Magnetic Inflation and Stellar Mass. V. Intensification and Saturation of M-dwarf Absorption Lines with Rossby Number

  • Muirhead P
  • Veyette M
  • Newton E
  • et al.
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Abstract

In young Sun-like stars and field M-dwarf stars, chromospheric and coronal magnetic activity indicators such as H α , X-ray, and radio emission are known to saturate with low Rossby number (Ro ≲ 0.1), defined as the ratio of rotation period to convective turnover time. The mechanism for the saturation is unclear. In this paper, we use photospheric Ti i and Ca i absorption lines in the Y band to investigate magnetic field strength in M dwarfs for Rossby numbers between 0.01 and 1.0. The equivalent widths of the lines are magnetically enhanced by photospheric spots, a global field, or a combination of the two. The equivalent widths behave qualitatively similar to the chromospheric and coronal indicators: we see increasing equivalent widths (increasing absorption) with decreasing Ro and saturation of the equivalent widths for Ro ≲ 0.1. The majority of M dwarfs in this study are fully convective. The results add to mounting evidence that the magnetic saturation mechanism occurs at or beneath the stellar photosphere.

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APA

Muirhead, P. S., Veyette, M. J., Newton, E. R., Theissen, C. A., & Mann, A. W. (2020). Magnetic Inflation and Stellar Mass. V. Intensification and Saturation of M-dwarf Absorption Lines with Rossby Number. The Astronomical Journal, 159(2), 52. https://doi.org/10.3847/1538-3881/ab5d3d

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