSAT All-Sky Survey which have PSPC count-rates CR > 0.5 {ctss}(-1) and hardness ratios HR1 < 0. Of a total of 397 sources, 270had catalogued counterparts although most of these were not previouslyknown as X-ray sources; of the remaining 127 sources neither X-ray noroptical properties were previously known. Of the whole sample of verysoft X-ray sources 155 were also discovered by the Wide-Field-Camera onboard ROSAT. We present spectroscopic identifications of 108 sources andother identifications for further 18 sources; 1 source remainsunidentified so far. In practically all cases a unique opticalcounterpart exists facilitating identification. The largest sourceclasses are AGN, magnetic cataclysmic variables, and hot white dwarfs.Based in part on observations with the ESO/MPI 2.2m telescope at LaSilla, Chile
| A Catalogue of Correlations Between Eclipsing Binaries and Other Categories of Double Stars
Among the 9110 stars in The Bright Star Catalogue, there are 225eclipsing or ellipsoidal variables. A search has been made for these incatalogues of spectroscopic binaries, visual double or multiple stars,speckle interferometry, occulation binaries, and galatic clusters. Themajority of the photometric binaries are also members of groups ofhigher multiplicity. The variables are in systems ranging from one to 91stars, five on the average. 199 are either spectroscopic binaries (SB)or stars with variable radial velocity, with orbital periods known for160. Photometric periods are lacking for 48 while SB periods areavailable for 23 of these. Observers with photoelectric equipment areencouraged to plan observations to test if the SB periods are consistentwith photometric data. Observers are likewise encouraged to examinethose stars for which the photometric and SB periods appear to beinconsistent. Parallaxes are available for 86 of the stars, 41 of themindicating distances nearer than 50 parsecs.
| 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
| The position corrections of 1400 stars observed with PA II in San Juan.
Not Available
| Longterm Photometry of Variables at ESO - Part Two - the Second Data Catalogue 1986-1990
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..102...79S&db_key=AST
| Fifth fundamental catalogue. Part 2: The FK5 extension - new fundamental stars
The mean positions and proper motions for 3117 new fundamental starsessentially in the magnitude range about 4.5 to 9.5 are given in thisFK5 extension. Mean apparent visual magnitude is 7.2 and is on average2.5 magnitudes fainter then the basic FK5 which has a mean magnitude of4.7. (The basic FK5 gives the mean positions and proper motions for theclassical 1535 fundamental stars). The following are discussed: theobservational material, reduction of observations, star selection, andthe system for the FK5 extension. An explanation and description of thecatalog are given. The catalog of 3117 fundamental stars for the equinoxand epoch J2000.0 and B1950.0 is presented. The parallaxes and radialvelocities for 22 extension stars with large forecasting effects aregiven. Catalogs used in the compilation of the FK5 fundamental catalogare listed.
| Long-term photometry of variables at ESO. I - The first data catalogue (1982-1986)
This paper presents the catalog of photometric data in the Stromgrensystem obtained during the first four years (October 1982 - September1986) of the Long-Term Photometry of Variables (LTPV) program at ESO.The data are available in computer-readable form.
| Weak-lined F-type stars in the Geneva system
A diagram of m2 vs B2-V1 is used to segregate weak-lined F-type stars inGeneva photometric studies and to compare the corresponding metalabundances to those derived with the Stromgren system. The referencesequence of the m2 vs B2-V1 diagram is revised with a novel delta-m2calibration in terms of Fe/H. The systems are found to perform similarlyin both detecting the weak-lined F-types and in determining the ironabundances.
| The extension of the MK spectral classification system to the intermediate population II F type stars
A grid of metal-weak spectral-classification standards is used tosystematically extend the MK spectral-classification system to F-typestars of the intermediate population II. The present method allowsmetal-weak program stars to be compared with standards of similarmetallicity and effective temperature. The results demonstrate that theintermediate population II is very homogeneous. Excellent agreement isobtained between the classifications of the present extended system anduvby-beta photometric results.
| The eclipsing binary system HD208496
New photoelectric observations of the 6th magnitude suspected eclipsingbinary system HD208496 are presented. A Wilson-Devinney light curvesolution reveals a detached system with components approaching theterminal age main sequence. The orbital period is suspected to bevariable.
| The 68th Name-List of Variable Stars
Not Available
| Photometric variability of some early-type stars
Photometric observations of 12 variable early type stars are presented.The properties of individual stars are discussed, and an attempt is madeto interpret their variability. The information presented on the starsincludes the HD number and other identification, the observing runs, theperiodicity of the variations, an error estimate, and a tentativeclassification of each star.
| HD 208496 (HR8369): a Double-Lined Eclipsing Binary
Not Available
| The Bright Eclipsing Binary HD 208496
Not Available
| Nouvelle recherche de periodes d'etoiles Ap observees a ESO-VII
Not Available
| Photometric boxes in the four-color system
Photometric boxes derived from the latest four-color catalogue compiledby Hauck and Mermilliod (1980) containing uvby and H-beta observationsfor more than 15,000 stars are discussed. The construction andpopulation of stellar boxes, the distribution of boxes with spectraltype, the relations between a geneva box and a four-color box, and theuse of stellar boxes for photometric classification are considered. Itis concluded that the method of stellar boxes is a very useful tool inphotometric investigation.
| The chemical evolution of the solar neighborhood. I - A bias-free reduction technique and data sample
The possible ways of measuring the age-metallicity relation for thegalactic disk in the neighborhood of the sun are discussed. It is shownthat the use of a field star sample chosen on the basis of effectivetemperature introduces a bias which results in a monotonic increase inthe metal abundance of the disk with time. However, if theage-metallicity relation for the disk can be shown to satisfy certaincriteria, the bias introduced in such a sample can be neglected: thegalactic disk apparently satisfies the criteria. It is concluded that asample analyzed through the use of uvby and H(beta) photometry inconjunction with a self-consistent set of theoretical isochronesprovides the least biased, most accurate estimate of the age-metallicityrelation for the disk.
| H_alpha Photometry of Late-type Stars. II. F and G Type Dwarf Stars South of the Equator
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966MNRAS.131..467P&db_key=AST
| Bright Southern BV-Stars
Not Available
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הכנס מאמר חדש
לינקים קשורים
הכנס לינק חדש
משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | אינדיאני |
| התרוממות ימנית: | 21h58m30.10s |
| סירוב: | -59°00'44.0" |
| גודל גלוי: | 6.12 |
| מרחק: | 66.489 פארסק |
| תנועה נכונה: | 5.4 |
| תנועה נכונה: | 26.4 |
| B-T magnitude: | 6.697 |
| V-T magnitude: | 6.195 |
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INHABITED SKY
