HD 133880, also known as HR 5624 and HR Lupi, is a

Bp star Ap and Bp stars are chemically peculiar stars (hence the "p") of spectral types A and B which show overabundances of some metals, such as strontium, chromium and europium. In addition, larger overabundances are often seen in praseodymium and neodym ...

about 340

light year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s from the Earth, in the constellation

Lupus Lupus, technically known as systemic lupus erythematosus (SLE), is an autoimmune disease in which the body's immune system mistakenly attacks healthy tissue in many parts of the body. Symptoms vary among people and may be mild to severe. Comm ...

. It is a 5th

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

star, and will be faintly visible to the naked eye of an observer far from

city lights ''City Lights'' is a 1931 American silent romantic comedy film written, produced, directed by, and starring Charlie Chaplin. The story follows the misadventures of Chaplin's Tramp as he falls in love with a blind girl (Virginia Cherrill) and ...

. It is an

SX Arietis variable SX Arietis variables are a class of variable stars. They are generally B-type main sequence stars of spectral types B0p to B9p— high-temperature analogues of Alpha2 Canum Venaticorum variables—and exhibit strong magnetic fields and intense He& ...

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 In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Her ...

lifetime. It is one of the few stars known to produce coherent pulsed radio radiation via electron cyclotron maser emission. The

spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors i ...

of HD 133880 matches a B8

subgiant A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution of ...

, but with unusually strong

absorption line A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to iden ...

s 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 (several k G)

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

, with the unusual property that its

quadrupole A quadrupole or quadrapole is one of a sequence of configurations of things like electric charge or current, or gravitational mass that can exist in ideal form, but it is usually just part of a multipole expansion of a more complex structure refl ...

term is stronger than the

dipole In physics, a dipole () is an electromagnetic phenomenon which occurs in two ways: *An electric dipole deals with the separation of the positive and negative electric charges found in any electromagnetic system. A simple example of this system i ...

term. However a study in 2017 found the magnetic field was better described as a distorted asymmetric dipole, with a maximum strength of 12 kG, and an average strength of 4 kG. Much of the research interest in HD 133880 arises from its radio emissions. Jeremy Lim ''et al.'' observed the star with the

Australia Telescope Compact Array The Australia Telescope Compact Array (ATCA) is a radio telescope operated by CSIRO at the Paul Wild Observatory, twenty five kilometres (16 mi) west of the town of Narrabri in New South Wales, Australia. Its opening ceremony took place on ...

in 1995, and found that because the star's magnetic and rotation axes are not aligned, the 6 cm wavelength radiation they measured showed variation in both strength and polarization as the star rotated. In 2018 Barnali Das ''et al.'' detected electron

cyclotron A cyclotron is a type of particle accelerator invented by Ernest O. Lawrence in 1929–1930 at the University of California, Berkeley, and patented in 1932. Lawrence, Ernest O. ''Method and apparatus for the acceleration of ions'', filed: Janu ...

maser A maser (, an acronym for microwave amplification by stimulated emission of radiation) is a device that produces coherent electromagnetic waves through amplification by stimulated emission. The first maser was built by Charles H. Townes, Ja ...

emission from the star at 610 MHz, using the

GMRT The Giant Metrewave Radio Telescope (GMRT), located near Pune, Junnar, near Narayangaon at khodad in India, is an array of thirty fully steerable parabolic radio telescopes of 45 metre diameter, observing at metre wavelengths. It is operated by t ...

. HD 133880 was the second star found to radiate in this way (after CU Virginis). The radiation was found to vary by an order of magnitude as the star rotated, and had roughly 100 percent right

circular polarization In electrodynamics, circular polarization of an electromagnetic wave is a polarization state in which, at each point, the electromagnetic field of the wave has a constant magnitude and is rotating at a constant rate in a plane perpendicular to t ...

when the emission peaked.

References

{{DEFAULTSORT:HD 133880 SX Arietis variables Lupus (constellation) 74066 133880 Lupi, HR 5624 B-type subgiants Ap stars