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Hα and the Ca II H and K lines as activity proxies for late-type stars
Context: The main chromospheric activity indicator is the S index, whichis the ratio of the flux in the core of the Ca II H and K lines to thecontinuum nearby, and is well studied for stars from F to K. Anotherchromospheric proxy is the Hα line, which is believed to betightly correlated with the Ca II index. Aims: In this work wecharacterize both chromospheric activity indicators, the one associatedwith the H and K Ca II lines and the other with Hα, for the wholerange of late type stars, from F to M. Methods: We present periodicmedium-resolution echelle observations covering the complete visualrange, taken at the CASLEO Argentinean Observatory over 7 years. We usea total of 917 flux-calibrated spectra for 109 stars that range from F6to M5. We statistically study these two indicators for stars ofdifferent activity levels and spectral types. Results: We directlyderive the conversion factor that translates the known S index to fluxin the Ca II cores, and extend its calibration to a wider spectralrange. We investigate the relation between the activity measurements inthe calcium and hydrogen lines, and found that the usual correlationobserved is the product of the dependence of each flux on stellarcolour, and not the product of similar activity phenomena.Tables 1 and 2 and full Figs. 1 and 6 are only available in electronicform at http://www.aanda.org
| Library of flux-calibrated echelle spectra of southern late-type dwarfs with different activity levels
We present Echelle spectra of 91 late-type dwarfs, of spectral typesfrom F to M and of different levels of chromospheric activity, obtainedwith the 2.15 m telescope of the CASLEO Observatory located in theArgentinean Andes. Our observations range from 3890 to 6690 Å, ata spectral resolution from 0.141 to 0.249 Å per pixel(R=λ/δ λ ≈ 26 400). The observations were fluxcalibrated with the aid of long slit spectra. A version of thecalibrated spectra is available via the World Wide Web.Table 2 is also available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/414/699The spectra are available as FITS and ascii-files at the URL:http://www.iafe.uba.ar/cincunegui/spectra/Table2.html. They are alsoavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/414/699. When convertingthe fits to ascii, the spectra were oversampled to a constant δλ ≈ 0.15 Å.Table 2 is also available in electronic form at the CDS via anonymous
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Osservazione e dati astrometrici
| Costellazione: | Scorpione |
| Ascensione retta: | 17h18m58.25s |
| Declinazione: | -32°57'55.8" |
| Magnitudine apparente: | 7.864 |
| Distanza: | 10000000 parsec |
| Moto proprio RA: | 1.9 |
| Moto proprio Dec: | -2.9 |
| B-T magnitude: | 10.283 |
| V-T magnitude: | 8.064 |
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