Periodic Emission from the Gamma-Ray Binary 1FGL J1018.6–5856

Abstract

Binary Revelation Binary star systems that contain a neutron star or a black hole are expected to emit gamma rays. These gamma-ray binaries are a rare class of objects, which are also expected to emit x-rays. Indeed, several such systems were initially detected through their x-ray emission. The Fermi LAT Collaboration (p. 189 ; see the Perspective by Mirabel ) reports the detection of a gamma-ray binary that was previously unknown as an x-ray source. Follow-up observations reveal that the system is also a source of x-rays and that the companion star is a class O star, a type that is very hot and very luminous.