for KV Ursae Majoris, adapted from Cherepashchuk
et al. (2019) The
compact object in XTE J1118+480 has a mass greater than , so it is too massive to be a
neutron star. The characteristics of radio emissions from XTE J1118+480 (Fender
et al. 2001) suggest that it is a
microquasar. Strangely, the companion star has a metal-rich composition of various metals such as magnesium, aluminium, calcium, iron, and nickel. Because of this observation, the black hole most likely was not formed from direct collapse of a massive star, but rather from the
supernova of a
metal-rich star. The two objects in the
binary system were probably not born together as a supernova would likely eject the companion from the system. The most likely theory as to how the black hole became part of the binary system is that XTE J1118+480 was formed in the central
galactic halo. The black hole primary was the result of a "kick" from the supernova explosion of a massive star in the early galaxy and travelled through the galaxy and into the central galactic halo, becoming a binary system with its present-day companion. If this theory is true, it may help to explain the
supernova mechanism. The black hole in XTE J1118+480 is one of the few known examples of a
black hole kick. == See also==