522 research outputs found
Discovery of Extremely Large-Amplitude Quasi-Periodic Photometric Variability in WC9-Type Wolf-Rayet Binary, WR 104
We discovered that the Wolf-Rayet (WR)+OB star binary, WR 104, renowned for
its associated "dusty pinwheel nebula" recently spatially resolved with
infrared interferometry, exhibits strong quasi-periodic optical variations with
a full amplitude of 2.7 mag. Such a large-amplitude, continuous variation has
been unprecedented in a WR star. The optical quasi-period (~241 d) is in almost
perfect agreement with the interferometric period (243.5+/-3 d). The remarkable
agreement of the dominant period in optical variability with the orbital period
supports that the strongly varying dust obscuration is physically related to
the binary motion, rather than sporadic dust-forming episodes. Considering the
low orbital inclination (11+/-7 deg) and the nearly circular orbit inferred
from the interferometric observations, the strongly variable line-of-sight
extinction suggests that the highly structured extinction can be being formed
via an ejection of dust in the direction of the binary rotation axis. Another
viable explanation is that the three-dimensional structure of the shock front,
itself is the obscuring body. Depending on the geometry, the dusty shock front
near the conjunction phase of the binary can completely obscure the inner
WR-star wind and the OB star, which can explain the amplitude of optical fading
and the past observation of remarkable spectral variation.Comment: 5 pages, 4 figures, to appear in PASJ (Letters), using an alternative
style fil
Deep Transient Optical Fading in the WC9 Star WR 106
We discovered that the WR9-type star WR 106 (HDE 313643) underwent a deep
episodic fading in 2000. The depth of the fading (dV ~ 2.9 mag) surpassed those
of all known similar "eclipse-like" fadings in WR stars. This fading episode
was likely to be produced by a line-of-sight episodic dust formation rather
than a periodic enhancement of dust production in the WR-star wind during the
passage of the companion star though an elliptical orbit. The overall 2000
episode was composed of at least two distinct fadings. These individual fadings
seem to more support that the initial dust formation triggered a second dust
formation, or that the two independent dust formations occurred by the same
triggering mechanism rather than a stepwise dust formation. We also discuss on
phenomenological similarity of the present fading with the double fading of R
CrB observed in 1999-2000.Comment: 3 pages, 4 figures, to appear in Astron. Astrophys. (Letters
Reliable Authentication Method by Using Cellular Phones in Web Based Training
Articles are the intellectual property of the author. The Creative Commons copyright permits copy or dissemination for education or non-profit purposes so long as author and title of the article are included with title, volume, number and URL for the Journal.Institutions of higher education that offer credits through distance learning using web based training (WBT) have increased recently. In these situations, an authentication model using the IDpassword pair is generally used. However, this authentication model cannot prevent “identity theft” effectively. We propose a new authentication method that solves this problem by using cellular phones as an authentication token. The authentication accuracy is expected to be improved by combining the ID-password pair with the subscriber ID of cellular phones. We realized a prototype system and prepared a questionnaire in order to validate the effectiveness of our proposed method, and as a result, we demonstrated the effectiveness and realizability of our method.ArticleInternational Journal of Instructional Technology and Distance Learning. 3(12):35-45 (2006)journal articl
Reliable Authentication Method by Using Cellular Phones in WBT
Institutions of higher education that give the credits by distance learning using WBT have increased recently. In these situations, the authentication model by (ID, password) pair is general. However, this authentication model cannot prevent “Identity theft” effectively. In this paper, we propose a new authentication model to solve this problem by using cellular phones.ArticleProceedings of the International Conference on Networking, International Conference on Systems and International Conference on Mobile Communications and Learning Technologies (ICNICONSMCL’06)conference pape
