BZ Camelopardalis during its 1999/2000 optical low state

Abstract

We report optical observations of the VY Scl star BZ Cam during its previous optical low state in 1999/2000. We find drastic variations in the line profiles. Narrow-band imaging observations show that its nebula extends farther than previously known and seems to be composed of two components. We determine the [O III] line intensity of BZ Cam's nebula to 4.8 10 -13 erg/cm 2 /s. We discover a proper motion of BZ Cam of 25 2 mas/yr which together with the systemic radial velocity yields a space velocity of 125 km s -1 . We re-interpret the nebula as being photo-ionized by hypothesized transient, luminous, supersoft X-ray emission during optical low states, and shaped by the transverse motion of BZ Cam.