Nature 338, 321 - 322 (23 March 1989); doi:10.1038/338321a0

Was the millisecond pulsar in SN1987A spun up or born spinning fast?

S. E. Woosley^* & R. A. Chevalier^†

^*Lick Observatory, Board of Studies in Astronomy and Astrophysics, University of California, Santa Cruz, California 95064, USA
^†Department of Astronomy, University of Virginia, Charlottesville, Virginia 22903, USA

THE discovery¹ of an optical pulsar in SN1987A with a period of 1,968.629 Hz raises many interesting issues, chief among them being the question of how the pulsar came to acquire such a rapid rotation rate. An obvious but possibly incorrect assumption is that it was simply born that way owing to a large specific angular momentum in the iron core that collapsed. Here we argue that this millisecond pulsar, like others observed previously, has been spun up by accretion. In this case the accreted angular momentum comes from the mixed mantle and helium core of the ejecta, of which roughly 0.1 M fell back during the first day after the explosion. This sizeable mass, and hence angular momentum, of the re-imploded material is at least partly a consequence of the blue supergiant nature of the progenitor star.

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