Superhumps and Repetitive Rebrightenings of the WZ Sge-Type Dwarf Nova, EG Cancri
Abstract
We report on time-resolved photometric observations of the WZ Sge-type dwarf nova, EG Cnc (Huruhata's variable), during its superoutburst in 1996-1997. EG Cnc, after the main superoutburst accompanied by the development of superhumps typical of a WZ Sge-type dwarf nova, exhibited a series of six major rebrightenings. During these rebrightenings and the following long fading tail, EG Cnc persistently showed superhumps having a period equal to the superhump period observed during the main superoutburst. The persistent superhumps had a constant superhump flux with respect to the rebrightening phase. These findings suggest that the superhumps observed during the rebrightening stage and the fading tail are a ``remnant'' of the usual superhumps, and are not newly triggered by rebrightenings. By a comparison with the 1977 outburst of this object and outbursts of other WZ Sge-type dwarf novae, we propose an activity sequence of WZ Sge-type superoutbursts, in which the current outburst of EG Cnc is placed between a single-rebrightening event and distinct outbursts separated by a dip. The post-superoutburst behavior of WZ Sge-type dwarf novae can be understood in the presence of a considerable amount of remnant matter behind the cooling front in the outer accretion disk, even after the main superoutburst. We consider that a premature quenching of the hot state due to the weak tidal effect under the extreme mass ratio of the WZ Sge-type binary is responsible for the origin of the remnant mass.
- Publication:
-
Publications of the Astronomical Society of Japan
- Pub Date:
- March 2004
- DOI:
- 10.1093/pasj/56.sp1.S109
- arXiv:
- arXiv:astro-ph/0310426
- Bibcode:
- 2004PASJ...56S.109K
- Keywords:
-
- accretion;
- accretion disks;
- stars: dwarf novae;
- stars: individual (EG Cancri);
- stars: novae;
- cataclysmic variables;
- Astrophysics
- E-Print:
- 16 pages, 15 figures, to appear in PASJ (special issue on VSNET), for more information, see http://www.kusastro.kyoto-u.ac.jp/vsnet/