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(abridged) We analyse the spectral and pulse properties of the 11 Hztransient accreting pulsar, IGR J17480-2446, in the globular cluster Terzan 5,considering all the available RXTE, Swift and INTEGRAL observations performedbetween October and November, 2010.  By measuring the pulse phase evolution we conclude that the NS spun up at anaverage rate of <nu_dot>=1.48(2)E-12 Hz/s, compatible with the accretion of theKeplerian angular momentum of matter at the inner disc boundary. Similar toother accreting pulsars, the stability of the pulse phases determined by usingthe second harmonic component is higher than that of the phases based on thefundamental frequency. Under the assumption that the second harmonic is a goodtracer of the neutron star spin frequency, we successfully model its evolutionin terms of a luminosity dependent accretion torque. If the NS accretes thespecific Keplerian angular momentum of the in-flowing matter, we estimate theinner disc radius to lie between 47 and 93 km when the luminosity attains itspeak value. Smaller values are obtained if the interaction between the magneticfield lines and the plasma in the disc is considered.  The phase-averaged spectrum is described by thermal Comptonization of photonswith energy of ~1 keV. A hard to soft state transition is observed during theoutburst rise. The Comptonized spectrum evolves from a Comptonizing cloud at anelectron temperature of ~20 keV towards an optically denser cloud at kT_e~3keV. At the same time, the pulse amplitude decreases from 27% to few per centand becomes strongly energy dependent. We discuss various possibilities toexplain such a behaviour, proposing that at large accretion luminosities asignificant fraction of the in-falling matter is not channelled towards themagnetic poles, but rather accretes more evenly onto the NS surface.

The pulse profile and spin evolution of the accreting pulsar in Terzan 5, IGR J17480-2446, during its 2010 outburst