Imprint of magnetic obliquity in apparent spin-down of radio pulsars

Numerical simulations predict that the spin-down rate of a single rotation-powered neutron star depends on the angle abetween its spin and magnetic axes as P P proportional to mu(2) (k(0) + k(1) sin(2) alpha), where P is the star spin period, mu is its magnetic moment, while k(0) similar to k(1) similar to 1. Here, we describe a simple observational test for this prediction based on the comparison of spin-down rates of 50 nearly orthogonal (with alpha close to 90 deg) and 27 nearly aligned (with aclose to 0 deg) pulsars. We found, that the apparent pulsar spin-down is consistent with the theory if assumed, that magnetic moments of orthogonal rotators are systematically larger than those of aligned ones for similar to 0.15...0.2 dex. Also, as a by-product of the analysis, we provide yet another constraint on the average braking index of radio pulsars as 1 <= n <= 4 with formal significance not worse than 99 per cent.