Superhumps and Accretion-Disk Precession in TT Arietis

David Skillman, David Harvey, Joseph Patterson, Jonathan Kemp, Lasse Jensen, Robert Fried, Gordon Garradd, Jerry Gunn, Liza van Zyl, Seiichiro Kiyota, Alon Retter, Tonny Vanmunster, and Paul Warhurst

Astrophysical Journal, Letters

10 August 1998, Volume 503, Page L67

We have been conducting a long-term (1988-1998) photometric study of the novalike variable TT Arietis. The main periodic signal in the star's light curve normally occurs at a period which varies but averages ~0.1329 d, about 3.5% shorter than the orbital period of the binary. In 1997 this signal disappeared, and was replaced by a stronger signal 8.5% longer than the orbital period. This new wave strongly resembles the "superhumps" commonly seen in SU UMa-type dwarf novae during superoutburst. In superhump parlance, we could say that a negative superhump was replaced by a positive superhump (P > P_orb). This could signify the development of an eccentric instability in the accretion disk. The two superhumps probably signify two types of disk precession: apsidal advance and nodal regression. TT Ari is an excellent candidate for observational studies which probe the origin of superhumps.

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Copyright © 1998 American Astronomical Society.