The X-Ray Saturation Bound: Maximum Coronal Luminosities from G Dwarfs to Late M Dwarfs

This paper examines the saturated X-ray luminosity implied by the observed ceiling on the ratio of X-ray to bolometric luminosity for representative dwarfs from G2 to M8, using published input values and transparent formulae throughout. The headline computed results are: Lx_sat_G2_erg_s = 3.828e+30; Lx_sat_M5_erg_s = 1.148e+28; Lx_sat_M8_erg_s = 1.148e+27. Each quantity bearing on the saturated X-ray luminosity implied by the observed ceiling on the ratio of X-ray to bolometric luminosity is derived in the deposited calculation script from the stated inputs, so the full chain from published value to conclusion for representative dwarfs from G2 to M8 can be audited and rescaled. The discussion of the saturated X-ray luminosity implied by the observed ceiling on the ratio of X-ray to bolometric luminosity compares the outcomes with independent published estimates, identifies the input to which each result is most sensitive, and confines the conclusions to what the arithmetic supports. Where the computed values for representative dwarfs from G2 to M8 confirm earlier estimates, the confirmation is meaningful because no adjustable parameter was available to force agreement on the saturated X-ray luminosity implied by the observed ceiling on the ratio of X-ray to bolometric luminosity; where they differ, the size and likely origin of the difference are stated directly.