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Radio emission from a pulsar’s magnetic pole revealed by general relativity

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Science  06 Sep 2019:
Vol. 365, Issue 6457, pp. 1013-1017
DOI: 10.1126/science.aav7272

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General relativity reveals pulsar beams

Pulsars are rotating neutron stars that emit beams of radio waves along their magnetic poles, seen as regular pulses if the beam points toward Earth. Desvignes et al. monitored a pulsar for more than a decade, observing how its radio pulses vary. General relativity causes precession of the rotation axis, because of the influence of a binary companion. In 2005, two pulses per rotation were visible, one from each magnetic pole, but by 2018 one had precessed out of our line of sight and disappeared. Mapping the radio emission across the magnetic pole determines the beaming angle, the angular region in which a radio observer can detect a pulsar.

Science, this issue p. 1013

Abstract

Binary pulsars are affected by general relativity (GR), causing the spin axis of each pulsar to precess. We present polarimetric radio observations of the pulsar PSR J1906+0746 that demonstrate the validity of the geometrical model of pulsar polarization. We reconstruct the (sky-projected) polarization emission map over the pulsar’s magnetic pole and predict the disappearance of the detectable emission by 2028. Two tests of GR are performed using this system, including the spin precession for strongly self-gravitating bodies. We constrain the relativistic treatment of the pulsar polarization model and measure the pulsar beaming fraction, with implications for the population of neutron stars and the expected rate of neutron star mergers.

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