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Is the 5-kpc galactic arm a colony of X-ray pulsars?


MORE than two dozen binary X–ray pulsars have been discovered in our Galaxy 1 . Because of instrumental constraints, however, most of these have been discovered within only a few kiloparsecs (kpc) of the Sun. Here we report the discovery by the Ginga satellite of four X-ray pulsars and three hard X-ray sources in the galactic plane at galactic latitude l ≈30° and a distance of about 10 kpc (the '5–kpc arm ' 2 ). This indicates that the 5–kpc arm has been the site of vigorous formation of X-ray pulsars, and that in general their distribution might be expected to be non-uniform.

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Koyama, K., Kawada, M., Kunieda, H. et al. Is the 5-kpc galactic arm a colony of X-ray pulsars?. Nature 343, 148–149 (1990).

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