GR Muscae
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Musca |
| Right ascension | 12h 57m 37.153s |
| Declination | −69° 17′ 18.98″ |
| Apparent magnitude (V) | 19.1 |
| Database references | |
| SIMBAD | data |
GR Muscae, also known as 2S 1254-690 is a binary star system in the constellation Musca composed of a neutron star 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.
While the optical counterpart to the X-ray source was identified in 1978, optical variability was not detected until 1980, when a bright flare was seen that increased the white-light flux by a factor of two in a time interval of about 1.7 seconds. GR Muscae received its variable star designation in 1985.
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.