Does supernova 1987A contain a rapidly vibrating neutron star?

Abstract

IF the recently reported^1,2 0.5-ms-period pulsed optical signal from the direction of supernova 1987A originated in a young neutron star, its interpretation as a rotational period has difficulties. The surface magnetic field would have to be much lower than expected, and the high rotation rate may rule out preferred nuclear equations of state^3,4. Here we point out that a remnant radial vibration of a neutron star, excited in the supernova event, may survive for several years with about the observed (gravitationally red-shifted) period. Heavy ions at the low-density stellar surface, periodically shocked by the vibration, may efficiently produce narrow pulses of optical cyclotron radiation in a surface field of ∼10¹² gauss. These pulses may be modulated only slightly by a much slower stellar rotation because of the nearly isotropic emission mechanism and smearing from the strong gravitational bending of light rays^5,6. We do not attempt to explain the reported¹ 8-hour modulation, which may be a result of timing noise (ref. 7 and J. Katz, preprint).