100 research outputs found
Dwarf Novae in the Shortest Orbital Period Regime: I. A New Short Period Dwarf Nova, OT J055717+683226
We report the observation of a new dwarf nova, OT J055717+683226, during its
first-ever recorded superoutburst in December 2006. Our observation shows that
this object is an SU UMa-type dwarf nova having a very short superhump period
of 76.67+/- 0.03 min (0.05324+/-0.00002 d). The next superoutburst was observed
in March 2008. The recurrence time of superoutbursts (supercycle) is, hence,
estimated to be ~480 d. The supercycle is much shorter than those of WZ
Sge-type dwarf novae having supercycles of >~ 10 yr, which are a major
population of dwarf novae in the shortest orbital period regime (<~85 min).
Using a hierarchical cluster analysis, we identified seven groups of dwarf
novae in the shortest orbital period regime. We identified a small group of
objects that have short supercycles, small outburst amplitudes, and large
superhump period excesses, compared with those of WZ Sge stars. OT
J055717+683226 probably belongs to this group.Comment: 14 pages, 11 figures, accepted for publication in PAS
Optical and Near-Infrared Photometry of Nova V2362 Cyg : Rebrightening Event and Dust Formation
We present optical and near-infrared (NIR) photometry of a classical nova,
V2362 Cyg (= Nova Cygni 2006). V2362 Cyg experienced a peculiar rebrightening
with a long duration from 100 to 240 d after the maximum of the nova. Our
multicolor observation indicates an emergence of a pseudophotosphere with an
effective temperature of 9000 K at the rebrightening maximum. After the
rebrightening maximum, the object showed a slow fading homogeneously in all of
the used bands for one week. This implies that the fading just after the
rebrightening maximum ( less or equal 1 week ) was caused by a slowly shrinking
pseudophotosphere. Then, the NIR flux drastically increased, while the optical
flux steeply declined. The optical and NIR flux was consistent with blackbody
radiation with a temperature of 1500 K during this NIR rising phase. These
facts are likely to be explained by dust formation in the nova ejecta. Assuming
an optically thin case, we estimate the dust mass of 10^(-8) -- 10^(-10)
M_solar, which is less than those in typical dust-forming novae. These results
support the senario that a second, long-lasting outflow, which caused the
rebrightening, interacted with a fraction of the initial outflow and formed
dust grains.Comment: 6 pages, 4 figures, 2010, PASJ, 62, 1103--1108, in pres
Production and degradation of fluorescent dissolved organic matter in surface waters of the eastern north Atlantic ocean
The 2006 November outburst of EG Aquarii: the SU UMa nature revealed
We report time-resolved CCD photometry of the cataclysmic variable EG Aquarii
during the 2006 November outburst During the outburst, superhumps were
unambiguously detected with a mean period of 0.078828(6) days, firstly
classifying 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 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 days. After the supermaximum, the superhump period decreased at the rate
of =, 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 note on the basic properties of long period and inactive SU
UMa-type dwarf novae.Comment: 9 pages, 7 figures, accepted for PAS
- âŚ