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arXiv · 1510.09157

The Outburst Decay of the Low Magnetic Field Magnetar SWIFT J1822.3-1606: Phase-resolved Analysis and Evidence for a Variable Cyclotron Feature

Guillermo A. Rodríguez Castillo·Gian Luca Israel·Andrea Tiengo·David Salvetti·Roberto Turolla·Silvia Zane·Nanda Rea·Paolo Esposito·Sandro Mereghetti·Rosalba Perna·Luigi Stella·José A. Pons·Sergio Campana·Diego Götz·Sara Motta
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Abstract

We study the timing and spectral properties of the low-magnetic field, transient magnetar SWIFT J1822.3-1606 as it approached quiescence. We coherently phase-connect the observations over a time-span of ~500 days since the discovery of SWIFT J1822.3-1606 following the Swift-BAT trigger on 2011 July 14, and carried out a detailed pulse phase spectroscopy along the outburst decay. We follow the spectral evolution of different pulse phase intervals and find a phase and energy-variable spectral feature, which we interpret as proton cyclotron resonant scattering of soft photon from currents circulating in a strong (10^14 G) small-scale component of the magnetic field near the neutron star surface, superimposed to the much weaker (~3 x 10^13 G) magnetic dipole field. We discuss also the implications of the pulse-resolved spectral analysis for the emission regions on the surface of the cooling magnetar.

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Guillermo A. Rodríguez Castillo, Gian Luca Israel, Andrea Tiengo, David Salvetti, Roberto Turolla, Silvia Zane, Nanda Rea, Paolo Esposito, Sandro Mereghetti, Rosalba Perna, Luigi Stella, José A. Pons, Sergio Campana, Diego Götz, Sara Motta. 2015-10-30. The Outburst Decay of the Low Magnetic Field Magnetar SWIFT J1822.3-1606: Phase-resolved Analysis and Evidence for a Variable Cyclotron Feature. https://doi.org/10.1093/mnras%2Fstv2490

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