English

X-ray Emission From Nearby M-dwarfs: the Super-saturation Phenomenon

Astrophysics 2009-10-31 v1

Abstract

A rotation rate and X-ray luminosity analysis is presented for rapidly rotating single and binary M-dwarf systems. X-ray luminosities for the majority of both single & binary M-dwarf systems with periods below 56\simeq 5-6 days (equatorial velocities, Veq>_{eq}> 6 km~s1^{-1}) are consistent with the current rotation-activity paradigm, and appear to saturate at about 10310^{-3} of the stellar bolometric luminosity. The single M-dwarf data show tentative evidence for the super-saturation phenomenon observed in some ultra-fast rotating (>> 100 km~s1^{-1}) G & K-dwarfs in the IC 2391, IC 2602 and Alpha Persei clusters. The IC 2391 M star VXR60b is the least X-ray active and most rapidly rotating of the short period (Prot<_{rot}< 2 days) stars considered herein, with a period of 0.212 days and an X-ray activity level about 1.5 sigma below the mean X-ray emission level for most of the single M-dwarf sample. For this star, and possibly one other, we cautiously believe that we have identified the first evidence of super-saturation in M-dwarfs. If we are wrong, we demonstrate that only M-dwarfs rotating close to their break up velocities are likely to exhibit the super-saturation effect at X-ray wavelengths.

Keywords

Cite

@article{arxiv.astro-ph/0007159,
  title  = {X-ray Emission From Nearby M-dwarfs: the Super-saturation Phenomenon},
  author = {David J James and Moira M Jardine and Robin D Jeffries and Sofia Randich and Andrew Collier Cameron and Miguel Ferreira},
  journal= {arXiv preprint arXiv:astro-ph/0007159},
  year   = {2009}
}

Comments

12 pages, 4 figures, accepted by MNRAS