PM J03338+3320: Long-Period Superhumps in Growing Phase Following a Separate Precursor Outburst

• Published in: arXiv.org 2016-04
• Main Authors: Kato, Taichi, de Miguel, Enrique, Stein, William, Maeda, Yutaka, Littlefield, Colin, Kiyota, Seiichiro, Vanmunster, Tonny, Dvorak, Shawn, Sergey Yu Shugarov, Kalinicheva, Eugenia S, Pickard, Roger D, Kasai, Kiyoshi, Cook, Lewis M, Itoh, Hiroshi, Muyllaert, Eddy
• Format: Article
• Language: English
• Subjects: Cataclysmic variables; Orbits; Precursors; Superhumps (astronomy); Thermal instability; Tide prediction
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1604.01103

We observed the first-ever recorded outburst of PM J03338+3320, the cataclysmic variable selected by proper-motion survey. The outburst was composed of a precursor and the main superoutburst. The precursor outburst occurred at least 5 d before the maximum of the main superoutburst. Despite this separation, long-period superhumps were continuously seen between the precursor and main superoutburst. The period of these superhumps is longer than the orbital period by 6.0(1)% and can be interpreted to reflect the dynamical precession rate at the 3:1 resonance for a mass ratio of 0.172(4). These superhumps smoothly evolved into those in the main superoutburst. These observations provide the clearest evidence that the 3:1 resonance is triggered by the precursor outburst, even if it is well separated, and the resonance eventually causes the main superoutburst as predicted by the thermal-tidal instability model. The presence of superhumps well before the superoutburst cannot be explained by alternative models (the enhanced mass-transfer model and the pure thermal instability model) and the present observations give a clear support to the thermal-tidal instability model.