LMC X-1
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Dorado |
| Right ascension | 05h 39m 38.8284s |
| Declination | −69° 44′ 35.5315″ |
| Apparent magnitude (V) | 14.612 ± 0.171 |
| Characteristics | |
| Evolutionary stage | X-ray binary |
| Spectral type | O8 IIIf or O8 f?p |
| Astrometry | |
| Radial velocity (Rv) | 309.12 ± 0.333 km/s |
| Proper motion (μ) | RA: 1.889 ± 0.020 mas/yr Dec.: 0.622 ± 0.023 mas/yr |
| Distance | 180,000 ly (55,000 pc) |
| Orbit | |
| Primary | giant star |
| Companion | black hole |
| Period (P) | 3.90917 ± 0.00005 days |
| Semi-major axis (a) | 36.49 ± 1.51 R☉ |
| Eccentricity (e) | <0.0256 ± 0.0066 |
| Inclination (i) | 36.38 ± 2.02° |
| Semi-amplitude (K2) (secondary) | 71.61 ± 1.10 km/s |
| Details | |
| star | |
| Mass | 31.79 ± 3.48 M☉ |
| Radius | 17.0 ± 0.8 R☉ |
| Surface gravity (log g) | 3.485 ± 0.018 cgs |
| Temperature | 33,000 to 35,000 K |
| Rotational velocity (v sin i) | 129.9 ± 2.2 km/s |
| Age | 5 Myr |
| black hole | |
| Mass | 10.91 ± 1.41 M☉ |
| Other designations | |
| 2MASS J05393883-6944356, 2E 1522, 1RXS J053938.8-694515 | |
| Database references | |
| SIMBAD | data |
LMC X-1 is the first X-ray source detected in the Large Magellanic Cloud. It was discovered in 1969, using data from an instrument carried by a Sandia Terrier-Sandhawk sounding rocket, launched from the Johnston Atoll on October 29, 1968. LMC X-1 is a persistently luminous X-ray binary.
In the 80s Hutchings et al. performed spectroscopic follow-up observations of the optical counterpart and found an orbital period of about 4 days and a secondary mass of about 6 M☉, making the secondary a stellar mass black hole. The orbital period later turned out to be shorter at around 3.9 days. The optical counterpart is also called "star 32". The black hole has a mass of around 11 M☉ and the star has a mass of around 32 M☉ and a radius of 17 R☉. With this radius the star nearly fills its Roche lobe and it is predicted that it will encounter its Roche lobe in a few hundred thousand years. Once it reaches its Roche lobe, it will begin rapid and possibly unstable mass transfer to its companion.
The X-ray source is surrounded by a nebula, which is the only nebula energized by an X-ray binary. It is suspected that the nebula is a bow shock nebula. The nebula is also detected in radio wavelengths with ATCA imaging. A possible origin of LMC X-1 is the star cluster [NKN2005] N159-O1. Other possible origins are NGC 2077, NGC 2080, NGC 2085 and NGC 2086. In the scenario of N159-O1 being the origin, the progenitor to the black hole would have a mass of about 60 M☉, meaning it was the most massive member of this star cluster.