CP Puppis


CP Puppis was a bright nova occurring in the constellation Puppis in 1942. From a 17th magnitude star, it reached an apparent visual magnitude of –0.2 then began a rapid decline. It had dropped by three magnitudes in an interval of 6.5 days, one of the sharpest declines ever noted for a nova. About 14 years later, the shell ejected by the nova event was detected, which allowed the distance to be computed. In 2000, this distance was revised to after correcting for probable errors. The Gaia spacecraft later measured the parallax of the star leading to an accurate distance of parsecs.
The nova outburst can be explained by a white dwarf that is accreting matter from a companion; most likely a low-mass main sequence star. This close binary system has an orbital period of 1.47 hours, which is one of the shortest periods of the known classical nova. Unusually, the white dwarf may have a magnetic field. Other properties of the system remain uncertain, although observations of X-ray emission from the system suggest that the white dwarf has a mass of more than 1.1 times the mass of the Sun.