Quiescent photometric modulations of two low-inclination cataclysmic variables KZ Geminorum and TW Virginis

¹ Yunnan Observatories, Chinese Academy of Sciences, 396 Yangfangwang, Guandu District, 650216 Kunming, PR China
e-mail: zhibin_dai@ynao.ac.cn
² Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, 396 Yangfangwang, Guandu District, 650216 Kunming, PR China
³ Center for Astronomical Mega-Science, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, 100012 Beijing, PR China
⁴ University of Washington, Seattle, WA 98195, USA
⁵ Applied Sciences Department, Aqaba University College, Al-Balqa’ Applied University, PO Box 1199, 77110 Aqaba, Jordan
⁶ University of Notre Dame, Notre Dame, IN 46556, USA
⁷ Department of Physics, University College Cork, Cork, Ireland

Received: 3 June 2017
Accepted: 10 August 2017

Abstract

Aims. The quiescent periodic photometric modulations of two low-inclination cataclysmic variables observed in Kepler K2 Campaigns 0 and 1, KZ Gem and TW Vir, are investigated.

Methods. A phase-correcting method was successfully used to detect the orbital modulations of KZ Gem and TW Vir and improve their orbital periods. The light curve morphologies of both CVs were further analyzed by defining flux ratios and creating colormaps.

Results. KZ Gem shows ellipsoidal modulations with an orbital period of 0.22242(1) day, twice the period listed in the updated RK catalogue (Edition 7.24). With this newly determined period, KZ Gem is no longer a CV in the period gap, but a long-period CV. A part of the quiescent light curve of TW Vir that had the highest stability was used to deduce its improved orbital period of 0.182682(3) day. The flat patterns shown in the colormaps of the flux ratios for KZ Gem demonstrate the stability of their orbital modulations, while TW Vir show variable orbital modulations during the K2 datasets. In TW Vir, the single versus double-peaked nature of the quiescent orbital variations before and after superoutburst may be related to the effect of the superoutburst on the accretion disk.