Millisecond pulsars with r-modes as steady gravitational radiators

Abstract

Millisecond pulsars (MSPs) are generally agreed to originate in low-mass X-ray binaries (LMXBs), in which mass transfer onto the neutron stars spins them up to their observed, fast rotation. The lack of MSPs and LMXBs rotating near break-up and the similar rotation periods of several LMXBs have been attributed to the accretion torque being balanced, at fast rotation, by gravitational radiation, perhaps caused by an oscillation mode made unstable through the so-called Chandrasekhar-Friedman-Schutz mechanism. Recently, Wagoner has argued that internal dissipation through weak interaction processes involving ${\Lambda }^0$ and ${\Sigma }^{-}$ hyperons may cause LMXBs to evolve into a quasi-steady state, in which the neutron star has a nearly constant rotation rate, temperature, and mode amplitude. We take this hypothesis one step further, showing that MSPs descending from these LMXBs spend a long time in a similar state, in which a low-amplitude r-mode turns them into extremely steady sources of both gravitational waves and thermal X-rays, while they spin down due to a combination of gravitational radiation and the standard magnetic torque. Observed MSP braking torques already place meaningful constraints on the allowed gravitational wave amplitudes and dissipation mechanisms.

4 pages, 2 figures, accepted for publication in Phys Rev Lett, added/modified content: superfluidity has been considered and clarification of some aspects as requested by referees

References in corpus (19)

• A new class of unstable modes of rotating relativistic stars
• Gravitational Radiation and Rotation of Accreting Neutron Stars
• Gravitational waves from hot young rapidly rotating neutron stars
• Gravitational Radiation Instability in Hot Young Neutron Stars
• Axial instability of rotating relativistic stars
• Searching for periodic sources with LIGO. II: Hierarchical searches
• Saturation of the R-mode Instability
• The Ocean and Crust of a Rapidly Accreting Neutron Star: Implications for Magnetic Field Evolution and Thermonuclear Flashes
• Effect of hyperon bulk viscosity on neutron-star r-modes
• Runaway Heating By R-modes of Neutron Stars in Low Mass X-ray Binaries
• Strange stars as persistent sources of gravitational waves
• Crust-core coupling and r-mode damping in neutron stars: a toy model
• R-Modes in Superfluid Neutron Stars
• Bulk viscosity in superfluid neutron star cores. III. Effects of ${\Sigma }^{-}$ hyperons
• Binary and Millisecond Pulsars at the New Millennium
• Conditions for Steady Gravitational Radiation from Accreting Neutron Stars
• Constraining dense-matter superfluidity through thermal emission from millisecond pulsars
• Magnetic effects on the viscous boundary layer damping of the r-modes in neutron stars
• R-modes in Neutron Stars with Crusts: Turbulent Saturation, Spin-down, and Crust Melting

Cited by in corpus (32)

• Physics, Astrophysics and Cosmology with Gravitational Waves
• Spinning down newborn neutron stars: nonlinear development of the r-mode instability
• How to adapt broad-band gravitational-wave searches for r-modes
• R-modes of accreting hyperon stars as persistent sources of gravitational waves
• First all-sky search for continuous gravitational waves from unknown sources in binary systems
• Ekman layer damping of r-modes revisited
• What the Timing of Millisecond Pulsars Can Teach us about Their Interior
• Viscous damping of r-modes: Small amplitude instability
• Instability windows and evolution of rapidly rotating neutron stars
• Viscous damping of r-modes: Large amplitude saturation
• Crust-core coupling in rotating neutron stars
• 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
• Gravitational wave emission from oscillating millisecond pulsars
• Bulk viscosity in neutron stars with hyperon cores
• R-modes and neutron star recycling scenario
• Constraining neutron superfluidity with $r$-mode physics
• New possible class of neutron stars: hot and fast non-accreting rotators
• A compact star rotating at 1122 Hz and the r-mode instability
• Gravitational-wave astronomy: the high-frequency window
• All-sky radiometer for narrowband gravitational waves using folded data
• Gravitational Wave Astronomy
• Strengthening the bounds on the r-mode amplitude with X-ray observations of millisecond pulsars
• Signatures of quark deconfinement through the r-modes of twin stars
• All-sky, narrowband, gravitational-wave radiometry with folded data
• Coherently combining short data segments for all-sky semi-coherent continuous gravitational wave searches
• Gravitational wave bursts induced by r-mode spin-down of hybrid stars
• Magnetic field generated by r-modes in accreting quark stars
• Colloquium: Multimessenger astronomy with continuous gravitational waves and future detectors
• Long term evolution of CFS-unstable neutron stars and role of differential rotation on short time-scales
• Instability windows of relativistic r-modes in stably stratified neutron stars with hyperonic cores
• Rossby modes in neutron stars as sources of gravitational waves
• Constraints on r-modes and mountains on millisecond neutron stars in binary systems