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This morning on the radio I heard about the discovery of a pulsar that, due to its proximity to a companion star, was flipping between a state where it emitted radio waves and one where it emitted x-rays. The flipping between states was said to be due to material from the companion star falling onto the pulsar, causing it to rotate more quickly.

What is the significance of this discovery?

This newspaper article from the UK on the discovery contains more information, but doesn't go into detail about why this discovery is important.

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up vote 3 down vote accepted

The significance of this discovery, according to the European Space Agencies web article "Volatile pulsar reveals millisecond missing link" is the first time a pulsar in a crucial transitional phase between has been observed, and that this explains the origin of mysterious millisecond pulsars.

The significance is as stated by the ESA (bolding mine):

This bouncing behaviour is caused by a rhythmical interplay between the pulsar's magnetic field and the pressure of accreted matter.

What this tells us about pulsar dynamics is

When accretion is more intense, the high density of accreted matter inhibits the acceleration of particles that cause radio emission, so the pulsar is not visible in radio waves but only through the X-rays radiated by the accreted matter. When the accretion rate decreases, the magnetosphere expands and pushes matter away from the pulsar: as a consequence, the X-ray emission becomes weaker and weaker, while the radio emission intensifies.

The article also contains contact details of scientists involved

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