CBA Center for Backyard Astrophysics

Superhumps in Cataclysmic Binaries. XVI. DI Ursae Majoris

Robert Fried, Jonathan Kemp, Joseph Patterson, David Skillman, Alon Retter, Elia Leibowitz, and Elena Pavlenko

Publications of the Astronomical Society of the Pacific

October 1999, Volume 111, Page 1275

We report photometry of the dwarf nova DI Ursae Majoris during 1997-1998. The star shows an orbital light curve at quiescence with a period of 0.054564(1) days. During superoutburst, it flashes superhumps with a period of 0.05529(5) days. The superhump period excess of 1.3% is quite low among cataclysmic variables, suggesting a weak perturbation on the accretion disk and therefore a secondary of very low mass. But other stars of low period excess are rare eruptors, whereas DI UMa is extremely active with normal outbursts every 8 days and superoutbursts every 30-45 days. This is puzzling. We speculate that the binary really does have a secondary of anomalously low mass but is presently in a high state of a mass-transfer cycle.



Copyright © 1999 Astronomical Society of the Pacific.