Photometry of the three eclipsing novalike variables EC 21178-5417, GS Pav and V345 Pav

摘要

As part of a project to better characterize comparatively bright, yet littlestudied cataclysmic variables time resolved photometry of the three eclipsingnovalike variables EC 21178-5417, GS Pav und V345 Pav is presented. Previouslyknown orbital periods are significantly improved and long-term ephemeris arederived. Variations of eclipse profiles, occurring on time scales of days toweeks, are analyzed. Out of eclipse the light curves are characterized by lowscale flickering superposed on more gradual variations with amplitudes limitedto a few tenths of a magnitude and profiles which at least in EC 21178-5417 andGS Pav roughly follow the same pattern in all observed cycles. Additionally,signs for variations on the time scale of some tens of minutes are seen in GSPav, most clearly in two subsequent nights when in the first of these a signalwith a period of 15.7 min was observed over several hours. In the second nightvariations with twice this period were seen. While no additional insight couldbe gained on quasi periodic oscillations (QPOs) and dwarf nova oscillations inEC 21178-5417, previously detected by Warner et al. (2003), and while suchoscillations could not be found in V345 Pav, stacked power spectra of GS Pavclearly reveal the presence of QPOs over time intervals of several hours withperiods varying between 200 sec and 500 sec in that system.