IAFE   05512
INSTITUTO DE ASTRONOMIA Y FISICA DEL ESPACIO
Unidad Ejecutora - UE
artículos
Título:
Hα and the Ca II H and K lines as activity proxies for late-type stars
Autor/es:
CINCUNEGUI, C. C.; DÍAZ, R. F.; MAUAS, P.J.D.
Revista:
ASTRONOMY AND ASTROPHYSICS
Editorial:
EDP
Referencias:
Lugar: Paris; Año: 2007 vol. 469 p. 309 - 317
ISSN:
0004-6361
Resumen:
Context: The main chromospheric activity indicator is the S index, which
is the ratio of the flux in the core of the Ca II H and K lines to the
continuum nearby, and is well studied for stars from F to K. Another
chromospheric proxy is the Hα line, which is believed to be
tightly correlated with the Ca II index. Aims: In this work we
characterize both chromospheric activity indicators, the one associated
with the H and K Ca II lines and the other with Hα, for the whole
range of late type stars, from F to M. Methods: We present periodic
medium-resolution echelle observations covering the complete visual
range, taken at the CASLEO Argentinean Observatory over 7 years. We use
a total of 917 flux-calibrated spectra for 109 stars that range from F6
to M5. We statistically study these two indicators for stars of
different activity levels and spectral types. Results: We directly
derive the conversion factor that translates the known S index to flux
in the Ca II cores, and extend its calibration to a wider spectral
range. We investigate the relation between the activity measurements in
the calcium and hydrogen lines, and found that the usual correlation
observed is the product of the dependence of each flux on stellar
colour, and not the product of similar activity phenomena.