  We report the discovery that the pre-main sequence object LkCa3 in the
Taurus-Auriga star-forming region is a hierarchical quadruple system of M
stars. It was previously known to be a close (~0.5 arc sec) visual pair, with
one component being a moderately eccentric 12.94-day single-lined spectroscopic
binary. A re-analysis of archival optical spectra complemented with new
near-infrared spectroscopy shows both visual components to be double-lined, the
second one having a period of 4.06 days and a circular orbit. In addition to
the orbital elements, we determine optical and near-infrared flux ratios,
effective temperatures, and projected rotational velocities for all four stars.
Using existing photometric monitoring observations of the system that had
previously revealed the rotational period of the primary in the longer-period
binary, we detect also the rotational signal of the primary in the 4.06-day
binary, which is synchronized with the orbital motion. With only the assumption
of coevality, a comparison of all of these constraints with current stellar
evolution models from the Dartmouth series points to an age of 1.4 Myr and a
distance of 133 pc, consistent with previous estimates for the region and
suggesting the system is on the near side of the Taurus complex. Similar
comparisons of the properties of LkCa3 and of the well-known quadruple pre-main
sequence system GG Tau with the widely used models from the Lyon series for a
mixing length parameter of alpha_ML = 1.0 strongly favor the Dartmouth models.
