SCYON Abstract

Received on September 28 2006

Deep HST Photometry of NGC 6388: Age and Horizontal Branch Luminosity

Authors	M. Catelan (¹), P.B. Stetson (²), B.J. Pritzl (³), H.A. Smith (⁴), K. Kinemuchi (⁵), A.C. Layden (⁶), A.V. Sweigart (⁷), and R.M. Rich (⁸)
Affiliation	(¹) PUC-Chile (²) DAO-NRC (³) Macalester (⁴) Michigan State (⁵) Wyoming (⁶) Bowling Green (⁷) NASA-GSFC (⁸) UCLA
To appear in	ApJ Letters
Contact	mcatelan@astro.puc.cl
URL	http://xxx.lanl.gov/abs/astro-ph/0609727
Links

Abstract

Using the Hubble Space Telescope, we have obtained the first color-magnitude diagram (CMD) to reach the main-sequence turnoff of the Galactic globular cluster NGC 6388. From a comparison between the cluster CMD and 47 Tucanae's, we find that the bulk of the stars in these two clusters have nearly the same age and chemical composition. On the other hand, our results indicate that the blue horizontal branch and RR Lyrae components in NGC 6388 are intrinsically overluminous, which must be due to one or more, still undetermined, non-canonical second parameter(s) affecting a relatively minor fraction of the stars in NGC 6388.