The eclipsing post-common envelope binary CSS21055: a white dwarf with a probable brown-dwarf companion

We report photometric observations of the eclipsing close binary CSS21055 (SDSS J141126+200911) that strongly suggest that the companion to the carbon-oxygen white dwarf is a brown dwarf with a mass between 0.030 and 0.074 M ⊙ . The measured orbital period is 121.73 min and the totality of the eclipse lasts 125 s. If confirmed, CSS21055 would be the first detached eclipsing WD+BD binary. Spectroscopy in the eclipse could provide information about the companion’s evolutionary state and atmospheric structure.