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Title: Why do fast-spinning accreting neutron stars evade the r-mode instability?
Plain: Theory says certain sloshing oscillations called r-modes should grow on their own in fast-spinning neutron stars, radiate gravitational waves and slow the stars down. Yet many observed stars spin fast in the region where this should happen.
Precise: With standard shear and bulk viscosity, low-mass X-ray binaries spinning at $300\ \text{to}\ 700\ \mathrm{Hz}$ with inferred core temperatures of about $1e8\ \mathrm{K}$ lie inside the r-mode instability window. Determine the extra damping (viscous crust-core boundary layer, hyperon or quark bulk viscosity, superfluid mutual friction, resonances) or the low saturation amplitude that reconciles theory with the observed spin and temperature distribution.
Settled by: A calculation of r-mode damping and nonlinear saturation in realistic stellar models that places the observed systems outside the window or predicts their spin-temperature distribution.
Kind: phenomenon
Answer type: mechanism
References: (empty)
Literature status: open
Status note: (empty)
Posed since: (empty)