The 2006 November outburst of EG Aquarii: the SU UMa nature revealed

Abstract

We report on time-resolved CCD photometry of the cataclysmic variable EG Aquarii during a 2006 November outburst. During the outburst, superhumps were unambiguously detected with a mean period of 0.078828(6) d, allowing for the first time to classify the object as an SU UMa-type dwarf nova. It also turned out that the outburst contained a precursor. At the end of the precursor, immature profiles of humps were observed. By a phase analysis of these humps, we interpreted the features as being superhumps. This is the second example that the superhumps were shown during a precursor. Near the maximum stage of the outburst, we discovered an abrupt shift of the superhump period by ∼ 0.002 d. After the supermaximum, the superhump period decreased at a rate of Ṗ / P = -8.2 × 10-5, which is typical for SU UMa-type dwarf novae. Although the outburst light curve was characteristic of SU UMa-type dwarf novae, long-term monitoring of the variable shows no outbursts over the past decade. We also comment on the basic properties of long period and inactive SU UMa-type dwarf novae. © 2008. Astronomical Society of Japan.