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Behavior of Li abundances in solar-analog stars. Evidence for line-width dependence
Context: It is known that the surface lithium abundances of fieldsolar-analog G dwarfs show a large dispersion of ⪆2 dex (among whichour Sun is located at the lower end) despite the similarity of stellarparameters, and planet-host stars tend to show comparatively lower Liabundances in the narrow T_eff range. Aims: To investigate thereason for these phenomena, an extensive study of Li abundances andtheir dependence on stellar parameters was carried out for a homogeneoussample of 118 selected solar analogs based on high-dispersion spectraobtained at Okayama Astrophysical Observatory. Methods: Theatmospheric parameters were spectroscopically determined by using theequivalent widths of Fe i and Fe ii lines, the ages/masses wereestimated from stellar evolutionary tracks, and the width of themacrobroadening (rotation plus macroturbulence) function as well as Liabundances (A_Li) were established by spectrum-fitting analyses.Results: The resulting A_Li vs. T_eff relation revealed a characteristicinverse-triangle-like distribution enclosed by two clear-cut boundaries(the slanted one running from ~5900 K to ~5800 K and the vertical one at~5700 K), while the Sun is located around its lowest apex. Moresignificantly, A_Li in this region of large dispersion was found toclosely correlate with the macrobroadening width (v_r+m), which isconsidered to be the most important parameter. Conclusions: With areasonable assumption that the difference of rotational velocity ismainly responsible for the variety of v_r+m, we may conclude that thestellar angular momentum plays the decisive role in determining thesurface Li abundances of solar-analog stars in the T_eff range of~5900-5700 K. The low-Li tendency of planet-host stars may thus beinterpreted in terms of rotational characteristics.Based on observations carried out at Okayama Astrophysical Observatory(Okayama, Japan). Tables 2-6 are only available in electronic form atthe 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/468/663
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
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| The Vienna-KPNO search for Doppler-imaging candidate stars. I. A catalog of stellar-activity indicators for 1058 late-type Hipparcos stars
We present the results from a spectroscopic Ca ii H&K survey of 1058late-type stars selected from a color-limited subsample of the Hipparcoscatalog. Out of these 1058 stars, 371 stars were found to showsignificant H&K emission, most of them previously unknown; 23% withstrong emission, 36% with moderate emission, and 41% with weak emission.These spectra are used to determine absolute H&K emission-linefluxes, radial velocities, and equivalent widths of theluminosity-sensitive Sr ii line at 4077 Ä. Red-wavelengthspectroscopic and Strömgren y photometric follow-up observations ofthe 371 stars with H&K emission are used to additionally determinethe absolute Hα -core flux, the lithium abundance from the Li i6708 Å equivalent width, the rotational velocity vsin i, theradial velocity, and the light variations and its periodicity. Thelatter is interpreted as the stellar rotation period due to aninhomogeneous surface brightness distribution. 156 stars were found withphotometric periods between 0.29 and 64 days, 11 additional systemsshowed quasi-periodic variations possibly in excess of ~50 days. Further54 stars had variations but no unique period was found, and four starswere essentially constant. Altogether, 170 new variable stars werediscovered. Additionally, we found 17 new SB1 (plus 16 new candidates)and 19 new SB2 systems, as well as one definite and two possible new SB3systems. Finally, we present a list of 21 stars that we think are mostsuitable candidates for a detailed study with the Doppler-imagingtechnique. Tables A1--A3 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
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| Takýmyýldýz: | Buyuk Ayi |
| Sað Açýklýk: | 09h33m28.74s |
| Yükselim: | +46°13'43.3" |
| Görünürdeki Parlaklýk: | 8.378 |
| Uzaklýk: | 46.926 parsek |
| özdevim Sað Açýklýk: | -20.2 |
| özdevim Yükselim: | 3.1 |
| B-T magnitude: | 9.174 |
| V-T magnitude: | 8.444 |
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