SCYON Abstract

Received on March 9 2010

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

AuthorsIain McDonald (1,2), Jacco Th. van Loon (1), Andrea K. Dupree (3), and Martha L. Boyer (4)
Affiliation(1) Astrophysics Group, Lennard-Jones Laboratories, Keele University, Staffordshire, ST5 5BG, UK
(2) Jodrell Bank Centre for Astrophysics, Alan Turing Building, Manchester University, M13 9PL, UK
(3) Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
(4) STScI, 3700 San Martin Drive, Baltimore, MD 21218, USA
Accepted byMonthly Notices of the Royal Astronomical Society
Contactiain@astro.keele.ac.uk
URLhttp://arxiv.org/abs/1003.1498
Links

Abstract

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 multi-colour optical photometry from the 0.6-m Keele Thornton and 2-m Liverpool Telescopes. Variability of delta-V ~ 0.15 mag is detected in K757 and K825 over unusually-long timescales 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 intra-cluster medium of this cluster.