Z Andromedae

The brightness of those stars vary over time, showing a quiescent, more stable phase and then an active one with a more pronounced variability and stronger brightening and/or dimming.

[10] The evolved red giant star is losing mass, since radiation pressure overcomes the low gravity on the surface.

[13] During the quiescent phase, most of the white dwarf luminosity comes from stable hydrogen burning on its surface, and photons emitted this way ionize the wind of the red giant which causes nebular emission.

[7] In the quiescent phase, the brightness of Z Andromedae is modulated by the orbital period of the system, and can reach a magnitude of mv = 11.3 at minimum.

[8][2][7] Z Andromedae started an unusually long active phase in September 2000, brightening by several magnitudes multiple times over at least a decade.

During the outbursts, irregular brightness variations (up to 0.065 magnitudes) were observed at timescales shorter than a day, interpreted as warping in the accretion disk.

Early spectra during a bright period, showing only emission lines against a red continuum, were interpreted as a star embedded in dense nebulosity.

Here the luminosity class of III is for a normal giant star, and the peculiarity codes eq indicate emission lines with P Cygni profiles.