Kostas Glampedakis, Ian D. Jones, Lars Samuelsson
Rotating neutron stars can become potent sources of gravitational radiation if their shape can be made non-spherical and non-axisymmetric. Such deformations (colloquially known as "mountains") can be induced by forces internal to the star, for example, by the strong stellar magnetic field.
The expected magnetic deformation is typically too small to make any known neutron star detectable by present and next generation gravitational wave detectors, however, as we have recently shown the presence of stable quark matter in neutron star interiors could be a game changer. Internal magnetic mountains induced in a "color-superconducting" quark core could make young pulsars, like the Crab and Vela, "visible" sources of gravitational waves, hence providing us with evidence of the existence of exotic matter inside these extreme objects.
Reference / Figure
Phys. Rev. Letters 109, 081103 (2012) arXiv e-print (arXiv:1204.3781)