Page "X-ray pulsar" Paragraph 2

Gas is accreted from the stellar companion and is channeled by the neutron star's magnetic field on to the magnetic poles producing two or more localized X-ray hot spots similar to the two auroral zones on the Earth but far hotter.

At these hotspots the infalling gas can reach half the speed of light before it impacts the neutron star surface.

So much gravitational potential energy is released by the infalling gas, that the hotspots, which are estimated to about one square kilometer in area, can be up to ten thousand times or more luminous than the Sun.