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Discovery of a Variable Star Population in NGC 2808
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Astronomy Astrophysics manuscript no. 0944Catelan February 2, 2008
(DOI: will be inserted by hand later)
Research Note
Discovery of a Variable Star Population in NGC 2808
T. Michael Corwin
1,?
, M. Catelan
2 ,?
, J. Borissova
2 ,?
, and H. A. Smith
3
1
Department of Physics, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
e-mail: mcorwin@uncc.edu
2
Pontificia Universidad Cato?lica de Chile, Departamento de Astronom??a y Astrof??sica,
Av. Vicun?a Mackenna 4860, 782-0436 Macul, Santiago, Chile
e-mail: mcatelan, jborisso, ajd@astro.puc.cl
3
Dept. of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA
e-mail: smith@pa.msu.edu
Received; accepted
Abstract. We have applied the image subtraction method to images of the peculiar, bimodal-horizontal branch globular cluster
NGC 2808, taken over a total of six nights over a range of five months. As a result, we have found, for the first time, a sizeable
population of variable stars in the crowded inner regions of the cluster, thus raising the known RR Lyrae population in the
cluster to a total of 18 stars. In addition, an eclipsing binary and two other variables with periods longer than 1 day were also
found. Periods, positions and (differential) light curves are provided for all the detected variables. The Oosterhoff classification
of NGC 2808, which has recently been associated with a previously unknown dwarf galaxy in Canis Major, is briefly discussed.
Key words. Galaxy: globular clusters: individual: NGC 2808 – stars: horizontal-branch – stars: variables: RR Lyr
1. Introduction
Adequate interpretation of the color-magnitude diagrams of globular clusters (GCs) in terms of age, metallicity and other evo-
lutionary parameters is one of the most important goals of stellar astrophysics, constraining both the formation history of the
Galaxy and the age of the Universe. Yet, there are still several open problems in t
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