Pulsational magnetic radiation from the neutron star in supernova 1987A

Abstract

THE 0.5-millisecond period of pulsar PSR0535-69 in supernova 1987A (ref. 1) may be hard to explain by a conventional rotating neutron-star model, but might more naturally be understood if the neutron star is undergoing radial pulsation². If this is the case, the pulsations will give rise to a time-varying dipole moment, and thus to electromagnetic radiation. I show here that any pulsar heating of the supernova remnant greater than ∼1.5 x 10³⁷ erg s⁻¹ must be due to this pulsational magnetic radiation (PMR). Recent observations^3,4 suggest a pulsar power ∼7xl0³⁷ ergs^-1. This implies that PMR is indeed heating the supernova nebula, and that the amplitude of the neutron-star surface oscillation after ∼2 yr is ∼10 B⁻¹₁₂ m, where B₁₂ is the polar magnetic field in units of 10¹² Gauss. The vibrating pulsar model makes several testable predictions: in particular, any PMR component in the light curve will have a characteristic decay time of ∼0.5 yr (with large uncertainty) which is the result of rotation-induced damping by gravitational radiation. This would be very different from the usual pulsar heating rate, which is approximately flat on timescales of the order of years.