  Spectro-seismic measurements of red giants enabled the recent discovery of
stars in the thick disk that are more massive than 1.4 M_sun. While it has been
claimed that most of these stars are younger than the rest of the typical thick
disk stars, we show evidence that they might be products of mass transfer in
binary evolution, notably evolved blue stragglers. We took new measurements of
the radial velocities in a sample of 26 stars from APOKASC, including 13
"young" stars and 13 "old" stars with similar stellar parameters but with
masses below 1.2 M_sun and found that more of the "young" stars appear to be in
binary systems with respect to the "old" stars. Furthermore, we show that the
"young" stars do not follow the expected trend of [C/H] ratios versus mass for
individual stars. However, with a population synthesis of low-mass stars
including binary evolution and mass transfer, we can reproduce the observed
[C/N] ratios versus mass. Our study shows how asteroseismology of solar-type
red giants provides us with a unique opportunity to study the evolution of
field blue stragglers after they have left the main-sequence.
