Accretion torque on magnetized neutron stars

Dai, Hai-Lang; Li, Xiang-Dong

doi:10.1051/0004-6361:20053907

Cited by 34 publications

(36 citation statements)

References 34 publications

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“…where r co = (GM/(2πν) 2 ) 1/3 is the corotation radius at which the centrifugal forces balance the gravitational forces, w c is the critical fastness parameter at which the accretion torque is expected to vanish. The critical fastness parameter w c has been estimated to be ∼0.35 and depends on the electrodynamics of the disc (Ghosh & Lamb 1979;Wang 1987;Ghosh 1993;Li & Wickramasinghe 1998;Torkelsson 1998;Dai & Li 2006). The accreted material will produce X-ray emission at the neutron star surface with a luminosity expressed as…”

Section: Discussionmentioning

confidence: 99%

Timing studies on RXTE observations of SAX J2103.5+4545

Baykal

İnam

Stark

et al. 2007

Monthly Notices of the Royal Astronomical Society

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SAX J2103.5+4545 has been continuously monitored for ∼900 d by the Rossi X‐ray Timing Explorer (RXTE) since its outburst in 2002 July. Using these observations and previous archival RXTE observations of SAX J2103.5+4545, we refined the binary orbital parameters and find the new orbital period as P= (12.665 36 ± 0.000 88) d and the eccentricity as 0.4055 ± 0.0032. With these new orbital parameters, we constructed the pulse frequency and pulse frequency derivative histories of the pulsar and confirmed the correlation between X‐ray flux and pulse frequency derivative presented by Baykal, Stark & Swank. We constructed the power spectra for the fluctuations of pulse frequency derivatives and found that the power‐law index of the noise spectra is 2.13 ± 0.6. The power‐law index is consistent with random walk in pulse frequency derivative and is the steepest among the HMXRBs. X‐ray spectra analysis confirmed the inverse correlation trend between power‐law index and X‐ray flux found by Baykal et al.

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Section: Discussionmentioning

confidence: 99%

Timing studies on RXTE observations of SAX J2103.5+4545

Baykal

İnam

Stark

et al. 2007

Monthly Notices of the Royal Astronomical Society

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“…The accretion torque, N , exerted on the compact star is made up of two contributions: one is the positive material torque, which is carried by the material falling onto the star's surface; the other is the magnetic torque, which can be positive or negative, depending on the fastness parameter ω s =Ω ★ /Ω K = ( r m / r c ) 3/2 . It is suggested that the torques may cancel one another if the fastness parameter is ω s = ( r m / r c ) 3/2 ≈ 0.884 (Dai & Li 2006). This implies a magnetospheric radius of r m = 0.92 r c ≈ r c .…”

Section: Submillisecond Pulsars Formed Through Accretion In Binary mentioning

confidence: 99%

The formation of submillisecond pulsars and the possibility of detection

Qiao

et al. 2009

Monthly Notices of the Royal Astronomical Society

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Pulsars have been recognized to be normal neutron stars, but sometimes have been argued to be quark stars. Submillisecond pulsars, if detected, would play an essential and important role in distinguishing quark stars from neutron stars. We focus on the formation of such submillisecond pulsars in this paper. A new approach to the formation of a submillisecond pulsar (quark star) by means of the accretion‐induced collapse (AIC) of a white dwarf is investigated. Under this AIC process, we found that: (i) almost all newborn quark stars could have an initial spin period of ∼0.1 ms; (ii) nascent quark stars (even with a low mass) have a sufficiently high spin‐down luminosity and satisfy the conditions for pair production and sparking process and appear as submillisecond radio pulsars; (iii) in most cases, the times of newborn quark stars in the phase with spin period <1 (or <0.5) ms are long enough for the stars to be detected. As a comparison, an accretion spin‐up process (for both neutron and quark stars) is also investigated. It is found that quark stars formed through the AIC process can have shorter periods (≤0.5 ms), whereas the periods of neutron stars formed in accretion spin‐up processes must be longer than 0.5 ms. Thus, if a pulsar with a period shorter than 0.5 ms is identified in the future, it could be a quark star.

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“…The magnetospheric torque in equation (2) represents the flux of angular momentum transferred to the magnetic field of the neutron star as the disk matter couples with the field lines at r ¼ r A and accretes onto the star over the range r co r r A (see, e.g., Dai & Li 2006). The azimuthal component of the magnetic field can be written as B þ ¼ B z , where is the azimuthal pitch of order unity and > 0 for r k r co (see Wang 1995).…”

Section: Spin Evolution Of the Transient Axp Xte J1810à197mentioning

confidence: 99%

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

Erkut

2008

ApJ

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We show that (1) the long-term X-ray outburst light curve of the transient AXP XTE J1810À197 can be accounted for by a fallback disk that is evolving toward quiescence through a disk instability after having been heated by a soft gamma-ray burst, (2) the spin-frequency evolution of this source in the same period can also be explained by the disk torque acting on the magnetosphere of the neutron star, and (3) most significantly, recently observed pulsed-radio emission from this source coincides with the epoch of minimum X-ray luminosity. This is natural in terms of a fallbackdisk model, as the accretion power becomes so low that it is not sufficient to suppress the beamed radio emission from XTE J1810À197.

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Accretion torque on magnetized neutron stars

Cited by 34 publications

References 34 publications

Timing studies on RXTE observations of SAX J2103.5+4545

Timing studies on RXTE observations of SAX J2103.5+4545

The formation of submillisecond pulsars and the possibility of detection

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

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