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

Ertan, Ünal; Erkut, M. H.

doi:10.1086/524679

Cited by 31 publications

(53 citation statements)

References 33 publications

(56 reference statements)

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“…We note that, in the present work, we have also refined the model parameters obtained by Ertan & Erkut (2008) for XTE J1810−197 considering the newly reported last three data points of this source (Bernardini et al 2009). Illustrative model curves given in Ertan & Erkut (2008) can produce the 2-10 keV absorbed data 1 for a particular α cold .…”

Section: Parametermentioning

confidence: 77%

“…The X-ray outburst light curve of this source showed a different decay morphology than those of persistent sources (Ibrahim et al 2004;Bernardini et al 2009). By means of model fits to the X-ray enhancement data, Ertan & Erkut (2008) concluded that this difference could be due to a viscous disk instability (see, e.g., Lasota 2001 for a review of the disk instability model (DIM)) in the fallback disks at a critical temperature in the ∼1000-2000 K range. The fallback disks around AXPs are expected to have similar chemical compositions.…”

Section: Introductionmentioning

confidence: 89%

“…From model fits to the X-ray enhancement light curve of XTE J1810−197, Ertan & Erkut (2008) found that α cold ∼ 0.03 with T crit ∼ 1500 K produce reasonable model curves. In the present work, we also refine the model parameters of Ertan & Erkut (2008) through a comparative study with the X-ray enhancement light curves of other transient AXPs, including the new data points of XTE J1810−197 (Section 3).…”

Section: Viscosity Parametermentioning

confidence: 98%

“…We solve the disk diffusion equation (see, e.g., Frank et al 2002) in the way described in Ertan & Alpar (2003) and Ertan & Erkut (2008). In this model, it is assumed that a soft gamma-ray burst triggered on the surface of the neutron star pushes the inner disk matter outward.…”

Section: Description Of the Model Parametersmentioning

confidence: 99%

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On the X-Ray Outbursts of Transient Anomalous X-Ray Pulsars and Soft Gamma-Ray Repeaters

Çalışkan¹,

Ertan²

2012

ApJ

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We show that the X-ray outburst light curves of four transient anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs), namely, XTE J1810−197, SGR 0501+4516, SGR 1627−41, and CXOU J164710.2−455216, can be produced by the fallback disk model that was also applied to the outburst light curves of persistent AXPs and SGRs in our earlier work. The model solves the diffusion equation for the relaxation of a disk that has been pushed back by a soft gamma-ray burst. The sets of main disk parameters used for these transient sources are very similar to each other and to those employed in our earlier models of persistent AXPs and SGRs. There is a characteristic difference between the X-ray outburst light curves of transient and persistent sources. This can be explained by the differences in the disk surface density profiles of the transient and persistent sources in quiescence indicated by their quiescent X-ray luminosities. Our results imply that a viscous disk instability operating at a critical temperature in the range of ∼1300-2800 K is a common property of all fallback disks around AXPs and SGRs. The effect of the instability is more pronounced and starts earlier for the sources with lower quiescent luminosities, which leads to the observable differences in the X-ray enhancement light curves of transient and persistent sources. A single active disk model with the same basic disk parameters can account for the enhancement phases of both transient and persistent AXPs and SGRs. We also present a detailed parameter study to show the effects of disk parameters on the evolution of the X-ray luminosity of AXPs and SGRs in the X-ray enhancement phases.

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Section: Parametermentioning

confidence: 77%

Section: Introductionmentioning

confidence: 89%

Section: Viscosity Parametermentioning

confidence: 98%

Section: Description Of the Model Parametersmentioning

confidence: 99%

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On the X-Ray Outbursts of Transient Anomalous X-Ray Pulsars and Soft Gamma-Ray Repeaters

Çalışkan¹,

Ertan²

2012

ApJ

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“…They have been developed in a series of connected, selfconsistent ideas by means of detailed quantitative models (Ekşi & Alpar 2003;Ertan & Alpar 2003;Ertan & Cheng 2004;Ertan et al , 2007Ertan et al , 2009Ertan & Çalışkan 2006;Ertan & Erkut 2008). These models do not explain the super-Eddington bursts.…”

Section: Introductionmentioning

confidence: 99%

The energy spectrum of anomalous X-ray pulsars and soft gamma-ray repeaters

Trümper¹,

Zezas

Ertan

et al. 2010

A&A

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Context. Anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) exhibit characteristic X-ray luminosities (both soft and hard) of around 10 35 erg s −1 and characteristic power-law, hard X-ray spectra extending to about 200 keV. Two AXPs also exhibit pulsed radio emission. Aims. 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. Methods. 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 10 12 −10 13 G, which is what we assume here. Results. 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. Conclusions. 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.

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The strongest cosmic magnets: soft gamma-ray repeaters and anomalous X-ray pulsars

Mereghetti

2008

Astron Astrophys Rev

696

766

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Two classes of X-ray pulsars, the Anomalous X-ray Pulsars and the Soft Gamma-ray Repeaters, have been recognized in the last decade as the most promising candidates for being magnetars: isolated neutron stars powered by magnetic energy. I review the observational properties of these objects, focussing on the most recent results, and their interpretation in the magnetar model. Alternative explanations, in particular those based on accretion from residual disks, are also considered. The possible relations between these sources and other classes of neutron stars and astrophysical objects are also discussed.

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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

Cited by 31 publications

References 33 publications

On the X-Ray Outbursts of Transient Anomalous X-Ray Pulsars and Soft Gamma-Ray Repeaters

On the X-Ray Outbursts of Transient Anomalous X-Ray Pulsars and Soft Gamma-Ray Repeaters

The energy spectrum of anomalous X-ray pulsars and soft gamma-ray repeaters

The strongest cosmic magnets: soft gamma-ray repeaters and anomalous X-ray pulsars

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