N. Rea, G. L. Israel, P. Esposito, J. A. Pons, A. Camero-Arranz, R. P. Mignani, R. Turolla, S. Zane, M. Burgay, A. Possenti, S. Campana, T. Enoto, N. Gehrels, E. Gogus, D. Gotz, C. Kouveliotou, K. Makishima, S. Mereghetti, S. R. Oates, D. M. Palmer, R. Perna, L. Stella, A. Tiengo
We report on the long term X-ray monitoring with Swift, RXTE, Suzaku and XMM-Newton of the outburst of the recently discovered magnetar Swift J1822.3-1606 (SGR 1822-1606), from the first observations soon after the detection of the short X-ray bursts which led to its discovery, through the first stages of its outburst decay (covering the time-span from July 2011, until end of February 2012). We also report on archival ROSAT observations which witnessed the source during its likely quiescent state, and on Swift J1822.3-1606's upper limits on radio-pulsed and optical emission during outburst, with the Green Bank Telescope (GBT) and the Gran Telescopio Canarias (GTC), respectively. Our X-ray timing analysis finds the source rotating with a period of P=8.43772013(2)s and a period derivative \dot{P}=9.1(4)x10^{-14} s/s, which entails an inferred dipolar surface magnetic field of B=2.8x10^{13} G at the equator. This measurement makes Swift J1822.3-1606 the second magnetar with a dipolar magnetic field lower than the electron critical field (after SGR 0418+5729; Rea et al. 2010). Following the flux and spectral evolution from the beginning of the outburst until now, 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 toroidal surface fields of B_{p} ~ 2x10^{14} G and B_{tor}~10^{16} G, respectively, and if its current age is ~0.5 Myr.
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http://arxiv.org/abs/1203.6449
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