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We present a search for long‐period variable (LPV) stars among giant branch stars in M15 which, at [Fe/H]∼−2.3, is one of the most metal‐poor Galactic globular clusters. We use multicolour optical photometry from the 0.6‐m Keele Thornton and 2‐m Liverpool Telescopes. Variability of  δ V ∼ 0.15  mag is detected in K757 and K825 over unusually long time‐scales of nearly a year, making them the most metal‐poor LPVs found in a Galactic globular cluster. K825 is placed on the long secondary period sequence, identified for metal‐rich LPVs, though no primary period is detectable. We discuss this variability in the context of dust production and stellar evolution at low metallicity, using additional spectra from the 6.5‐m Magellan (Las Campanas) telescope. A lack of dust production, despite the presence of gaseous mass loss raises questions about the production of dust and the intracluster medium of this cluster.

Discovery of long‐period variable stars in the very metal‐poor globular cluster M15