GR Muscae, also known as 2S 1254-690 is a binary star system in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Musca Musca () is a small constellation in the deep southern sky. It was one of 12 constellations created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman, and it first appeared on a celestial globe in dia ...

composed of a

neutron star A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. white ...

of between 1.2 and 1.8 times the mass of the Sun and a low-mass star likely to be around the mass of the Sun in close orbit. A magnitude 19 blue star was pinpointed as the optical counterpart of the X-ray source in 1978. Its apparent magnitude varies from 18 to 19.1 over a period of 0.16 days. The neutron star has an accretion disk that takes around 6.74 days to complete a revolution, and is inclined at an angle to the incoming stream of material from the donor star.

References

Musca Muscae, GR X-ray binaries Neutron stars {{Var-star-stub