Long-period variable star

The descriptive term long-period variable (LPV) star refers to various groups of cool luminous pulsating variable stars.

Types of variation

The General Catalogue of Variable Stars does not define a long-period variable star type, although it does describe Mira variables as long-period variables. The term was first used in the 19th century, before more precise classifications of variable stars, to refer to a group that were known to vary on timescales typically hundreds of days. By the middle of the 20th century, long period variables were known to be cool giant stars. The relationship of Mira variables, semiregular variables, and other pulsating stars was being investigated and the term long period variable was generally restricted to the coolest pulsating stars, almost all Mira variables. Semiregular variables were considered intermediate between LPVs and Cepheids.

After the publication of the General Catalogue of Variable Stars, both Mira variables and semiregular variables, particularly those of type SRa, were often considered as long period variables. At its broadest, LPVs include Mira, semiregular, slow irregular variables, and OGLE small amplitude red giants (OSARGs), including both giant and supergiant stars. The OSARGs are generally not treated as LPVs, and many authors continue to use the term more restrictively to refer just to Mira and semiregular variables, or solely to Miras. The AAVSO LPV Section covers "Miras, Semiregulars, RV Tau and all your favorite red giants".