LMC X-1

LMC X-1 is the first X-ray source detected in the Large Magellanic Cloud. It was discovered in 1969, using data from a 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, 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 and the star has a mass of around 32  and a radius of 17. 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, meaning it was the most massive member of this star cluster.