Optical and Near-Infrared Photometric Observation during the Superoutburst of the WZ Sge-Type Dwarf Nova, V455 Andromedae

Publications- Astronomical Society of Japan (Impact Factor: 2.44). 08/2009; DOI: 10.1093/pasj/61.5.1081
Source: arXiv

ABSTRACT We report on optical and infrared photometric observations of a WZ Sge-type dwarf nova, V455 And during a superoutburst in 2007. These observations were performed with the KANATA (V, J, and K_s bands) and MITSuME (g', Rc, and Ic bands) telescopes. Our 6-band simultaneous observations allowed us to investigate the temporal variation of the temperature and the size of the emitting region associated with the superoutburst and short-term modulations, such as early and ordinary superhumps. A hot (>11000 K) accretion disk suddenly disappeared when the superoutburst finished, while blackbody emission, probably from the disk, still remained dominant in the optical region with a moderately high temperature (~8000 K). This indicates that a substantial amount of gas was stored in the disk even after the outburst. This remnant matter may be a sign of an expected mass-reservoir which can trigger echo outbursts observed in several WZ Sge stars. The color variation associated with superhumps indicates that viscous heating in a superhump source stopped on the way to the superhump maximum, and a subsequent expansion of a low-temperature region made the maximum. The color variation of early superhumps was totally different from that of superhumps: the object was bluest at the early superhump minimum. The temperature of the early superhump light source was lower than that of an underlying component, indicating that the early superhump light source was a vertically expanded low-temperature region at the outermost part of the disk. Comment: 14 pages, 12 figures, PASJ accepted

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    Journal of the British Astronomical Association. 01/1996; 106:223.
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    ABSTRACT: A dwarf nova HV Vir was observed photometrically for eight nights during the outburst in 1992 April - May. The star showed two distinct types of periodic variation: (1) 82.20-min (0.05708 d) double-humped variation with decaying amplitudes during the early stage of the outburst, and (2) 83.80-min (0.05820 d) superhumps in later stages. We attributed the former to "early superhumps", which are only seen in the earliest stage of WZ Sge-type outbursts. The superhump period and evolution of the superhumps, together with general characteristics of the light curve, make HV Vir a typical WZ Sge-type dwarf nova. HV Vir also showed a large increase of the superhump period during the superoutburst. Upon the recognition of the WZ Sge-type nature of an object previously considered as a nova, we present a comprehensive list of candidates for WZ Sge-type dwarf novae, and related systems.
    Publications- Astronomical Society of Japan 11/2001; · 2.44 Impact Factor
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    ABSTRACT: We report on time-resolved photometric observations of the WZ Sge-type dwarf nova, EG Cnc (Huruhata's variable, see also, during its superoutburst in 1996-1997. EG Cnc, after the main superoutburst accompanied with 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 the superhumps observed during the rebrightening stage and the fading tail are a "remnant" of usual superhumps, and are not newly triggered by rebrightenings. By 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 considerable amount of remnant matter behind the cooling front in the outer accretion disk, even after the main superoutburst. We consider the 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.
    Publications- Astronomical Society of Japan 11/2003; · 2.44 Impact Factor


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