  We report on the long term X-ray monitoring with Swift, RXTE, Suzaku,
Chandra, and XMM-Newton of the outburst of the newly discovered magnetar Swift
J1822.3-1606 (SGR 182-1606), from the first observations soon after the
detection of the short X-ray bursts which led to its discovery (July 2011),
through the first stages of its outburst decay (April 2012). Our X-ray timing
analysis finds the source rotating with a period of P = 8.43772016(2) s and a
period derivative Pdot = 8.3(2) x 10e-14 s s-1, which entails an inferred
dipolar surface magnetic field of 2.7 x 10e13 G at the equator. This
measurement makes Swift J1822.3-1606 the second lowest magnetic field magnetar
(after SGR 0418+5729; Rea et al. 2010). Following the flux and spectral
evolution from the beginning of the outburst, we find that the flux decreased
by about an order of magnitude, with a subtle softening of the spectrum, both
typical of the outburst decay of magnetars. By modeling the secular thermal
evolution of Swift J1822.3+1606, we find that the observed timing properties of
the source, as well as its quiescent X-ray luminosity, can be reproduced if it
was born with a poloidal and crustal toroidal fields of Bp ~ 1.5 x 10e14 G and
Btor ~ 7 x 10e14 G, respectively, and if its current age is ~550 kyr (more
details in Rea et al. 2012).
