Contingut
Imatges
Carregar la teva Imatge
DSS Images Other Images
Articles Relacionats
Fe II Emission in 14 Low-Redshift Quasars. I. Observations
We present the spectra of 14 quasars with a wide coverage of restwavelengths from 1000 to 7300 Å. The redshift ranges from z=0.061to 0.555 and the luminosity from MB=-22.69 to -26.32. Thesespectra of high quality result from combining Hubble Space Telescopespectra with those taken from ground-based telescopes. We describe theprocedure of generating the template spectrum of Fe II line emissionfrom the spectrum of a narrow-line Seyfert 1 galaxy, I Zw 1, that coverstwo wavelength regions of 2200-3500 and 4200-5600 Å. Our templateFe II spectrum is semiempirical in the sense that the synthetic spectrumcalculated with the CLOUDY photoionization code is used to separate theFe II emission from the Mg II λ2798 line. The procedure ofmeasuring the strengths of Fe II emission lines is twofold: (1)subtracting the continuum components by fitting models of the power-lawand Balmer continua in the continuum windows, which are relatively freefrom line emissions, and (2) fitting models of the Fe II emission basedon the Fe II template to the continuum-subtracted spectra. From 14quasars including I Zw 1, we obtained the Fe II fluxes in fivewavelength bands (U1 [2200-2660 Å], U2 [2660-3000 Å], U3[3000-3500 Å], O1 [4400-4700 Å], and O2 [5100-5600Å]), the total flux of Balmer continuum, and the fluxes of Mg IIλ2798, Hα, and other emission lines, together with the fullwidths at half-maximum (FWHMs) of these lines. Regression analysis wasperformed by assuming a linear relation between any two of thesequantities. Eight correlations were found with a confidence level higherthan 99%: (1) larger Mg II FWHM for larger Hα FWHM, (2) largerΓ for fainter MB, (3) smaller Mg II FWHM for largerΓ, (4) larger Mg II FWHM for smaller Fe II(O1)/Mg II, (5) largerMBH for smaller Γ, (6) larger MBH forsmaller Fe II(O1)/Mg II, (7) larger [O III]/Hβ for larger Mg IIFWHM, and (8) larger Fe II(O1)/Mg II for larger Fe II(O1)/Fe II(U1). Thefact that six of these eight are related to FWHM or MBH(~FWHM2) may imply that MBH is a fundamentalquantity that controls Γ or the spectral energy distribution (SED)of the incident continuum, which in turn controls the Fe II emission.Furthermore, it is worthy of noting that Fe II(O1)/Fe II(U1) is found totightly correlate with Fe II(O1)/Mg II, but not with Fe II(U1)/Mg II.
| 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
| Classification of Population II Stars in the Vilnius Photometric System. II. Results
The results of photometric classification of 848 true and suspectedPopulation II stars, some of which were found to belong to Population I,are presented. The stars were classified using a new calibrationdescribed in Paper I (Bartkevicius & Lazauskaite 1996). We combinethese results with our results from Paper I and discuss in greaterdetail the following groups of stars: UU Herculis-type stars and otherhigh-galactic-latitude supergiants, field red horizontal-branch stars,metal-deficient visual binaries, metal-deficient subgiants, stars fromthe Catalogue of Metal-deficient F--M Stars Classified Photometrically(MDPH; Bartkevicius 1993) and stars from one of the HIPPARCOS programs(Bartkevicius 1994a). It is confirmed that high galactic latitudesupergiants from the Bartaya (1979) catalog are giants or even dwarfs.Some stars, identified by Rose (1985) and Tautvaisiene (1996a) as fieldRHB stars, appear to be ordinary giants according to our classification.Some of the visual binaries studied can be considered as physical pairs.Quite a large fraction of stars from the MDPH catalog are found to havesolar metallicity. A number of new possible UU Herculis-type stars, RHBstars and metal-deficient subgiants are identified.
| 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.
| The Arcturus Group
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971PASP...83..271E&db_key=AST
| Colors, luminosities, and motions of the nearer G-type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1964AJ.....69..570E&db_key=AST
|
Enviar un nou article
Enllaços Relacionats
- - No s'ha trobat enllaços -
Enviar un nou enllaç
Membre dels grups següents:
|
Dades d'Observació i Astrometria
| Constel·lació: | Corona Borealis |
| Ascensió Recta: | 15h42m16.29s |
| Declinació: | +29°37'22.5" |
| Magnitud Aparent: | 8.568 |
| Distancia: | 52.11 parsecs |
| Moviment propi RA: | -68.8 |
| Moviment propi Dec: | -164.5 |
| B-T magnitude: | 9.381 |
| V-T magnitude: | 8.636 |
Catàlegs i designacions:
|
