Z UMi

Z UMi is a fairly recent addition to the RCB family, only being confirmed as a member of that class since 1992.  The light curve profile suggests this this object could well be a member of the DYPER sub-group of RCB stars.

CCD observations obtained with the Bradford Robotic Telescope,

Comparison chart showing the length and depth of all previously observed minima in Z UMi.  Data points taken at 10d intervals.  The large gap in the 2007-2008 minimum equates to down time of the Bradford Robotic Telescope, just as Z UMi began to recover from it's historical low state.

The graph reveals that the first two magnitudes drop at a constant rate of 20 days.  The recovery is also constant with a 40 day period to regain the final two magnitudes to maximum.  Only the length of time spent at minimum varies.  The longer the minimum of course, the deeper the magnitude!  

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