Article Abstract:
The explosion of supernova SN1987A on Feb 23, 1987 was believed to presage the formation of a pulsar, but no evidence of a pulsing neutron star has been observed. Some, but not all, of the present luminosity of SN1987A results from decay of radioactive cobalt. The excess apparently does not result from a neutron star but from physical processes following the explosion. An observed 10-second neutrino pulse at the time of explosion indicates that a neutron star was formed. It is possible that there is no evidence of it after then because a black hole formed when the star collapsed.
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Article Abstract:
The hypothesis that gamma-ray bursts are produced by neutrons stars inside the Milky Way Galaxy got a boost from Hui Li and Charles D. Dermer's analysis of data showing that such bursts are spread isotropically through space. This analysis linked the bursts to newly spotted groups of high-velocity radio pulsars, which are young neutron stars with powerful magnetic fields. However, an alternative hypothesis maintains that the bursts derive from outside the Galaxy. Further research is required to settle which of these hypotheses is correct.
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Article Abstract:
Occasional sudden jumps in the frequency at which a pulsar emits its signal have prompted theories of neutron stars' internal structure that would account for the irregularities. A.G. Lyne and his colleagues hypothesize that a neutron star may have four distinct zones that rotate at different rates. The glitches would then result from friction between the zones and conservation of angular momentum.
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