High-resolution spectra of very low-mass stars |
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| Authors: | C G Tinney & I N Reid |
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| Institution: | Anglo-Australian Observatory, PO Box 296, Epping, NSW 2121, Australia,;European Southern Observatory, Garching, Germany,;Palomar Observatory, 105-24, California Institute of Technology, Pasadena, CA 91125, USA |
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| Abstract: | We present the results of high-resolution (1–0.4 ?) optical spectroscopy of a sample of very low-mass stars. These data are used to examine the kinematics of the stars at the bottom of the hydrogen-burning main sequence. No evidence is found for a significant difference between the kinematics of the stars in our sample with I ? K > 3.5 ( M bol ? 12.8) and those of more massive M dwarfs ( M bol ≈ 7–10). A spectral atlas at high (0.4-?) resolution for M8–M9+ stars is provided, and the equivalent widths of Cs I , Rb I and Hα lines present in our spectra are examined. We analyse our data to search for the presence of rapid rotation, and find that the brown dwarf LP 944-20 is a member of the class of 'inactive, rapid rotators'. Such objects seem to be common at and below the hydrogen-burning main sequence. It seems that in low-mass/low-temperature dwarf objects either the mechanism that heats the chromosphere, or the mechanism that generates magnetic fields, is greatly suppressed. |
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| Keywords: | techniques: radial velocities stars: activity stars: chromospheres stars: kinematics stars: low-mass brown dwarfs stars: rotation |
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