  The Swift satellite monitored the quiescence of the low-mass X-ray binary
transient Aql X-1 on a weekly basis during the March-November 2012 interval. A
total of 42 observations were carried out in the soft X-ray (0.3-10 keV) band
with the X-ray Telescope on board Swift. We investigated the X-ray variability
properties of Aql X-1 during quiescence by tracking luminosity variations and
characterising them with a detailed spectral analysis. The source is highly
variable in this phase and two bright flares were detected, with peak
luminosities of ~4x10^{34} erg s^{-1} (0.3-10 keV). Quiescent X-ray spectra
require both a soft thermal component below ~2 keV and a hard component (a
power law tail) above ~2 keV. Changes in the power law normalisation alone can
account for the overall observed variability. Therefore, based on our data set,
the quiescent X-ray emission of Aql X-1 is consistent with the cooling of the
neutron star core and with mechanisms involving the accretion of matter onto
the neutron star surface or magnetosphere.
