Chromospheres in Metal-Poor Stars Evidenced from the He I 10830A Line

Abstract

Based on the near-IR spectra of 33 late-type stars in the wide metallicity range (mainly dwarfs and partly giants) obtained with IRCS+AO188 of the Subaru Telescope, we confirmed that He I 10830A line is seen in absorption in almost all moderately to extremely metal-poor stars of thick disk and halo population (from [Fe/H]~ -0.5 down to [Fe/H]~ -3.7), the strength of which is almost constant irrespective of the metallicity. This is an evidence that chromospheric activity at a basal level persists even for such old stars, despite that their rotations are considered to be slowed down and incapable of sustaining a dynamo, suggesting that some kind of chromospheric heating mechanism independent of rotation/magnetism (e.g., acoustic heating) may take place.

8 pages, 6 figures, Pub. Astron. Soc. Japan, Vol. 63 (2011), in press

References in corpus (3)

• Sun-as-a-Star Spectrum Variations 1974-2006
• An Overview of the Rotational Behavior of Metal--Poor Stars
• Exploring the [S/Fe] Behavior of Metal-Poor Stars with the S I 1.046 micron Lines

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