Secular spin-down of the AMP XTE J1751-305

Riggio, A.; Burderi, L.; Salvo, T. Di; Papitto, A.; D’Aí, A.; Iaria, R.; Menna, M. T.

doi:10.1051/0004-6361/201014883

Cited by 38 publications

(37 citation statements)

References 27 publications

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“…Piro & Bildsten (2004) estimated the maximum magnetic field before the shallow surface mode would be dynamically affected to be B dyn ≈ 5 × 10 7 G((ω/2π)/21.4 Hz) which is about 6 × 10 8 G for a rotationally modified shallow surface wave with a frequency of 249.33 Hz. This is close to the estimated value of the magnetic field of J1751 obtained from spin-down measurements due to magneto-dipole radiation which is about 4 × 10 8 G (Riggio et al 2011). However, Heng & Spitkovsky (2009) also explored the effect of a vertical magnetic field on shallow surface waves, and their results suggest that for the spin rate and likely magnetic field strength appropriate to J175, the field does not strongly modify the mode frequencies (see the "magneto-Poincare modes" in their Figure 2).…”

Section: G-modessupporting

confidence: 88%

A Non-Radial Oscillation Mode in an Accreting Millisecond Pulsar?

Strohmayer

Mahmoodifar

2014

ApJ

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We present results of targeted searches for signatures of non-radial oscillation modes (such as r-and g-modes) in neutron stars using RXTE data from several accreting millisecond X-ray pulsars (AMXPs). We search for potentially coherent signals in the neutron star rest frame by first removing the phase delays associated with the star's binary motion and computing fast Fourier transform power spectra of continuous light curves with up to 2 30 time bins. We search a range of frequencies in which both r-and g-modes are theoretically expected to reside. Using data from the discovery outburst of the 435 Hz pulsar XTE J1751−305 we find a single candidate, coherent oscillation with a frequency of 0.5727597 × ν spin = 249.332609 Hz, and a fractional Fourier amplitude of 7.46 × 10 −4 . We estimate the significance of this feature at the 1.6 × 10 −3 level, slightly better than a 3σ detection. Based on the observed frequency we argue that possible mode identifications include rotationally modified g-modes associated with either a helium-rich surface layer or a density discontinuity due to electron captures on hydrogen in the accreted ocean. In the latter case the presence of sufficient hydrogen in this ultracompact system with a likely helium-rich donor would present an interesting puzzle. Alternatively, the frequency could be identified with that of an inertial mode or a core r-mode modified by the presence of a solid crust; however, the r-mode amplitude required to account for the observed modulation amplitude would induce a large spin-down rate inconsistent with the observed pulse timing measurements. For the AMXPs XTE J1814−338 and NGC 6440 X−2 we do not find any candidate oscillation signals, and we place upper limits on the fractional Fourier amplitude of any coherent oscillations in our frequency search range of 7.8 × 10 −4 and 5.6 × 10 −3 , respectively. We briefly discuss the prospects and sensitivity for similar searches with future, larger X-ray collecting area missions.

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Section: G-modessupporting

confidence: 88%

A Non-Radial Oscillation Mode in an Accreting Millisecond Pulsar?

Strohmayer

Mahmoodifar

2014

ApJ

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“…Another potential problem of the trapped disk is the fact that, in at least three AMXPs Patruno 2010;Hartman et al 2011;Papitto et al 2011;Riggio et al 2011) a spin-down has been measured during quiescence and its value is entirely consistent with the expected value from a magnetic dipole spin-down of a neutron star with a field of the order of 10 8 G. There is no clear evidence for enhanced spindown (at least during quiescence) in AMXPs. Moreover, it is difficult to observe spin-down during the declining portion of an outburst due to the short duration of this phase and/or the lower quality of the data.…”

Section: The Accretion Torquementioning

confidence: 99%

The Spin Distribution of Fast-spinning Neutron Stars in Low-mass X-Ray Binaries: Evidence for Two Subpopulations

Patruno

Haskell

Andersson

2017

ApJ

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We study the current sample of rapidly rotating neutron stars in both accreting and non-accreting binaries in order to determine whether the spin distribution of accreting neutron stars in low-mass X-ray binaries can be reconciled with current accretion torque models. We perform a statistical analysis of the spin distributions and show that there is evidence for two sub-populations among low-mass X-ray binaries, one at relatively low spin frequency, with an average of ≈ 300 Hz and a broad spread, and a peaked population at higher frequency with average spin frequency of ≈ 575 Hz. We show that the two sub-populations are separated by a cut-point at a frequency of ≈ 540 Hz. We also show that the spin frequency of radio millisecond pulsars does not follow a log-normal distribution and shows no evidence for the existence of distinct sub-populations. We discuss the uncertainties of different accretion models and speculate that either the accreting neutron star cut-point marks the onset of gravitational waves as an efficient mechanism to remove angular momentum or some of the neutron stars in the fast sub-population do not evolve into radio millisecond pulsars.

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“…The long-term (i.e., months to years) spin variation over periods of X-ray quiescence has been securely measured in only three systems so far (Patruno & Watts 2012). For example, SAXJ1808.4-3658 is the best-timed AMXP and it has a spin-down on the order of 10 −15 Hz s Hartman et al 2011;Papitto et al 2011;Riggio et al 2011).…”

Section: Comparison With the Timing Of Other Amxpsmentioning

confidence: 99%

Timing Observations of PSR J1023+0038 During a Low-Mass X-Ray Binary State

Jaodand

Archibald

Hessels

et al. 2016

ApJ

146

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Transitional millisecond pulsars (tMSPs) switch, on roughly multi-year timescales, between rotation-powered radio millisecond pulsar (RMSP) and accretion-powered low-mass X-ray binary (LMXB) states. The tMSPs have raised several questions related to the nature of accretion flow in their LMXB state and the mechanism that causes the state switch. The discovery of coherent X-ray pulsations from PSRJ1023+0038 (while in the LMXB state) provides us withthe first opportunity to perform timing observationsand to compare the neutron star's spin variation during this state to the measured spin-down in the RMSP state. Whereas the X-ray pulsations in the LMXB state likely indicate that some material is accreting onto the neutron star's magnetic polar caps, radio continuum observations indicate thepresence of an outflow. The fraction of the inflowing material being ejected is not clear, but it may be much larger than that reaching the neutron star's surface. Timing observations can measure the total torque on the neutron star. We have phase-connected nine XMM-Newton observations of PSRJ1023 +0038over the last 2.5 years of the LMXB stateto establish a precise measurement of spin evolution. We find that the average spin-down rate as an LMXB is 26.8±0.4% faster than the rate (−2.39×10 −15 Hz s −1 ) determined during the RMSP state. This shows that negative angular momentum contributions (dipolar magnetic braking, andoutflow) exceed positive ones (accreted material), and suggests that the pulsar wind continues to operate at a largely unmodified level. We discuss implications of this tight observational constraint in the context of possible accretion models.

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Secular spin-down of the AMP XTE J1751-305

Cited by 38 publications

References 27 publications

A Non-Radial Oscillation Mode in an Accreting Millisecond Pulsar?

A Non-Radial Oscillation Mode in an Accreting Millisecond Pulsar?

The Spin Distribution of Fast-spinning Neutron Stars in Low-mass X-Ray Binaries: Evidence for Two Subpopulations

Timing Observations of PSR J1023+0038 During a Low-Mass X-Ray Binary State

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