  Using a population synthesis technique, we have calculated detailed models of
the present-day field population of objects that have resulted from the merger
of a giant primary and a main-sequence or brown dwarf secondary during
common-envelope evolution. We used a grid of 116 stellar and 32 low-mass/brown
dwarf models, a crude model of the merger process, and followed the angular
momentum evolution of the binary orbit and the primary's rotation prior to
merger, as well as the merged object's rotation after the merger. We find that
present-day merged objects that are observable as giant stars or core-helium
burning stars in our model population constitute between 0.24% and 0.33% of the
initial population of ZAMS binaries, depending upon the input parameters
chosen. The median projected rotational velocity of these merged objects is ~16
km/sec, an order of magnitude higher than the median projected rotational
velocity in a model population of normal single stars calculated using the same
stellar models and initial mass function. The masses of the merged objects are
typically less than ~2 solar masses, with a median mass of 1.28 solar masses,
which is slightly more than, but not significantly different from, their normal
single star counterparts. The luminosities in our merged object population
range from ~10-100 solar luminosities, with a strong peak in the luminosity
distribution at ~60 solar luminosities, since the majority of the merged
objects (57%) lie on the horizontal branch at the present epoch. The results of
our population synthesis study are discussed in terms of possible observational
counterparts either directly involving the high rotational velocity of the
merger product or indirectly, via the effect of rotation on envelope abundances
and on the amount and distribution of circumstellar matter.
