Instability Windows and Evolution of Rapidly Rotating Neutron Stars

Gusakov, M. E.; Chugunov, A. I.; Kantor, E. M.

doi:10.1103/physrevlett.112.151101

Cited by 59 publications

(83 citation statements)

References 72 publications

(176 reference statements)

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“…A possible solution to this problem was suggested in our recent paper [33] and is discussed in more detail here. Our key idea consists in that to study evolution of NSs in LMXBs one has to correctly take into account the resonance interaction between the normal oscillation m = 2 r-mode and superfluid inertial modes, which occurs at some fixed values of T ∞ (see Sec.…”

Section: Introductionmentioning

confidence: 94%

“…Point B lies on the instability curve at T ∞ = T ∞ eq , and specifies the frequency of point C. Points D and E do not depend on the position of m = 2 r o -mode instability curve. 16 In principle, the magnetic field can limit accretion spin-up before reaching point D [33,87]. 17 It is convenient to use −τ GR II instead of τ Diss II in Eq.…”

mentioning

confidence: 99%

“…[33,121] it is argued that these nonaccreting NSs, heated by the CFS instability, form a specific new class of NSs. These references propose to call them "HOFNARs" (from HOt and Fast Non-Accreting Rotators) or "hot widows" (in analogy with the "black widow" pulsars), and suggest that a number of sources that are tentatively identified as quiescent LMXB candidates may in fact be such objects.…”

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confidence: 99%

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Explaining observations of rapidly rotating neutron stars in low-mass x-ray binaries

2014

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In a previous paper [M. E. Gusakov, A. I. Chugunov, and E. M. Kantor, Phys. Rev. Lett. 112, 151101 (2014)], we introduced a new scenario that explains the existence of rapidly rotating warm neutron stars (NSs) observed in low-mass X-ray binaries (LMXBs). Here it is described in more detail. The scenario takes into account the interaction between superfluid inertial modes and the normal (quadrupole) m = 2 r-mode, which can be driven unstable by Chandrasekhar-Friedman-Schutz (CFS) mechanism. This interaction can only occur at some fixed "resonance" stellar temperatures; it leads to formation of the "stability peaks" which stabilize a star in the vicinity of these temperatures. We demonstrate that a NS in LMXB spends a substantial fraction of time on the stability peak, that is, in the region of stellar temperatures and spin frequencies, that has been previously thought to be CFS unstable with respect to excitation of r-modes. We also find that the spin frequencies of NSs are limited by the CFS instability of normal (octupole) m = 3 r-mode rather than by m = 2 r-mode. This result agrees with the predicted value of the cutoff spin frequency ∼ 730 Hz in the spin distribution of accreting millisecond X-ray pulsars. In addition, we analyze evolution of a NS after the end of the accretion phase and demonstrate that millisecond pulsars can be born in LMXBs within our scenario. Besides millisecond pulsars, our scenario also predicts a new class of LMXB descendants-hot and rapidly rotating nonaccreting NSs ("hot widows"/HOFNARs). Further comparison of the proposed theory with observations of rotating NSs can impose new important constraints on the properties of superdense matter.

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Section: Introductionmentioning

confidence: 94%

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confidence: 99%

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confidence: 99%

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Explaining observations of rapidly rotating neutron stars in low-mass x-ray binaries

2014

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“…General equations that describe evolution of a NS affected by r-mode instability were formulated by Lindblom et al (1998) (see also Levin 1999;Ho & Lai 2000;Alford & Schwenzer 2014a;Gusakov et al 2014b) and the typical evolution track is shown by a thick black line in Fig. 1.…”

