AN Ursae Majoris

This is a single-lined spectroscopic binary system with a period of 1.92 hours in a close, circular orbit. The pair form an eclipsing binary system that decreases from magnitude 14.9 down to 20.2, once per orbit. This object, along with AM Herculis, define a class of cataclysmic variables known as polars. The pair consist of a low mass white dwarf with a strong magnetic field, interacting with a low–mass main sequence star that has filled its Roche lobe. Matter is being energetically accreted from the main sequence star onto one or both magnetic poles of the white dwarf star, producing emission lines in the spectrum. The magnetic field of the white dwarf has an estimated strength of 35.8 MG.