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Unveiling the Core of M 15 in the Far-Ultraviolet

Published online by Cambridge University Press:  01 September 2007

A. Dieball ,
C. Knigge ,
D. R. Zurek ,
M. M. Shara ,
K. S. Long ,
P. A. Charles  and
D. Hannikainen
A. Dieball
Affiliation:
Department of Physics and Astronomy, University Southampton, SO17 1BJ, UK email: andrea@astro.soton.ac.uk
C. Knigge
Affiliation:
Department of Physics and Astronomy, University Southampton, SO17 1BJ, UK email: andrea@astro.soton.ac.uk
D. R. Zurek
Affiliation:
Department of Astrophysics, American Museum of Natural History, New York, NY 10024
M. M. Shara
Affiliation:
Department of Astrophysics, American Museum of Natural History, New York, NY 10024
K. S. Long
Affiliation:
Space Telescope Science Institute, Baltimore, MD 21218
P. A. Charles
Affiliation:
South African Astronomical Observatory, PO Box 9, Observatory, 7935, South Africa
D. Hannikainen
Affiliation:
University of Helsinki, P.O. Box 14, SF-00014 Helsinki, Finland
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Abstract

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We present an analysis of our deep far- (FUV) and near-ultraviolet (NUV) photometry of the core region of the dense globular cluster M 15. Our FUV-NUV colour-magnitude diagram (CMD) is the deepest one presented for a globular cluster so far, and shows all hot stellar populations expected in a globular cluster, such as horizontal branch stars, blue stragglers, white dwarfs, cataclysmic variables and even main sequence stars. The main sequence turn-off is clearly visible and the main sequence stars form a prominent track that extends at least two magnitudes below the main sequence turn-off. We compare and discuss the radial distribution of the various stellar populations that show up in the FUV. We search for variability amongst our FUV sources and tentatively classify our variable candidates based on an analysis of the UV colours and variability properties. We find that RR Lyraes, Cepheids, and SX Phoenicis exhibit massive variability amplitudes in this waveband (several mags).

Keywords

globular clusters: individual (M 15)stars: cataclysmic variableswhite dwarfsstars: variables: otherultraviolet: starsblue stragglersbinaries: close
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S246: Dynamical Evolution of Dense Stellar Systems , September 2007 , pp. 361 - 362
Copyright
Copyright © International Astronomical Union 2008