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arXiv · 0901.1860

The "Living with a Red Dwarf" Program

Edward F. Guinan·Scott G. Engle
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Abstract

Red Dwarfs (main-sequence / dwarf M or dM) stars are the most common stars in the Galaxy. These cool, faint, low mass stars comprise over 75% of all stars. Because of their low luminosities (~0.0008-0.06 of the Sun's luminosity), the circumstellar habitable zones (HZs) of dM stars are located within ~0.05-0.4 AU of the host star. Nevertheless, the prospect of life on a planet located within the HZ of a red dwarf is moderately high, based on the longevity of these stars (>50 Gyr), their constant luminosities and high space densities. Here we describe the aims and early results of the "Living with a Red Dwarf" Program - a study of dM stars that we have been carrying out over the last few years. The primary focus of our research on dM stars is the study of their magnetic dynamos and resulting star spots & coronal X-ray and chromospheric UV emissions as a function of age, rotation and spectral type. This program will provide datasets that can be used as inputs for the study of all aspects of dM stars, along with the planets already discovered hosted by them and the probable hundreds (thousands?) of planets expected to be uncovered in the near future by missions such as Kepler & Darwin/TPF. These datasets will be invaluable to those who model exo-planetary atmospheres, as well as exobiologists & astrobiologists who are studying the possibilities of life elsewhere in the universe. A significant element of our program is the determination of accurate stellar magnetic-driven X-ray-UV (X-UV) irradiances that are generated by the dM stars' vigorous magnetic dynamos. These X-UV irradiances (and flare frequencies) are strongly dependent on rotation, and thus age, and diminish as the stars lose angular momentum and spin-down over time via magnetic braking.

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Edward F. Guinan, Scott G. Engle. 2009-01-13. The "Living with a Red Dwarf" Program. https://arxiv.org/abs/0901.1860

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