4U 1543-475

4U 1543-475 is a recurrent X-ray transient located in the southern constellation Lupus, the wolf. IL Lupi is its variable star designation. It has an apparent magnitude that fluctuates between 14.6 and 16.7, making it readily visible in large telescopes but not to the naked eye. The object is located relatively far at a distance of approximately 17,000 light years based on Gaia DR3 parallax measurements.

4U 1543-475 was first observed by Uhuru in 1971. In 1976, 4U 1543-475's spectrum was observed. However, its status as a black hole binary had not been confirmed until 1984 by astronomer S. Kiamoto and colleagues. After subsequent observations, it was given the variable star designation IL Lupi in 1995. 4U 1543-475 erupted three times.