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YZ Cancri

YZ Cnc is one of the more popular of the SU Ursae Majoris subtype dwarf novae.  One of the defining characteristics of the SU UMa (or "UGSU") class is the occurrence of occasional superoutbursts that rise higher and last longer than normal outbursts that characterize all dwarf novae.  YZ Cnc undergoes normal outbursts that reach magnitude
 12 or so and last for perhaps 4 or 5 days.  But then it also undergoes superoutbursts that reach 11th magnitude and last on the order of 20 days.  YZ Cnc also shows another common characteristic with the SU UMa stars -- superhumps.  These brightness variations have periods a few percent longer than the orbital period, and are caused by precession of the accretion disk; the superhump period is a beat period between the orbital period and the precession period.

This stretch of data from early 2003 shows the fast and frequent normal outbursts mixed in among two superoutbursts starting around 2452665 and 2452765.

For more information visit: /vsots_suuma
Prepared By: Matthew Templeton
AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484