Flux-flux relation : MG II H and K versus X-rays in dwarf M and K stars.

Abstract

Surface X-ray and Mg II h and k fluxes are presented for a group of dMe, dKe, dM, and dK stars. No correlation is apparent between the fluxes for the group of stars as a whole, although a good correlation is present for a subgroup, i.e., the dMe/dKe's. The Mg II and X-ray luminosities for these active stars define an upper boundary, which is dependent upon the stellar radii. The Mg II luminosity from the less active dM/dK stars are also radii-dependent, but this is not the case for the X-ray luminosity. This may indicate a difference in the heating mechanisms for the chromosphere and corona, with acoustic wave heating being an important contributor in the chromosphere and/or a difference in the plage filling factors in the two regions.