An Accretion Model for the Anomalous X-Ray Pulsar 4u 0142+61

Trümper, J.; Dennerl, K.; Kylafis, N. D.; Ertan, Ünal; Zezas, A.

doi:10.1088/0004-637x/764/1/49

Cited by 55 publications

(76 citation statements)

References 63 publications

(80 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The former possibility is ruled out because, for typical NS velocities and ISM densities, the resulting accretion rate is too small. Models invoking residual disks around isolated NSs are instead more plausible and represent the most widely discussed alternative to the magnetar interpretation [22,40,187]. In this class of models various mechanisms for the disk formation and different origins for the observed X-ray luminosity have been considered.…”

Section: Accretionmentioning

confidence: 99%

Pulsars and Magnetars

Mereghetti

2013

Braz J Phys

View full text Add to dashboard Cite

The high-energy sources known as anomalous X-ray pulsars (AXPs) and soft γ-ray repeaters (SGRs) are well explained as magnetars: isolated neutron stars powered by their own magnetic energy. After explaining why it is generally believed that the traditional energy sources at work in other neutron stars (accretion, rotation, residual heat) cannot power the emission of AXPs/SGRs, I review the observational properties of the twenty AXPs/SGRs currently known and describe the main features of the magnetar model. In the last part of this review I discuss the recent discovery of magnetars with low external dipole field and some of the relations between AXPs/SGRs and other classes of isolated neutron stars.

show abstract

Section: Accretionmentioning

confidence: 99%

Pulsars and Magnetars

Mereghetti

2013

Braz J Phys

View full text Add to dashboard Cite

show abstract

“…The apparent failure of the traditional energy reservoir of pulsars in SGR/AXPs has led to different scenarios for the explanation of SGRs and AXPs, e.g. : magnetars (Duncan & Thompson 1992;Thompson & Duncan 1995); drift waves near the light-cylinder of NSs (see Malov 2010, and references therein); fallback accretion onto NSs (Trümper et al 2013); accretion Article number, page 1 of 11 arXiv:1612.01875v1 [astro-ph.HE] 6 Dec 2016 A&A proofs: manuscript no. SGRsAXPs onto exotic compact stars such as quark stars (Xu et al 2006); the quark-nova remnant model (Ouyed et al 2011); and massive, fast rotating, highly magnetized WDs (Malheiro et al 2012;Boshkayev et al 2013;Rueda et al 2013;Coelho & Malheiro 2014) None of the above scenarios appears to be ruled out by the current observational data, thus further scrutiny of the nature and the possible energy reservoir of SGRs and AXPs deserves still attention.…”

Section: Introductionmentioning

confidence: 99%

The rotation-powered nature of some soft gamma-ray repeaters and anomalous X-ray pulsars

Coelho

Cáceres

Lima

et al. 2017

A&A

View full text Add to dashboard Cite

Context. Soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are slow rotating isolated pulsars whose energy reservoir is still matter of debate. Adopting neutron star (NS) fiducial parameters; mass M = 1.4M , radius R = 10 km, and moment of inertia, I = 10 45 g cm 2 , the rotational energy loss,Ė rot , is lower than the observed luminosity (dominated by the X-rays) L X for many of the sources. Aims. We investigate the possibility that some members of this family could be canonical rotation-powered pulsars using realistic NS structure parameters instead of fiducial values. Methods. We compute the NS mass, radius, moment of inertia and angular momentum from numerical integration of the axisymmetric general relativistic equations of equilibrium. We then compute the entire range of allowed values of the rotational energy loss,Ė rot , for the observed values of rotation period P and spin-down rateṖ. We also estimate the surface magnetic field using a general relativistic model of a rotating magnetic dipole. Results. We show that realistic NS parameters lowers the estimated value of the magnetic field and radiation efficiency, L X /Ė rot , with respect to estimates based on fiducial NS parameters. We show that nine SGRs/AXPs can be described as canonical pulsars driven by the NS rotational energy, for L X computed in the soft (2-10 keV) X-ray band. We compute the range of NS masses for which L X /Ė rot < 1. We discuss the observed hard X-ray emission in three sources of the group of nine potentially rotation-powered NSs. This additional hard X-ray component dominates over the soft one leading to L X /Ė rot > 1 in two of them. Conclusions. We show that 9 SGRs/AXPs can be rotation-powered NSs if we analyze their X-ray luminosity in the soft 2-10 keV band. Interestingly, four of them show radio emission and six have been associated with supernova remnants (including Swift J1834.9-0846 the first SGR observed with a surrounding wind nebula). These observations give additional support to our results of a natural explanation of these sources in terms of ordinary pulsars. Including the hard X-ray emission observed in three sources of the group of potential rotation-powered NSs, this number of sources with L X /Ė rot < 1 becomes seven. It remains open to verification 1) the accuracy of the estimated distances and 2) the possible contribution of the associated supernova remnants to the hard X-ray emission.

show abstract

“…These spectra consist of two components (e.g., den Hartog et al 2008a,b;Enoto et al 2010); a quasi-thermal component at low energies, which is generally attributed to the photospheric emission from the neutron star polar cap, and a hard power-law component. In the model of Trümper et al (2010Trümper et al ( , 2013, this power-law component is attributed to the emission from the radiative shock, located near the bottom of the accretion column. This component is emitted as a fan beam, which partly hits the surrounding polar cap, where the radiation is absorbed or scattered, leading to the quasi-thermal component.…”

Section: Introductionmentioning

confidence: 99%

Spectral formation in a radiative shock: application to anomalous X-ray pulsars and soft gamma-ray repeaters

Kylafis

Trümper

Ertan

2014

A&A

Self Cite

View full text Add to dashboard Cite

Context. In the fallback disk model for the persistent emission of anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs), the hard X-ray emission arises from bulk-and thermal Comptonization of bremsstrahlung photons, which are generated in the accretion column. The relatively low X-ray luminosity of these sources implies a moderate transverse optical depth to electron scattering, with photons executing a small number of shock crossings before escaping sideways. Aims. We explore the range of spectral shapes that can be obtained with this model and characterize the most important parameter dependencies. Methods. We use a Monte Carlo code to study the crisscrossing of photons in a radiative shock in an accretion column and compute the resulting spectrum. Results. As expected, high-energy power-law X-ray spectra are produced in radiative shocks with photon-number spectral index Γ > ∼ 0.5. We find that the required transverse optical depth is 1 < ∼ τ ⊥ < ∼ 7. Such spectra are observed in low-luminosity X-ray pulsars. Conclusions. We demonstrate here with a simple model that Compton upscattering in the radiative shock in the accretion column can produce hard X-ray spectra similar to those seen in the persistent and transient emission of AXPs and SGRs. In particular, one can obtain a high-energy power-law spectrum, with photon-number spectral-index Γ ∼ 1 and a cutoff at 100−200 keV, with a transverse Thomson optical depth of ∼5, which is shown to be typical in AXPs/SGRs.

show abstract

An Accretion Model for the Anomalous X-Ray Pulsar 4u 0142+61

Cited by 55 publications

References 63 publications

Pulsars and Magnetars

Pulsars and Magnetars

The rotation-powered nature of some soft gamma-ray repeaters and anomalous X-ray pulsars

Spectral formation in a radiative shock: application to anomalous X-ray pulsars and soft gamma-ray repeaters

Contact Info

Product

Resources

About