Instability of Magnons in Two-dimensional Antiferromagnet at High Magnetic Fields
Spin dynamics of the square lattice Heisenberg antiferromagnet, \BaMnGeO, is
studied by a combination of bulk measurements, neutron diffraction, and
inelastic neutron scattering techniques. Easy plane type antiferromagnetic
order is identified at K. The exchange interactions are estimated
as = 27.8(3)eV and = 1.0(1) eV, and the saturation
field is 9.75 T. Magnetic excitation measurements with high
experimental resolution setup by triple axis neutron spectrometer reveals the
instability of one magnon excitation in the field range of .Comment: 5 pgase, 5 figuers, to be published in PRB R
V463 Scuti (Nova Sct 2000): Rapidly Evolving Nova with a Prominent Premaximum Halt
We summarize photometric and spectroscopic observations of V463 Sct (Nova Sct
2000), which was originally thought to be a red variable. The spectrum taken on
2000 March 16.81 UT showed prominent emission lines with a FHWM of 990 km/s (H
alpha). The light curve shows a conspicuous premaximum halt lasting at least
for 24 d, and a late-phase flare-like maximum. The nova then started rapidly
fading at a rate corresponding to t2 = 15 +/- 3 d. Long premaximum halts have
been considered as a unique character of the "slowest" novae. The present
observation, however, suggests that the long premaximum halts are not a unique
character of the slowest novae, but a more general phenomenon spreading over a
wider range of nova speed classes than has been previously believed. A recent
interpretation of premaximum halts requires that the conditions of
thermonuclear runaway was only marginally satisfied. Since such conditions are
more difficult to meet in rapidly evolving novae, V463 Sct would provide an
unique opportunity in testing this interpretation. The early post-outburst
spectrum showed co-existence of Fe II lines and some forbidden lines, which
suggests that substantial amount of material may have been ejected before the
observed optical maximum. The impact of the modern global network (VSNET) on
confirmatory processes of transient objects is briefly discussed.Comment: 7 pages, 4 figures, accepted for publication in Publ. Astron. Soc.
Japa
Discovery of a New Deeply Eclipsing SU UMa-Type Dwarf Nova, IY UMa (= TmzV85)
We discovered a new deeply eclipsing SU UMa-type dwarf nova, IY UMa, which
experienced a superoutburst in 2000 January. Our monitoring revealed two
distinct outbursts, which suggest a superoutburst interval of ~800 d, or its
half, and an outburst amplitude of 5.4 mag. From time-series photometry during
the superoutburst, we determined a superhump and orbital period of 0.07588 d
and 0.0739132 d, respectively.Comment: 5 pages, 3 figures, accepted by PASJ lette
Geriatric Medical Care in the Area of the Regional Association Westphalia-Lippe Dokkyo Medical University 5th grade
Dokkyo Medical University 5th YearDokkyo Medical University 5th YearDokkyo Medical University 5th YearDokkyo Medical University 5th YearDokkyo Medical University 5th YearDokkyo Medical University 5th YearDokkyo MedicalUniversity, Division of Languages and HumanitiesWestphalian Wilhelms University, IfASWestphalian Wilhelms University, General PracticeKlinik Maria Frieden, Abt. f. GeriatrieDokkyo Medical University, Office for German-Japanese CooperationDokkyo Medical University, Office for German-Japanese Cooperatio
Measuring the frequency of a Sr optical lattice clock using a 120-km coherent optical transfer
We demonstrate a precision frequency measurement using a phase-stabilized
120-km optical fiber link over a physical distance of 50 km. The transition
frequency of the 87Sr optical lattice clock at the University of Tokyo is
measured to be 429228004229874.1(2.4) Hz referenced to international atomic
time (TAI). The measured frequency agrees with results obtained in Boulder and
Paris at a 6*10^-16 fractional level, which matches the current best
evaluations of Cs primary frequency standards. The results demonstrate the
excellent functions of the intercity optical fibre link, and the great
potential of optical lattice clocks for use in the redefinition of the second.Comment: 14 pages, 3 figure
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