SCYON Abstract

Received on March 3 2006

BVI photometry of the very old open cluster Berkeley 17

AuthorsAngela Bragaglia(1), Monica Tosi(1), Gloria Andreuzzi(2,3), Gianni Marconi(4)
(1) INAF - Oss. Astron. Bologna
(2) Fundacion Galileo Galilei - INAF
(3) INAF - Oss. Astron. Roma
(4) ESO
Accepted byMonthly Notices of the Royal Astronomical Society
Links Berkeley 17


We have obtained BVI CCD imaging of Berkeley 17, an anticentre open cluster that competes with NGC 6791 as the oldest known open cluster. Using the synthetic colour magnitude diagrams (CMD) technique with three sets of evolutionary tracks we have determined that its age is 8.5 - 9.0 Gyr, it distance modulus is (m-M0) = 12.2, with a reddening of E(B-V) = 0.62 - 0.60. Differential reddening, if present, is at the 5% level. All these values have been obtained using models with metallicity about half of solar (Z=0.008 or Z=0.01 depending on the stellar evolution tracks), which allows us to reproduce the features of the cluster CMD better than other metallicities. Finally, from the analysis of a nearby comparison field we think to have intercepted a portion of the disrupting Canis Major dwarf galaxy.