Survey of period variations of superhumps in SU UMa-type dwarf novae. VII. The seventh year (2014–2015)
2015
Continuing the project described by Kato et al. (2009, PASJ,
61, S395), we collected times of superhump maxima for 102 SU
UMa-type dwarf novae, observed mainly during the 2014-2015
season, and characterized these objects. Our project has
greatly improved the statistics of the distribution of orbital
periods, which is a good approximation of the distribution of
cataclysmic variables at the terminal evolutionary stage, and
has confirmed the presence of a periodminimum at a period of
0.053 d and a period spike just above this period. The number
density monotonically decreased toward the longer period and
there was no strong indication of a period gap. We detected
possible negative superhumps in Z Cha. It is possible that
normal outbursts are also suppressed by the presence of a disk
tilt in this system. There was no indication of enhanced
orbital humps just preceding the superoutburst, and this result
favors the thermal-tidal disk instability as the origin of
superoutbursts. We detected superhumps in three AM CVn-type
dwarf novae. Our observations and recent other detections
suggest that 8% of objects showing dwarf nova-type outbursts
are AM CVn-type objects. AM CVn-type objects and EI Psc-type
objects may be more abundant than previously recognized. OT
J213806, a WZ Sge-type object, exhibited remarkably different
features between the 2010 and 2014 superoutbursts. Although the
2014 superoutburst was much fainter, the plateau phase was
shorter than the 2010 one, and the course of the rebrightening
phase was similar. This object indicates that the O-C diagrams
of superhumps can indeed be variable, at least in WZ Sge-type
objects. Four deeply eclipsing SU UMa-type dwarf novae
(ASASSN-13cx, ASASSN-14ag, ASASSN-15bu, and NSV 4618) were
identified. We studied long-term trends in supercycles in MM
Hya and CY UMa and found systematic variations of supercycles
of similar to 20%.
- Correction
- Cite
- Save
- Machine Reading By IdeaReader
150
References
17
Citations
NaN
KQI