The Energy Spectrum of Anomalous X-ray Pulsars and Soft Gamma-ray Repeaters
arXiv:1004.3391 · doi:10.1051/0004-6361/200911834
Abstract
Assuming that AXPs and SGRs accrete matter from a fallback disk, we attempt to explain both the soft and the hard X-ray emission as the result of the accretion process. We also attempt to explain their radio emission or the lack of it. We test the hypothesis that the power-law, hard X-ray spectra are produced in the accretion flow mainly by bulk-motion Comptonization of soft photons emitted at the neutron star surface. Fallback disk models invoke surface dipole magnetic fields of G, which is what we assume here. Unlike normal X-ray pulsars, for which the accretion rate is highly super-Eddington, the accretion rate is approximately Eddington in AXPs and SGRs and thus the bulk-motion Comptonization operates efficiently. As an illustrative example we reproduce both the hard and the soft X-ray spectra of AXP 4U 0142+61 well using the XSPEC package compTB. Our model seems to explain both the hard and the soft X-ray spectra of AXPs and SGRs, as well as their radio emission or the lack of it, in a natural way. It might also explain the short bursts observed in these sources. On the other hand, it cannot explain the giant X-ray outbursts observed in SGRs, which may result from the conversion of magnetic energy in local multipole fields.
6 pages, 2 figures, minor corrections, accepted for publication in A&A
References in corpus (21)
- The strongest cosmic magnets: Soft Gamma-ray Repeaters and Anomalous X-ray Pulsars
- Transient pulsed radio emission from a magnetar
- Corona of Magnetars
- A Debris Disk Around An Isolated Young Neutron Star
- The Magnificent Seven: Magnetic fields and surface temperature distributions
- 1E 1547.0-5408: a radio-emitting magnetar with a rotation period of 2 seconds
- Discovery of luminous pulsed hard X-ray emission from anomalous X-ray pulsars 1RXS J1708-4009, 4U 0142+61 and 1E 2259+586 by INTEGRAL and RXTE
- Resonant Compton Upscattering in Anomalous X-ray Pulsars
- Detailed high-energy characteristics of AXP 4U 0142+61 - Multi-year observations with INTEGRAL, RXTE, XMM-Newton and ASCA
- Average hard X-ray emission from NS LMXBs: Observational evidence of different spectral states in NS LMXBs
- Recent Progress on Anomalous X-ray Pulsars
- Detailed high-energy characteristics of AXP 1RXS J170849-400910 - Probing the magnetosphere using INTEGRAL, RXTE and XMM-Newton
- A new Comptonization model for low-magnetized accreting neutron stars in low mass X-ray binaries
- Anomalous X-ray pulsars: Persistent States with Fallback Disks
- Exciting the Magnetosphere of the Magnetar CXOU J164710.2-455216 in Westerlund 1
- On the evolution of anomalous X-ray pulsars and soft gamma ray repeaters with fallback disks
- A Mid-Infrared Counterpart to the Magnetar 1E 2259+586
- XMM-Newton observation of the Soft Gamma Ray Repeater SGR 1627-41 in a low luminosity state
- QPO emission from moving hot spots on the surface of neutron stars: a model
- On the X-Ray Light Curve, Pulsed-Radio Emission, and Spin Frequency Evolution of the Transient Anomalous X-Ray Pulsar Xte J1810--197 During its X-Ray Outburst
- QED can explain the non-thermal emission from SGRs and AXPs : Variability
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