We investigate the X-ray enhancement and the long-term evolution of the recently discovered , second “ low-B magnetar ” Swift J1822.3–1606 in the frame of the fallback disk model .
During a soft gamma burst episode , the inner disk matter is pushed back to larger radii forming a density gradient at the inner disk .
Subsequent relaxation of the inner disk could account for the observed X-ray enhancement light curve of Swift J1822.3–1606 .
We obtain model fits to the X-ray data with basic disk parameters similar to those employed to explain the X-ray outburst light curves of other anomalous X-ray pulsars and soft gamma repeaters .
The long period ( 8.4 s ) of the neutron star can be reached by the effect of the disk torques in the long-term accretion phase ( 1 - 3 \times 10 ^ { 5 } yr ) .
The currently ongoing X-ray enhancement could be due to a transient accretion epoch or the source could still be in the accretion phase in quiescence .
Considering these different possibilities , we determine the model curves that could represent the long-term rotational and the X-ray luminosity evolution of Swift J1822.3–1606 , which constrain the strength of the magnetic dipole field to the range of 1 - 2 \times 10 ^ { 12 } G on the surface of the neutron star .