A low-mass X-ray pulsar about 15 000 l.y. away in the constellation Hercules. It is an eclipsing binary consisting of a visible star of about 14th magnitude accompanied by a neutron star. Material from the visible star is accreted by the neutron star, releasing its gravitational energy as X-rays. The optical counterpart, HZ Herculis, varies in spectral type from A to B during each orbit due to X-ray heating. The rapid spin of the neutron star produces X-ray pulses every 1.24 s, and the stars eclipse each other every 1.7 days.