Coevality and Mass Ratios

The value on the x-axis, delta logLsec, refers to the amount in log L that the secondary must move to make it the same age as the primary for the two sets of pre-main-sequence evolutionary tracks indicated. There is a tendancy for secondaries to be younger than their primaries in some cases. Objects where the primaries and secondaries have nearly the same mass are plotted toward the bottom of the figures.