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arXiv · 0906.1810

Variable Stars in the Fornax dSph Galaxy. III. The Globular Cluster Fornax 5

Claudia Greco·Gisella Clementini·Marcio Catelan·Enrico V. Held·Ennio Poretti·Marco Gullieuszik·Marcella Maio·Armin Rest·Nathan De Lee·Horace A. Smith·Barton J. Pritzl
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Abstract

We present a new study of the variable star population in globular cluster 5 of the Fornax dwarf spheroidal galaxy, based on B and V time series photometry obtained with the MagIC camera of the 6.5 m Magellan Clay telescope and complementary HST archive data. Light curves and accurate periodicities were obtained for 30 RR Lyrae stars and 1 SX Phoenicis variable. The RR Lyrae sample includes 15 fundamental-mode pulsators, 13 first-overtone pulsators, 1 candidate double-mode pulsator and one RR Lyrae star with uncertain type classification. The average and minimum periods of the ab-type RR Lyrae stars, =0.590 days, P(ab,min)=0.53297 days, and the position in the horizontal branch type--metallicity plane, indicate that the cluster has Oosterhoff-intermediate properties, basically confirming previous indications by Mackey & Gilmore (2003b), although with some differences both in the period and type classification of individual variables. The average apparent magnitude of the Fornax 5 RR Lyrae stars is =21.35 +/- 0.02 mag (sigma=0.07 mag, average on 14 stars more likely belonging to the cluster, and having well sampled light curves). This value leads to a true distance modulus of mu0=20.76 +/- 0.07 (d=141.9 (+4.6;-4.5) kpc) if we adopt for the cluster the metal abundance by Buonanno et al. (1998; [Fe/H]=-2.20 +/- 0.20), or mu0=20.66 +/- 0.07 (d=135.5 (+4.4;-4.3) kpc), if we adopt Strader et al.'s (2003) metal abundance ([Fe/H]=-1.73 +/- 0.13).

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Claudia Greco, Gisella Clementini, Marcio Catelan, Enrico V. Held, Ennio Poretti, Marco Gullieuszik, Marcella Maio, Armin Rest, Nathan De Lee, Horace A. Smith, Barton J. Pritzl. 2009-06-09. Variable Stars in the Fornax dSph Galaxy. III. The Globular Cluster Fornax 5. https://doi.org/10.1088/0004-637x%2F701%2F2%2F1323

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