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A new stellar library in the region of the CO index at 2.3 μm. New index definition and empirical fitting functions
Context: The analysis of unresolved stellar populations demandsevolutionary synthesis models with realistic physical ingredients andextended wavelength coverage. Aims: We quantitatively describe thefirst CO bandhead at 2.3 μm to allow stellar population models toprovide improved predictions in this wavelength range. Methods: Weobserved a new stellar library with a better coverage of the stellaratmospheric parameter space than in earlier works. We performed adetailed analysis of the robustness of previous CO index definitionswith spectral resolution, wavelength calibration, signal-to-noise ratio,and flux calibration. Results: We define a new line-strength index forthe first CO bandhead at 2.3 μm, D_CO, better suited for stellarpopulation studies than previous index definitions. We derive empiricalfitting functions for the CO feature as a function of the stellarparameters (T_eff, log g and [Fe/H]), showing a detailed quantitativemetallicity dependence.
| Medium-resolution Isaac Newton Telescope library of empirical spectra - II. The stellar atmospheric parameters
We present a homogeneous set of stellar atmospheric parameters(Teff, logg, [Fe/H]) for MILES, a new spectral stellarlibrary covering the range λλ 3525-7500Å at2.3Å (FWHM) spectral resolution. The library consists of 985 starsspanning a large range in atmospheric parameters, from super-metal-rich,cool stars to hot, metal-poor stars. The spectral resolution, spectraltype coverage and number of stars represent a substantial improvementover previous libraries used in population synthesis models. Theatmospheric parameters that we present here are the result of aprevious, extensive compilation from the literature. In order toconstruct a homogeneous data set of atmospheric parameters we have takenthe sample of stars of Soubiran, Katz & Cayrel, which has very welldetermined fundamental parameters, as the standard reference system forour field stars, and have calibrated and bootstrapped the data fromother papers against it. The atmospheric parameters for our clusterstars have also been revised and updated according to recent metallicityscales, colour-temperature relations and improved set of isochrones.
| Medium-resolution Isaac Newton Telescope library of empirical spectra
A new stellar library developed for stellar population synthesismodelling is presented. The library consists of 985 stars spanning alarge range in atmospheric parameters. The spectra were obtained at the2.5-m Isaac Newton Telescope and cover the range λλ3525-7500 Å at 2.3 Å (full width at half-maximum) spectralresolution. The spectral resolution, spectral-type coverage,flux-calibration accuracy and number of stars represent a substantialimprovement over previous libraries used in population-synthesis models.
| Catalogue of [Fe/H] determinations for FGK stars: 2001 edition
The catalogue presented here is a compilation of published atmosphericparameters (Teff, log g, [Fe/H]) obtained from highresolution, high signal-to-noise spectroscopic observations. This newedition has changed compared to the five previous versions. It is nowrestricted to intermediate and low mass stars (F, G and K stars). Itcontains 6354 determinations of (Teff, log g, [Fe/H]) for3356 stars, including 909 stars in 79 stellar systems. The literature iscomplete between January 1980 and December 2000 and includes 378references. The catalogue is made up of two tables, one for field starsand one for stars in galactic associations, open and globular clustersand external galaxies. The catalogue is distributed through the CDSdatabase. Access to the catalogue with cross-identification to othersets of data is also possible with VizieR (Ochsenbein et al.\cite{och00}). The catalogue (Tables 1 and 2) is only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/373/159 and VizieRhttp://vizier.u-strasbg.fr/.
| Detailed analysis of a sample of Li-rich giants
A detailed analysis has been carried out for a sample of 16 red giantsshowing a strong Li I 670.8 nm line. Ten of them were detected in asurvey by Castilho et al. (1998), and the other 6 stars are Li-richgiants selected from the literature. Element abundances in the sampleLi-rich giants are similar to those in normal red giants, differing onlyby their high Li abundance and infrared excess. This suggests thatLi-rich giants may correspond to a phase of stellar evolution of normalred giants, when Li is produced and transported to the atmosphere.
| Li-rich giants: A survey based on IRAS colours
In a previous work we studied the IRAS colours of known Li-rich redgiants and showed that they have flux ratiosF12/F25 and F25/F60 in welldefined ranges. By using this result as a selection criterion, weprepared a list of 280 IRAS Point Source candidates to be Li-rich giantstars. Up to the present we have obtained spectra for 57% of our targetlist. We identified five stars showing a strong LiI 670.079 nm line andsix ones with a Li line of medium strength. Most of the candidates showfeatures typical of normal giants having circumstellar dust, asindicated by their IRAS colours. Observations collected at theLaboratorio Nacional de Astrofisica - LNA, Brazil; Observatoire de HauteProvence - OHP, France; European Southern Observatory - ESO, Chile.
| High resolution spectra of Li-rich giants
We present high resolution spectra for 5 Lithium rich red giantsdiscovered in an ongoing survey based on IRAS colours. Other 6 starsshowing medium strength of the Li line are also presented here. Highresolution one order spectra for the program stars were obtained at theLaboratorio Nacional de Astrofisica (LNA) and Observatoire de HauteProvence (OHP), and the echelle spectrum of HD 146850 was obtained atthe European Southern Observatory (ESO). The 11 one order spectra andthe 40 orders of the echelle spectra were calibrated in wavelength andnormalized in relative intensity.
| Analysis of the moderately Li-rich giant HD 146850.
We report the identification of 3 Li-rich giants discovered in anongoing survey based on IRAS colours. A detailed analysis of one ofthese, HD 146850, is presented here. High-resolution spectra wereobtained for this star, using CASPEC at the 3.6m telescope of ESO. Wederived the stellar parameters (T_eff_, log g, [M/H])=4000, 1.5, -0.3. Alithium abundance of ɛ(Li)=1.6 is found, whereas [C/Fe]~0.0 and[N/Fe]~-0.1 indicating that no convective mixing has occurred. Theabundances of oxygen [O/Fe]=~+0.1 and α-elements[Mg/Fe]=[Ti/Fe]=[Ca/Fe]=~0.0 suggest that we are dealing with a diskstar, for which the radial velocity v_r_=42km/s is also moderate.
| A search for Li-rich giants
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| Takýmyýldýz: | Tekboynuz |
| Sað Açýklýk: | 06h23m58.81s |
| Yükselim: | -09°04'07.7" |
| Görünürdeki Parlaklýk: | 7.547 |
| Uzaklýk: | 833.333 parsek |
| özdevim Sað Açýklýk: | -2.5 |
| özdevim Yükselim: | 1.7 |
| B-T magnitude: | 9.724 |
| V-T magnitude: | 7.727 |
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