An Etymological Dictionary of Astronomy and Astrophysics

A member of a class of → low-mass X-ray binary systems containing low-magnetic field → neutron stars. They have soft spectra and no pulsations. An example is 4U 1705-44. See also → Z source.

See also: → atoll; the name derives from the fact that on X-ray → color-color diagrams these sources often resemble a band of points at constant hard X-ray color, with “islands” of points appearing on time-scales of weeks and months.