Section: Minimal R-mode Instability Modelmentioning

confidence: 99%

R modes and neutron star recycling scenario

Chugunov¹,

Gusakov²,

Kantor

2017

Monthly Notices of the Royal Astronomical Society

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To put new constraints on the r-mode instability window, we analyse the formation of millisecond pulsars (MSPs) within the recycling scenario, making use of three sets of observations: (a) X-ray observations of neutron stars (NSs) in low-mass X-ray binaries; (b) timing of millisecond pulsars; and (c) X-ray and UV observations of MSPs. As shown in previous works, r-mode dissipation by shear viscosity is not sufficient to explain observational set (a), and enhanced r-mode dissipation at the red-shifted internal temperatures T ∞ ∼ 10 8 K is required to stabilize the observed NSs. Here, we argue that models with enhanced bulk viscosity can hardly lead to a self-consistent explanation of observational set (a) due to strong neutrino emission, which is typical for these models (unrealistically powerful energy source is required to keep NSs at the observed temperatures). We also demonstrate that the observational set (b) , combined with the theory of internal heating and NS cooling, provides evidence of enhanced r-mode dissipation at low temperatures, T ∞ ∼ 2×10 7 K. Observational set (c) allows us to set an upper limit on the internal temperatures of MSPs, T ∞ < 2 × 10 7 K (assuming a canonical NS with the accreted crust). Recycling scenario can produce MSPs at these temperatures only if r-mode instability is suppressed in the whole MSP spin frequency range (ν 750 Hz) at temperatures 2 × 10 7 T ∞ 3 × 10 7 K, providing thus a new constraint on the r-mode instability window. These observational constraints are analysed in more details in application to the resonance uplift scenario of Gusakov et al. (2014b,a).

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“…11 by dots with error bars associated with uncertainty in thermal insulating envelope composition; data are taken from Gusakov, Chugunov & Kantor 2014b;Chugunov, Gusakov & Kantor 2017) reveal the inadequacy of the standard model: additional dissipation of r-modes is required to stabilize many observed NSs [i.e., all NSs in the white region of 11(a)]. Chugunov et al (2017) analyze the formation of MSPs via the recycling scenario (Bisnovatyi-Kogan & Komberg 1976;Alpar et al 1982;Bhattacharya & van den Heuvel 1991;Papitto et al 2013) and suggest 'minimal' constraints to the instability windows, which allow them to explain the observations of transiently accreting neutron stars, and the formation of high-frequency MSPs, simultaneously.…”

Section: Upper Limit For Surface Temperature Of Msp 47 Tuc Aa and Conmentioning

confidence: 99%

Chandra studies of the globular cluster 47 Tucanae: a deeper X-ray source catalogue, five new X-ray counterparts to millisecond radio pulsars and new constraints to r-mode instability window

Bhattacharya

Heinke

Chugunov

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We combined Chandra ACIS observations of the globular cluster 47 Tucanae (hereafter, 47 Tuc) from 2000, 2002, and 2014-15 to create a deeper X-ray source list, and study some of the faint radio millisecond pulsars (MSPs) present in this cluster. We have detected 370 X-ray sources within the half-mass radius (2 .79) of the cluster, 81 of which are newly identified, by including new data and using improved source detection techniques. The majority of the newly identified sources are in the crowded core region, indicating cluster membership. We associate five of the new X-ray sources with chromospherically active BY Dra or W UMa variables identified by Albrow et al. (2001). We present alternative positions derived from two methods, centroiding and image reconstruction, for faint, crowded sources. We are able to extract X-ray spectra of the recently discovered MSPs 47 Tuc aa, 47 Tuc ab, the newly timed MSP 47 Tuc Z, and the newly resolved MSPs 47 Tuc S and 47 Tuc F. Generally, they are well fit by black body or neutron star atmosphere models, with temperatures, luminosities and emitting radii similar to those of other known MSPs in 47 Tuc, though 47 Tuc aa and 47 Tuc ab reach lower X-ray luminosities. We limit X-ray emission from the full surface of the rapidly spinning (542 Hz) MSP 47 Tuc aa, and use this limit to put an upper bound for amplitude of r-mode oscillations in this pulsar as α < 2.5 × 10 −9 and constrain the shape of the r-mode instability window.

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Instability Windows and Evolution of Rapidly Rotating Neutron Stars

Cited by 59 publications

References 72 publications

Explaining observations of rapidly rotating neutron stars in low-mass x-ray binaries

Explaining observations of rapidly rotating neutron stars in low-mass x-ray binaries

R modes and neutron star recycling scenario

Chandra studies of the globular cluster 47 Tucanae: a deeper X-ray source catalogue, five new X-ray counterparts to millisecond radio pulsars and new constraints to r-mode instability window

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