Chromospheric Activity in Metal-Poor Dwarfs

Ruth C. Peterson; Carolus J. Schrijver

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arXiv · astro-ph/0005367

Chromospheric Activity in Metal-Poor Dwarfs

Ruth C. Peterson·Carolus J. Schrijver

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Abstract

We have obtained echelle spectra with the Hubble Space Telescope (HST) of the MgII 2800A region of ten stars whose metallicities range from 1/300 to 1/3 that of the Sun, and whose space velocities suggest a halo or old thick-disk origin. Spectra of all ten show double-peaked emission in the MgII core, very much like the quiet Sun. A half-dozen non-rotating stars were observed more than once, and show at most a low level of variability in the emission flux, comparable to that of quiet stars of solar metallicity. For four stars, we have obtained Lyman-alpha spectra at 0.2A resolution; all four show emission. The data thus strongly suggest that chromospheric activity at a minimum level is present in all stars of near-solar temperature, regardless of age or metallicity. While this points to non-magnetic sources such as acoustic waves, a contribution from globally-organized magnetic fields is possible at a low level. We plan a longer series of MgII and Lyman alpha observations to constrain this.

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Ruth C. Peterson, Carolus J. Schrijver. 2000-05-18. Chromospheric Activity in Metal-Poor Dwarfs. https://arxiv.org/abs/astro-ph/0005367

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