Time Series Photometry of M67: W Ursae Majoris Systems, Blue Stragglers, and Related Systems

Abstract

We present an analysis of over 2200 V images taken on 14 nights at the Mount Laguna 1 m telescope of the open cluster M67. We show variability in the light curves of all four known W UMa variables on timescales ranging from a day to weeks. We have modeled the light curve of AH Cnc, and the total eclipses allow us to determine q = 0.16 and i = 86 deg. The position of this system near the turnoff of M67 makes it useful for constraining the turnoff mass for the cluster. We have also detected two unusual features in the light curve of AH Cnc that may be caused by prominences. We have also monitored cluster blue stragglers for variability. We present evidence hinting at low-level variations in the stragglers S752, S968, and S1263, and we place limits on the variability of a number of other cluster blue stragglers. Finally, we provide photometry of the subsubgiant branch star S1063 showing variability on timescales similar to the orbital period, while the red straggler S1040 shows evidence of an unexplained drop in brightness at phases corresponding to the passage of the white dwarf in front of the giant.