Оглавление
Изображения
Загрузить ваше изображение
DSS Images Other Images
Публикации по объекту
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
| The N2K Consortium. VII. Atmospheric Parameters of 1907 Metal-rich Stars: Finding Planet-Search Targets
We report high-precision atmospheric parameters for 1907 stars in theN2K low-resolution spectroscopic survey, designed to identify metal-richFGK dwarfs likely to harbor detectable planets. Of these stars, 284 arein the ideal temperature range for planet searches,Teff<=6000 K, and have a 10% or greater probability ofhosting planets based on their metallicities. The stars in thelow-resolution spectroscopic survey should eventually yield >60 newplanets, including 8-9 hot Jupiters. Short-period planets have alreadybeen discovered orbiting the survey targets HIP 14810 and HD 149143.
| 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
| Intermediate-Brightness Spectrophotometric Standards. Standards Near +40° Declination
The second stage in our program to compile a list of regionalintermediate-brightness spectrophotometric standards has been completed.We have obtained spectral energy distributions for 24 stars withmagnitudes near +40° declination. The range λλ31007600 Å was studied with a spectral resolution of 50 Å. Therelative rms error of our results in the visible is 1 2%, increasing to3 5% toward the edges of the studied wavelength interval. All the starsare referenced to a single standard, the circumpolar star HD 221525. Theenergy distributions were used to compute color indices in the UBV,WBVR, and UPXY ZV S systems, as well as in the system of the TYCHOcatalog. The computed and observed values for stars in common with theTYCHO catalog are compared.
| MK classification and photometry of stars used for time and latitude observations at Mizusawa and Washington
MK spectral classifications are given for 591 stars which are used fortime and latitude observations at Mizusawa and Washington. Theclassifications in the MK system were made by slit spectrograms ofdispersion 73 A/mm at H-gamma which were taken with the 91 cm reflectorat the Okayama Astrophysical Observatory. Photometric observations in UBV were made with the 1-meter reflector at the Flagstaff Station of U.S.Naval Observatory. The spectrum of HD 139216 was found to show a strongabsorption line of H-beta. The following new Am stars were found:HD9550, 25271, 32784, 57245, 71494, and 219109. The following new Apstars were found: HD6116, 143806, 166894, 185171, and 209260. The threestars, HD80492, 116204, and 211376, were found to show the emission inCaII H and K lines.
| UBV photometry of stars whose positions are accurately known. III
UBV photometric observations of 417 stars at BD declination 35-49 degfrom the NPZT(74) catalog of Yasuda et al. (1982) and the AGK3R catalogof Corben (1978), obtained with the 40-cm Cassegrain reflector atKvistaberg Observatory during 1984-1985, are reported. The data arepresented in tables, and the mean errors per observation are given as0.016 mag in V, 0.011 mag in B-V, 0.012 mag in U-B for U less than 10,and 0.026 mag in U-B for U greater than 10.
| Preliminary catalog of the declinations of 96 stars of the international program, compiled from Kitab PZT observations
Not Available
| UBV Photoelectric Photometry of 259 PZT Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980PASP...92..215G&db_key=AST
| Estimation of spectral classifications for bright northern stars with interesting Stromgren indices
The purpose of this investigation is to provide spectroscopic observerswith finding lists of potentially interesting objects. From anunpublished UVBY catalogue of 7026 northern stars (mostly brighter than8.3m) 1094 objects with interesting combinations of UVBY indices havebeen selected. Most stars with post-HD classifications have beenexcluded, as well as late F dwarfs belonging to the intermediatepopulation II. For the 792 remaining stars estimated spectralclassifications are given. The techniques and experience from a previouspaper dealing with southern stars have been utilized here. Among thepredicted spectral classifications are 40 OB stars; 262 Ap, Am, or Fmstars; 16 supergiants of types A to G; 110 bright giants of types A to K(class II); 156 double stars or objects with composite spectra; 26 lateF dwarfs; 91 weak-lined dwarf and giant stars of types F to K, includingearly F-type population II field blue stragglers; and a few possiblefield horizontal branch stars, lambda Bootis-type stars, and late-typehalo giants.
|
Добавить новую статью
Внешние ссылки
- - Внешних ссылок не найдено -
Добавить внешнюю ссылку
Группы:
|
Наблюдательные данные и астрометрия
| Созвездие: | Персей |
| Прямое восхождение: | 04h25m19.85s |
| Склонение: | +39°03'09.0" |
| Видимая звёздная величина: | 8.239 |
| Расстояние: | 121.507 парсек |
| Собственное движение RA: | -12.1 |
| Собственное движение Dec: | -68.6 |
| B-T magnitude: | 9.05 |
| V-T magnitude: | 8.306 |
Каталоги и обозначения:
|
