The low mass X-ray binary (LMXB) IGR J17480-2446 is an 11 Hz accreting pulsar located in the core of the globular cluster Terzan 5. This is a mildly recycled accreting pulsar with a peculiar evolutionary history since its total age has been suggested to be less than a few hundred Myr, despite the very old age of Terzan 5 (~12 Gyr). Solving the origin of this age discrepancy might be very valuable because it can reveal why systems like IGR J17480-2446 are so rare in our Galaxy. We have performed numerical simulations (dynamical and binary evolution) to constrain the evolutionary history of IGR J17480-2446 . We find that the binary has a high probability to be the result of close encounters, with a formation mechanism compatible with the tidal capture of the donor star. The result reinforces the hypothesis that IGR J17480-2446 is a binary that started mass transfer in an exceptionally recent time. We also show that primordial interacting binaries in the core of Terzan 5 are strongly affected by a few hundred close encounters (fly-by) during their lifetime. This effect might delay, accelerate or even interrupt the Roche lobe overflow (RLOF) phase. Our calculations show that systems of this kind can form exclusively in dense environments like globular clusters.
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