Dissipation in relativistic superfluid neutron stars

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

doi:10.1093/mnras/sts129

Cited by 29 publications

(64 citation statements)

References 76 publications

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“…3, where the instability window is splitted by stability peaks). As discussed by Gusakov et al (2014b,a), this picture agrees with detailed calculations of frequencies and damping times for: (i) r-modes and inertial modes of superfluid NSs at zero temperature ; and (ii) f-and p-modes in nonrotating superfluid NSs at finite temperatures (Gusakov & Andersson 2006;Kantor & Gusakov 2011;Chugunov & Gusakov 2011;Gusakov et al 2013;Gualtieri et al 2014). Furthermore, confirm the main features of the resonance uplift scenario by calculating the r-mode spectrum and damping times for a finite-temperature superfluid NS within a simplified model with vanishing entrainment.…”

Section: Resonance Uplift Scenario: Low Temperature Resonances Are Resupporting

confidence: 87%

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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Section: Resonance Uplift Scenario: Low Temperature Resonances Are Resupporting

confidence: 87%

R modes and neutron star recycling scenario

Chugunov¹,

Gusakov²,

Kantor

2017

Monthly Notices of the Royal Astronomical Society

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“…2 The modes of the first type, which we call "normal" (i o -modes) describe comoving oscillations of superfluid and normal matter components and resemble, in many aspects, the corresponding modes of a normal (nonsuperfluid) star [54][55][56][57]. The modes of the second type, which we call "superfluid" (i s -modes) correspond to countermoving oscillations of superfluid and normal matter components and are absent in normal stars.…”

Section: Physics Input and General Equationsmentioning

confidence: 99%

“…[4]). In this paper, we neglect the bulk viscosity, because it is small for the range of stellar temperatures T < 5 × 10 8 K we are interested in (see, e.g., [56,[64][65][66]). One can also freely ignore the effects of mutual friction when considering r o -modes [51,67,68].…”

Section: Physics Input and General Equationsmentioning

confidence: 99%

“…As it has been mentioned above, two types of inertial modes, superfluid and normal ones, exist in rotating NSs. Strictly speaking, these two types are clearly distinct only if one sets to zero the so-called coupling parameter s [54][55][56][57]. In the absence of other mechanisms of mode decoupling (see the end of this section), s = s EOS , where the parameter s EOS depends only on an EOS of superdense matter and is given by [55] …”

Section: Superfluid and Normal Modes A Two Main Assumptionsmentioning

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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“…In [15] we have considered the limit in which superfluid degrees of freedom are decoupled from non-supefluid ones; we found a new class of modes, the superfluid modes, and studied the behaviour of their frequencies and damping times as the temperature of the star changes.…”

Section: Properties Of Differentially Rotating Neutron Starsmentioning

confidence: 99%