The extrinsic classification refers to eclipsing, rotating, and microlensing variable stars, all of which have flux variations as a result of external stellar factors.
Variable Stars and Collaboration with the AAVSO
An international non-profit encompassing both amateur and professional astronomers, the American Association of Variable Star Observers (AAVSO) provides assistance with stellar activity monitoring, statistical analysis, and many more key components of astronomical research.
Variable Stars and their Relation to Stellar Evolution
This video covers a high level view of the stellar life cycle as relating to variable stars, discussing pre-main sequence, the main sequence, after the main sequence, and after the AGB
Variable Star Overview
Variable stars have a varying light output as seen from our vantage point; their light output can be affected by extrinsic and intrinsic variables.
The group of Intrinsic variable stars is classified based on internal stellar structure causing the changes to the star, and thus the variability to their flux. It covers most of the variable star classes: Eruptive, Cataclysmic, and Pulsation.