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The Ca II infrared triplet as a stellar activity diagnostic. II. Test and calibration with high resolution observations
Aims.We report on our analysis of the high resolution spectra (R≈86000) of a sample of 42 late-type active stars (with measured{log{R'_HK}} spanning from ≈{ -}3 to ≈{ -}5) acquired with theItalian 3.6 m Telescopio Nazionale Galileo (TNG) using the SARGspectrometer in the 4960-10 110 Å range. The high quality of thespectra and the good activity-level coverage allow us to measure twodifferent chromospheric indicators that can be derived from the Ca iiinfrared triplet (Ca ii IRT) lines: the residual equivalent width (EQW)and the chromospheric indicator {R_IRT}. The aim of this work isdetermine and test the best way of deriving activity-level informationand errors from the Ca ii IRT lines, in preparation of the GAIACornerstone mission by ESA, by which the Ca ii IRT spectral range willbe spectroscopically observed for millions of stars. Methods: The{R_IRT} index is calculated for each observed star as the differencebetween the calculated NLTE photospheric central intensity and theobserved one. The residual EQW, {Δ W_IRT}, is calculated as thearea of the positive profile obtained as the difference between thecalculated NLTE photospheric and the observed profiles. We correlate{log{R'_HK}} with {R_IRT} and the {Δ W_IRT}. Results: Thisanalysis indicates that Ca ii IRT lines are good chromosphericdiagnostics. We find that both {Δ W_IRT} and the {R_IRT}quantities can be used as chromospheric indicators, although the formerexhibits a tighter correlation with the {log{R'_HK}} index. Furthermore,we find that the total chromospheric excess EQW in the Ca ii IRT isalmost linearly correlated with the excess in the Ca ii H & Kdoublet, as estimated through the {log{R'_HK}} index.Based on observations made with the Italian Telescopio Nazionale Galileo(TNG) operated on the island of La Palma by the Centro Galileo Galileiof the Consorzio Nazionale per l'Astronomia e l'Astrofisica at theSpanish Observatorio del Roque de los Muchachos of the Instituto deAstrofísica de Canarias. Table 4 is only available in electronicform at http://www.aanda.org
| 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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Observation and Astrometry data
| Constellation: | へび座 |
| Right ascension: | 18h08m08.64s |
| Declination: | -07°07'11.7" |
| Apparent magnitude: | 7.526 |
| Distance: | 147.275 parsecs |
| Proper motion RA: | -15.5 |
| Proper motion Dec: | -5.4 |
| B-T magnitude: | 9.079 |
| V-T magnitude: | 7.655 |
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