Open AccessOld open clusters: the interesting case of Berkeley 21
Author(s) -
Tosi M.,
Pulone L.,
Marconi G.,
Bragaglia A.
Publication year - 1998
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1998.01812.x
Subject(s) - physics , distance modulus , open cluster , metallicity , photometry (optics) , astrophysics , cluster (spacecraft) , astronomy , galaxy groups and clusters , galaxy cluster , galaxy , stars , computer science , programming language
We present CCD BVI photometry of the old open cluster Berkeley 21, one of the most distant clusters in the Galactic anticentre direction, and possibly the lowest metallicity object in the open clusters sample. Its position and metal abundance make it very important for the study of the Galactic disc. Using the synthetic colour–magnitude diagram method, we estimate values for the distance modulus ( m − M ) 0 = 13.4–13.6, reddening E ( B − V ) = 0.74–0.78 (with possible differential absorption), and age = 2.2–2.5 Gyr.