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Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae

2009; Oxford University Press; Volume: 61; Issue: sp2 Linguagem: Inglês

10.1093/pasj/61.sp2.s395

2053-051X

Taichi Kato, Akira Imada, Makoto Uemura, Daisaku Nogami, Hiroyuki Maehara, Ryoko Ishioka, Hajime Baba, Katsura Matsumoto, H. Iwamatsu, Kaori Kubota, Kei Sugiyasu, Yuichi Soejima, Yuuki Moritani, Tomohito Ohshima, Hiroyuki Ohashi, Junpei Tanaka, Mahito Sasada, Akira Arai, Kazuhiro Nakajima, S. Kiyota, Kenji Tanabe, Kazuyoshi Imamura, Nanae Kunitomi, Kenji Kunihiro, Hiroki Taguchi, M. Koizumi, Norimi Yamada, Yuichi Nishi, Mayumi Kida, Sawa Tanaka, Rie Ueoka, Hideki Yasui, Koichi Maruoka, A. A. Henden, A. Oksanen, Marko Moilanen, Petri Tikkanen, M. Aho, Berto Monard, Hiroshi Itoh, Pavol A. Dubovský, Igor Kudzej, R. Dancikova, Tonny Vanmunster, Jochen Pietz, Greg Bolt, D. Boyd, Peter Nelson, Thomas Krajci, Lewis M. Cook, Ken’ichi Torii, D. Starkey, Jeremy Shears, Lasse-Teist Jensen, Gianluca Masi, T. Hynek, Р. Новак, R. Kocián, L. Král, H. Kučáková, M. Kolasa, Petr Šťastný, Bart Staels, Ian Miller, Y. Sano, Pierre de Ponthière, Atsushi Miyashita, Tim Crawford, Steve Brady, R. Santallo, Tom Richards, Brian Martin, D. Buczynski, M. Richmond, J. R. Kern, Stacey M. Davis, Dustin Crabtree, Kevin Beaulieu, Tracy C. Davis, Matt Aggleton, Etienne Morelle, Е. П. Павленко, M. Andreev, A. Baklanov, M. D. Koppelman, G. Billings, L’ubomír Urbančok, Y. Öǧmen, B. Heathcote, Tomás L. Gómez, I. B. Voloshina, A. Retter, K. Mularczyk, K. Złoczewski, A. Olech, P. Kędzierski, R. Pickard, Chris Stockdale, Jani Virtanen, Koichi Morikawa, Franz-Josef Hambsch, G. J. Garradd, C. Gualdoni, Keith Geary, Toshihiro Omodaka, Nobuyuki Sakai, R. Michel, A. A. Cárdenas, K. Gazeas, P. G. Niarchos, A. V. Yushchenko, F. Mallia, M. Fiaschi, Gerry A. Good, Stan Walker, Nick James, Ken-ichi Douzu, W. Mack Julian, N. Butterworth, S. Yu. Shugarov, I. M. Volkov, D. Chochol, Н. А. Катышева, Alexander E. Rosenbush, M. S. Khramtsova, P. Kehusmaa, M. Reszelski, J. Bedient, W. Liller, G. Pojmański, Mike Simonsen, Rod Stubbings, P. Schmeer, Eddy Muyllaert, Timo Kinnunen, G. Poyner, José Ripero, W. Kriebel,

Pulsars and Gravitational Waves Research

Abstract We systematically surveyed period variations of superhumps in SU UMa-type dwarf novae based on newly obtained data and past publications. In many systems, the evolution of the superhump period is found to be composed of three distinct stages: an early evolutionary stage with a longer superhump period, a middle stage with systematically varying periods, and a final stage with a shorter, stable superhump period. During the middle stage, many systems with superhump periods of less than 0.08 d show positive period derivatives. We present observational characteristics of these stages and give greatly improved statistics. Contrary to an earlier claim, we found no clear evidence for a variation of period derivatives among different superoutbursts of the same object. We present an interpretation that the lengthening of the superhump period is a result of the outward propagation of an eccentricity wave, which is limited by the radius near the tidal truncation. We interpret that late-stage superhumps are rejuvenated excitation of a 3:1 resonance when superhumps in the outer disk are effectively quenched. The general behavior of the period variation, particularly in systems with short orbital periods, appears to follow a scenario proposed in Kato, Maehara, and Monard (2008, PASJ, 60, L23). We also present an observational summary of WZ Sge-type dwarf novae. Many of them have shown long-enduring superhumps during a post-superoutburst stage having longer periods than those during the main superoutburst. The period derivatives in WZ Sge-type dwarf novae are found to be strongly correlated with the fractional superhump excess, or consequently with the mass ratio. WZ Sge-type dwarf novae with a long-lasting rebrightening or with multiple rebrightenings tend to have smaller period derivatives, and are excellent candidates for those systems around or after the period minimum of evolution of cataclysmic variables.