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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
| An improved metal abundance calibration for the Washington system
The determination of metal abundances for individual giants fromWashington photometry is revised, with several significant improvementsincorporated. The solar-abundance two-color relations are revamped withthe inclusion of new observations of a large sample of solar-abundancegiants with small reddenings, especially those with late-K spectraltypes. The new relations are very similar to the original ones derivedin C76 except for a zero-point offset. A new temperature index, M-T2, isinvestigated, as well as a new abundance index, C-T1, in addition to thestandard indices. The M-T2 index has a much broader baseline and thus amuch larger range than T1-T2, and is therefore less susceptible tophotometric errors. The significant decrease in abundance sensitivityfor cooler stars, suspected by previous investigations, is confirmed byincluding observations of a number of giants with a range in temperaturein each of a large sample of open and globular clusters. A procedure forcorrecting the abundance indices for cool stars is derived whichsignificantly improves the metallicity determination.
| Scanner Abundance Studies.IV. Observations of Some Strong-Cn and Miscellaneous Evolved Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972ApJ...173..619T&db_key=AST
| Stars with Strong Cyanogen Absorption
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971ApJ...163...75S&db_key=AST
| A photoelectric investigation of strong cyanogen stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970AJ.....75...41M&db_key=AST
| Spectral and Luminosity Classifications and Measurements of the Strength of Cyanogen Absorption for Late-Type Stars from Objective-Prism Spectra.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1961ApJ...134..809Y&db_key=AST
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