  [Context]. Blue stragglers are easy to identify in globular clusters, but are
much harder to identify in the field. Here we present the serendipitous
discovery of one field blue straggler, HIP 10725, that closely matches the Sun
in mass and age, but with a metallicity slightly lower than the Sun's.
[Methods]. We employ high resolution (R $\sim 10^5$) high S/N (330) VLT/UVES
spectra to perform a differential abundance analysis of the solar analogue HIP
10725. Radial velocities obtained by other instruments were also used to check
for binarity. We also study its chromospheric activity, age and rotational
velocity. [Results]. We find that HIP 10725 is severely depleted in beryllium
([Be/H] <= -1.2 dex) for its stellar parameters and age. The abundances
relative to solar of the elements with Z <= 30 show a correlation with
condensation temperature and the neutron capture elements produced by the
s-process are greatly enhanced, while the r-process elements seem normal. We
found its projected rotational velocity (v sin i = 3.3+/-0.1 km/s) to be
significantly larger than solar, and incompatible with its isochrone-derived
age. Radial velocity monitoring shows that the star has a binary companion.
[Conclusions]. Based on the high s-process element enhancements and low
beryllium abundance, we suggest that HIP 10725 has been polluted by
mass-transfer from an AGB star, probably with initial mass of about 2 M_Sun.
The radial velocity variations suggest the presence of an unseen binary
companion, probably the remnant of a former AGB star. Isochrones predict a
solar-age star, but this is in disagreement with the high projected rotational
velocity and high chromospheric activity. We conclude that HIP 10725 is a field
blue straggler, rejuvenated by the mass transfer process of its former AGB
companion.
