895 research outputs found
The Light and Period Variations of the Eclipsing Binary BX Draconis
New CCD photometric observations of BX Dra were obtained for 26 nights from
2009 April to 2010 June. The long-term photometric behaviors of the system are
presented from detailed studies of the period and light variations, based on
the historical data and our new observations. All available light curves
display total eclipses at secondary minima and inverse O'Connell effects with
Max I fainter than Max II, which are satisfactorily modeled by adding the
slightly time-varying hot spot on the primary star. A total of 87 times of
minimum light spanning over about 74 yrs, including our 22 timing measurements,
were used for ephemeris computations. Detailed analysis of the O-C diagram
showed that the orbital period has changed in combinations with an upward
parabola and a sinusoidal variation. The continuous period increase with a rate
of +5.65 \times 10^-7 d yr^-1 is consistent with that calculated from the
Wilson-Devinney synthesis code. It can be interpreted as a mass transfer from
the secondary to the primary star at a rate of 2.74 \times 10^-7 M\odot yr^-1,
which is one of the largest rates for contact systems. The most likely
explanation of the sinusoidal variation with a period of 30.2 yrs and a
semi-amplitude of 0.0062 d is a light-traveltime effect due to the existence of
a circumbinary object. We suggest that BX Dra is probably a triple system,
consisting of a primary star with a spectral type of F0, its secondary
component of spectral type F1-2, and an unseen circumbinary object with a
minimum mass of M3 = 0.23 M\odot.Comment: 24 pages, including 5 figures and 9 tables, accepted for publication
in PAS
A New SX Phe Star in the Globular Cluster M15
A new SX Phe star (labelled SXP1) found from CCD photometry is the first
to be discovered in the globular cluster M15. It is a blue straggler and is
located 102\arcsec.8 north and 285\arcsec.6 west of the center of M15
\citep{har96}. Mean magnitudes of SXP1 are = 18$\fm$671 and
= 18\fm445. The amplitude of variability of SXP1 is measured to be . From multiple-frequency analysis based on the Fourier
decomposition method, we detect two very closely separated pulsating
frequencies: the primary frequency at c/d for both - and
-bands, and the secondary frequency at c/d for the -band and
24.343 c/d for the -band. This star is the second among known SX Phe stars
found to pulsate with very closely separated frequencies ().
These frequencies may be explained by excitation of nonradial modes; however,
we have an incomplete understanding of this phenomenon in the case of SX Phe
stars with relatively high amplitudes. The metallicity-period and the
variability amplitude-period relations for SXP1 in M15 are found to be
consistent with those for SX Phe stars in other globular clusters.Comment: 15 pages with 6 figures, accepted by the Astronomical Journal
(scheduled May 2001
Silent Microbleeds and Hemorrhagic Conversion of an Embolic Infarction
We report a patient with multiple simultaneous embolic infarctions with localized hemorrhagic conversion. A 75-year-old male patient had several silent microbleeds (SMBs) exclusively in the cerebral cortex, and underwent angioplasty and stenting for bilateral carotid stenosis. He subsequently experienced embolic infarctions in the cortex and the striatum: the cortical infarction, where an SMB had been present, showed hemorrhagic conversion, whereas the striatal infarction did not. This case suggests that SMBs are indicators of an underlying hemorrhage-prone state
REMOTE SENSING OF WAVE DIRECTIONALITY BY TWO-DIMENSIONAL DIRECTIONAL WAVELETS : PART 2. APPLICATIONS TO THE NUMERICAL AND FIELD DATA
This paper presents the results of a study investigating methods of interpretation of wave directionality based on wavelet transform. In part 1 of this paper, the tools to be used in detection of wave directionality, i. e., the Morlet and Cauchy wavelets, were described. This paper presents the application results of the directional wavelet to numerically generated images and video images taken in laboratory wave flume, river, and sea. The results showed that directional wavelet transform can be an efficient tool in detecting wave directionality with extremely low effort and cost when it is compared to traditional practices in use
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