MWC560—a unique astrophysical object

DESPITE its interesting behaviour^1,2, the object MWC560 has been little studied since its discovery 50 years ago during the Mount Wilson Observatory Hα emission-line surveys³. To rectify this situation we have made systematic spectral and photometric observations of this star. Spectra of the hydrogen absorption Balmer lines show remarkable variability: they indicate that some components have radial velocities as large as -6,000 km s^-1, and the profiles are complex, showing pronounced variability on times-cales of a few days. Photometric observations show that the V-band brightness of the star has risen by about three magnitudes over the past 20 years; during our own observations, this brightness was seen to change by a few tenths of a magnitude. We speculate that MWC560 may be a binary system containing a red giant and a compact companion—possibly a white dwarf—and exhibiting jet-like ejections along the line of sight⁴.