  We present a re-analysis of 47 Rossi X-ray Timing Explorer observations of
the 11Hz accreting pulsar IGR J17480-2446 in Terzan 5 during its 2010 outburst.
We studied the fast-time variability properties of the source and searched for
quasi-periodic oscillations (QPOs) in a large frequency range. General
Relativity predicts that frame-dragging occurs in the vicinity of a spinning
compact object and induces the precession of matter orbiting said object. The
relativistic precession model predicts that this frame-dragging can be observed
as QPOs with a characteristic frequency in the light curves of accreting
compact objects. Such QPOs have historically been classified as horizontal
branch oscillations in neutron star systems, and for a neutron star spinning at
11 Hz these oscillations are expected at frequencies below 1 Hz. However,
previous studies of IGR J17480-2446 have classified QPOs at 35-50 Hz as
horizontal branch oscillations, thus casting doubts on the frame-dragging
nature of such QPOs. Here we report the detection of seven very low-frequency
QPOs, previously undetected, with centroid frequencies below 0.3 Hz, and which
can be ascribed to frame-dragging. We also discuss the possible nature of the
QPOs detected at 35-50 Hz in this alternative scenario.
