  The low mass X-ray binary (LMXB) IGR J17480-2446 in the globular cluster
Terzan 5 harbors an 11 Hz accreting pulsar. This is the first object discovered
in a globular cluster with a pulsar spinning at such low rate. The accreting
pulsar is anomalous because its characteristics are very different from the
other five known slow accreting pulsars in galactic LMXBs. Many features of the
11 Hz pulsar are instead very similar to those of accreting millisecond
pulsars, spinning at frequencies >100 Hz. Understanding this anomaly is
valuable because IGR J17480-2446 can be the only accreting pulsar discovered so
far which is in the process of becoming an accreting millisecond pulsar. We
first verify that the neutron star (NS) in IGR J17480-2446 is indeed spinning
up by carefully analyzing X-ray data with coherent timing techniques that
account for the presence of timing noise. We then study the present Roche lobe
overflow epoch and the two previous spin-down epochs dominated by magneto
dipole radiation and stellar wind accretion. We find that IGR J17480-2446 is
very likely a mildly recycled pulsar and suggest that it has started a spin-up
phase in an exceptionally recent time, that has lasted less than a few 10^7 yr.
We also find that the total age of the binary is surprisingly low (<10^8 yr)
when considering typical parameters for the newborn NS and propose different
scenarios to explain this anomaly.
