CBA Center for Backyard Astrophysics



Superhumps in Cataclysmic Binaries. VIII. V1159 Orionis

Joseph Patterson, Francisco Jablonski, Christopher Koen, Darragh O'Donoghue, and David Skillman

Publications of the Astronomical Society of the Pacific

December 1995, Volume 107, Page 1183

We report photometry of the cataclysmic variable V1159 Orionis for ~400 hours over 168 nights during 1992-4. The long-term light curves show that this is a dwarf nova of the SU UMa class, with normal outbursts recurring on a mean period of 4.0 days, and superoutbursts recurring on a period of 47.6 days. These periods wander slightly, as is typical of the class. High-speed photometry at minimum light, far from superoutbursts, reveals a weak photometric signal at 89.83 ± 0.10 min, which is presumably the underlying orbital period of the binary.

During superoutburst, large-amplitude superhumps are observed with P = 92.4 min. The superhumps appear very suddenly on the rising branch. In a few days they fade to a full amplitude of 0.1 mag and become more complex in waveform. However, they can be traced throughout the decline phase to quiescence, and even apparently succeed in enduring to the next normal eruption. In fact, we note the occasional existence of superhumps at essentially all phases of the eruption cycle--not merely at supermaxima, where they are very common and downright famous. The "positive" (P > Porb) superhumps resemble in detail the common superhumps seen in the best-known SU UMa stars, and can be reasonably interpreted as arising from an eccentric accretion disk with an advancing line of apsides. But additional subtle details are detected in V1159 Ori. In one superoutburst the frequencies of the high harmonics are slightly higher than expected, and in another they are far lower than expected. And on two occasions there appeared "negative" superhumps (P < Porb) with a period of 82.7 ± 0.2 min. We discuss these features in terms of the disk-precession model, but without any convincing resolution.

Two other periodic signals, of unknown origin, were detected: rapid oscillations ("DNOs") with a period increasing from 29 to 34 s over 7 days in mid-decline from a superoutburst; and a probable signal near 8 c/day, appearing mainly in quiescence.

Article

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Copyright © 1995 Astronomical Society of the Pacific.