HD 133880
HD 133880, also known as HR 5624 and HR Lupi, is a Bp star about 340 light years from the Earth, in the constellation Lupus. It is a 5th magnitude star, and will be faintly visible to the naked eye of an observer far from city lights. It is an SX Arietis variable star, varying from magnitude 5.76 to 5.81 over a period of 21.0594 hours. HD 133880 is a member of the Upper Centaurus–Lupus association. It is a young star, estimated to have completed only percent of its projected main sequence lifetime. It is one of the few stars known to produce coherent pulsed radio radiation via electron cyclotron maser emission.
The spectrum of HD 133880 matches a B8 subgiant, but with unusually strong absorption lines of some metals, making it a member of the chemically peculiar Ap/Bp star class. For this particular star, silicon lines at are notably strong. Its rotation rate is unusually fast for a star of this type.
In 1985, Christoffel Waelkens found that HD 133880 is a variable star with a period of days, varying by 0.15, 0.10 and 0.06 magnitudes in the U, B and V bands respectively. In 1986, the star was given the variable star designation HR Lupi. Later measurements of the period varied significantly, and can only be reconciled if the period varies in time.
In 1990, John Landstreet found that HD 133880 has a very strong. The radiation was found to vary by an order of magnitude as the star rotated, and had roughly 100 percent right circular polarization when the emission peaked.