Gravitational wave emission and Gravitational wave spindown of young pulsars

Abstract

The rotation frequencies of young pulsars are systematically below their theoretical Kepler limit. R-modes have been suggested as a possible explanation for this observation. With the help of semi- analytic expressions that make it possible to assess the uncertainties of the r-mode scenario due to the impact of uncertainties in underlying microphysics, we perform a quantitative analysis of the the spin-down and the emitted gravitational waves of young pulsars. We find that the frequency to which r-modes spin down a young neutron star as well as the characteristic gravitational wave strain amplitude are extremely insensitive both to the microscopic details and the saturation amplitude. Comparing our result to astrophysical data, we show that for a range of saturation amplitudes r- modes provide a viable spindown scenario and that all observed young pulsars are very likely already outside the r-mode instability region. Taking into account the finite observation time, we find that the signal to noise ratio for gravitational waves is smaller than previous estimates, but large enough to detect such sources with next generation detectors.