Pulsar cannibalizes companion.
The companion star of one of the fastest-spinning puslars yet foud is evaporating, and Columbia University scientist Wlodzimierz Kluzniak and his colleagues have proposed a model that explains the behavior of this pair and the dearth of other such pairs in the universe.
Observations suggest the pulsar is eating away at its companion, tearing it apart with gamma-ray bombardment and then using its gases to feed the pulsar's appetite for more mass and faster spin. In the early stage of the pair's evolution, according to Kluzniak and his associates, the pulsar -- a rapidly spinning, very dense neutron star -- is surrounded by an accretion disk of matter that falls onto the surface of the pulsar and makes it spin faster. The accretion disk also radiates gamma rays that "evaporate" matter from the companion's surface, Kluzniak and his co-workers propose in the July 21 NATURE. In the second stage of the pair's evolution, after the accretion disk is consumed by the neutron star, the pulsar itself radiates enough energy to tear matter from the companion star.
This matter is pulled onto the ever-more-rapidly spinning pulsar. After about 100 million years the companion should be completely gone, Kluzniak says.
Such parasitism was proposed in December, but this is the first good example of it, Kluzniak says. Kluzniak and two Dutch astronomers have suggested this mechanism may account for the scacity of certain binary-system pulsars with low-mass companion stars. When a companion star is small enough and close enough to a pulsar, Kluzniak and his colleagues suggest, the pulsar consumes it in a relatively short period.
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|Date:||Jul 30, 1988|
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