Editing Variable star (section)

====Giants and supergiants====

Large stars lose their matter relatively easily. For this reason variability due to eruptions and mass loss is fairly common among giants and supergiants.

=====Luminous blue variables=====
{{Main|Luminous blue variable}}

Also known as the [[S Doradus]] variables, the most luminous stars known belong to this class. Examples include the [[hypergiant]]s [[Eta Carinae|η Carinae]] and [[P Cygni]]. They have permanent high mass loss, but at intervals of years internal pulsations cause the star to exceed its Eddington limit and the mass loss increases hugely. Visual brightness increases although the overall luminosity is largely unchanged. Giant eruptions observed in a few LBVs do increase the luminosity, so much so that they have been tagged [[supernova impostor]]s, and may be a different type of event.

=====Yellow hypergiants=====
{{Main|Yellow hypergiant}}

These massive evolved stars are unstable due to their high luminosity and position above the instability strip, and they exhibit slow but sometimes large photometric and spectroscopic changes due to high mass loss and occasional larger eruptions, combined with secular variation on an observable timescale. The best known example is [[Rho Cassiopeiae]].

=====R Coronae Borealis variables=====
{{Main|R Coronae Borealis variable}}

While classed as eruptive variables, these stars do not undergo periodic increases in brightness. Instead they spend most of their time at maximum brightness, but at irregular intervals they suddenly fade by 1–9 magnitudes (2.5 to 4000 times dimmer) before recovering to their initial brightness over months to years. Most are classified as yellow supergiants by luminosity, although they are actually post-AGB stars, but there are both red and blue giant R CrB stars. [[R Coronae Borealis]] (R CrB) is the prototype star. [[DY Persei variable]]s are a subclass of R CrB variables that have a periodic variability in addition to their eruptions.