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

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.

Accepted for publication in MNRAS

References in corpus (3)

• The strongest cosmic magnets: Soft Gamma-ray Repeaters and Anomalous X-ray Pulsars
• Untwisting magnetospheres of neutron stars
• Pulse Phase-coherent Timing and Spectroscopy of CXOU J164710.2-45521 Outbursts

Cited by in corpus (36)

• Magnetars
• Systematic study of magnetar outbursts
• Magnetic field evolution in magnetar crusts through three dimensional simulations
• The NICER View of the 2020 Burst Storm and Persistent Emission of SGR 1935+2154
• Magnetars: a short review and some sparse considerations
• Magnetic Field Evolution of Neutron Stars I: Basic formalism, numerical techniques, and first results
• An emission state switching radio transient with a 54 minute period
• A global model of the magnetorotational instability in protoneutron stars
• MRI-driven $\alpha -\Omega$ dynamos in protoneutron stars
• Narrow phase-dependent features in X-ray Dim Isolated Neutron Stars: a new detection and upper limits
• A new scenario for magnetar formation: Tayler-Spruit dynamo in a proto-neutron star spun up by fallback
• Physics and astrophysics of strong magnetic field systems with eXTP
• The variable spin-down rate of the transient magnetar XTE J1810--197
• Millisecond Magnetars
• A deep XMM-Newton look on the thermally emitting isolated neutron star RX J1605.3+3249
• A NuSTAR confirmation of the 36 ks hard X-ray pulse-phase modulation in the magnetar 1E 1547.0$-$5408
• The life cycle of magnetars: a novel approach to estimate their ages
• Quasi-universality of the magnetic deformation of neutron stars in general relativity and beyond
• Universal detection of high-temperature emission in X-ray Isolated Neutron Stars
• Strongly magnetized pulsars: explosive events and evolution
• Detailed X-ray spectroscopy of the magnetar 1E 2259+586
• Tayler-Spruit dynamo in stably stratified rotating fluids: Application to proto-magnetars
• Classification of pulsars with Dirichlet process Gaussian mixture model
• GRB 171205A: Hypernova and Newborn Neutron Star
• Heating in Magnetar Crusts from Electron Captures
• Three-Dimensional Magnetothermal Simulations of Magnetar Outbursts
• Resolving dichotomy in compact objects through continuous gravitational waves observation
• Investigation of the High-Energy Emission from the Magnetar-like Pulsar PSR J1119-6127 after the 2016 Outburst
• Universality of gravitational radiation from magnetar magnetospheres
• XMM-Newton observations of PSR J0554+3107: pulsing thermal emission from a cooling high-mass neutron star
• Matched-filtering Line Search Methods Applied to Suzaku Data
• Geometrical envelopes of fast radio bursts
• Evidence of the association of repeating fast-radio-burst sources with fast-spinning super-twisted magnetars
• Turbulence in Magnetised Neutron Stars
• AstroSat observation of the magnetar SGR J1830$-$0645 during its first detected X-ray outburst
• Correlation of Burst Behaviour with Magnetar Age