Aql X-1 is the most prolific low mass X–ray binary transient hosting a neutron star .
In this paper we focus on the return to quiescence following the 2010 outburst of the source .
This decay was monitored thanks to 11 pointed observations taken with XMM-Newton , Chandra and Swift .
The decay from outburst to quiescence is very fast , with an exponential decay characteristic time scale of \sim 2 d. Once in quiescence the X–ray flux of Aql X-1 remained constant , with no further signs of variability or decay .
The comparison with the only other well-monitored outburst from Aql X-1 ( 1997 ) is tail-telling .
The luminosities at which the fast decay starts are fully compatible for the two outbursts , hinting at a mechanism intrinsic to the system and possibly related to the neutron star rotation and magnetic field ( i.e. , the propeller effect ) .
In addition , for both outbursts , the decay profiles are also very similar , likely resulting from the shut-off of the accretion process onto the neutron star surface .
Finally , the quiescent neutron star temperatures at the end of the outbursts are well consistent with one another , suggesting a hot neutron star core dominating the thermal balance .
Small differences in the quiescent X–ray luminosity among the two outbursts can be attributed to a different level of the power law component .