BV CCD Photometry of M71: Distance and Age

Abstract

We present BV CCD photometry of metal-rich globular cluster M71. Based on our color-magnitude diagram (CMD), we derive the distance to M71 using a sample of Hipparcos subdwarfs of similar metallicity. Our distance modulus is (m-M)V=13.46(± 0.17). CMD comparison was also made between M71 and 47 Tuc. We confirm that there exists a significant age difference(> 2 billion years) in spite of their similarity in metallicity.

Keywords

• globular cluster
• M71
• CCD photometry
• color-magnitude diagram
• distance
• relative age