Old open clusters
(age ~ Gyrs) are valuable representatives of the early Galactic disk
population. In addition to being relatively richer and denser than their
younger counterparts, they provide an excellent environment for the study of
variables among stars of known age, distance and metallicity. Our primary interest in them originate in
computer N-body simulations that predict the formation of one or two CVs in rich (~10^5 stars) open clusters
after only 1Gyr of cluster evolution (Hurley & Shara 2002). On the other hand, only three CVs are currently
known in all open clusters. Systematic searches can eventually put constraints on the existing CV formation ege
and evolution scenarios. Thus, we have initiated a CV search in old open clusters as a part of WOCS. A
secondary goal is to reveal the variable star population of the clusters.
This is one of the images I took with the WTTM
imager (withought using WTTM though) on March 23, 2003. The seeing was
0.3'' in z, in a moonless, perfectly clear night! Only two colors were
obtained (z and B); the processing was done by George Jacoby. The result
is fabulous! A high resolution version of it can be found at the NOAO
image gallery:
This is one of the WOCS clusters I was studying for variability. This
picture was taken by my REU students and myself during the summer 2003
observing run with the WIYN 0.9m/S2KB CCD at Kitt Peak Arizona.
