  We present ASCA X-ray observations of a sample of five groups selected from a
cross-correlation of the ROSAT All-Sky Survey with the White et al. optical
catalog of groups. These X-ray bright groups significantly increase the number
of known systems with temperatures between 2 and 3 keV. They have element
abundances of roughly 0.3 times solar that are typical of clusters, but their
favored ratio of Si/Fe abundance is lower than the cluster value. Combining the
ASCA results with ROSAT imaging data, we calculate total masses of a few to
several times 10^13 M_sun, gas mass fractions of ~10%, and baryonic mass
fractions of at least 15-20% within a radius of 0.5 Mpc. Upper limits for the
ratios of gas to galaxy mass and of the iron mass to galaxy luminosity overlap
with the range observed in rich clusters and extend to lower values, but not to
such low values as seen in much poorer groups. These results support the idea
that groups, unlike clusters, are subject to the loss of their primordial and
processed gas, and show that this transition occurs at the mass scale of the
2-3 keV groups. A discussion of ASCA calibration issues and a comparison of
ROSAT and ASCA temperatures are included in an Appendix.
