BO Carinae
BO Carinae, also known as HD 93420, is an irregular variable star in the constellation Carina.
BO Car has a maximum apparent magnitude of +7.18. Its distance and membership is uncertain, but its possible membership to the star cluster Trumpler 15 allows a distance estimate of approximately . The Gaia Data Release 2 parallax of suggests a closer distance, but the value is considered unreliable due to excess astrometric noise.
BO Car is a red supergiant of spectral type M4Ib with an effective temperature of, a radius of. Its bolometric luminosity is. Mass-loss is on the order of per year.
In 1919, William Matthew Worssell of the Union Observatory announced that the star, then known as CPD-58 2683, is a variable star. It was given its variable star designation, BO Carinae, in 1921. Billed as an irregular variable like TZ Cassiopeiae or V528 Carinae; its apparent brightness fluctuates between magnitude +7.18 and +8.50 without clear periodicity. Some observers have found BO Car not to be variable, but more extensive studies find small amplitude variations with a possible period of 145 days.
Multiple star catalogues list an 11th-magnitude star as a companion to BO Car. The separation was in 2015, and slowly increasing. The companion is a distant blue giant.