Long period variable

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A long period variable (LPV) is a type of variable star in which variations in brightness occur over long timescales of months or years. Long period variables are giant stars and brighter, from spectral class F and redwards, but most are red giants and AGB giants, meaning spectral class M, S or C. They are usually deep orange or red.

The following well defined variable star classes use to be counted into the LPV category:

Mira variables, long rather regular pulsation periods in the range between 80 to 1000 days and grand light variations, from 2.5 magnitudes up to 11,
semiregular variables, the periods in the same range as Miras, but lower amplitude and often irregularities that makes the period determination hard,
slow irregular variables, stars similar to the semiregulars, but whose period cannot be determined, because of the irregularity of the light change.