7,239 research outputs found
The Statistical Analyses of the White-Light Flares: Two Main Results About Flare Behaviours
We present two main results, based on the models and the statistical analyses
of 1672 U-band flares. We also discuss the behaviours of the white-light
flares. In addition, the parameters of the flares detected from two years of
observations on CR Dra are presented. By comparing with the flare parameters
obtained from other UV Ceti type stars, we examine the behaviour of optical
flare processes along the spectral types. Moreover, we aimed, using large
white-light flare data,to analyse the flare time-scales in respect to some
results obtained from the X-ray observations. Using the SPSS V17.0 and the
GraphPad Prism V5.02 software, the flares detected from CR Dra were modelled
with the OPEA function and analysed with t-Test method to compare similar flare
events in other stars. In addition, using some regression calculations in order
to derive the best histograms, the time-scales of the white-light flares were
analysed. Firstly, CR Dra flares have revealed that the white-light flares
behave in a similar way as their counterparts observed in X-rays. As seen in
X-ray observations, the electron density seems to be a dominant parameter in
white-light flare process, too. Secondly, the distributions of the flare
time-scales demonstrate that the number of observed flares gets a maximum value
in some particular ratios, which are 0.5 or its multiples, and especially
positive integers. The thermal processes might be dominant for these
white-light flares, while non-thermal processes might be dominant in the
others. To reach better results for the behaviour of the white-light flare
process along the spectral types, much more stars in a wide spectral range,
from the spectral type dK5e to dM6e, must be observed in the white-light flare
patrols.Comment: 17 pages, 7 figures, 5 tabl
A Gamma Doradus Candidate In Eclipsing Binary BD And?
The BVR photometric light curves of the eclipsing binary BD And were obtained
in 2008 and 2009. We estimated the mass ratio of the system as 0.97 and the
photometric solutions were derived. The results show that BD And is a detached
binary system, whose components have a little temperature difference of about
40 K. By analyzing photometric available light minimum times, we also derived
an update ephemeris and found for the first time a possible periodic
oscillation with an amplitude of 0.011 days and a period of 9.6 years. The
results indicate that the periodic oscillation could be caused by a third
component physically attached to the eclipsing binary. After removing the light
variations due to the eclipses and proximity effects, the light-curve
distortions are further explained by the pulsation of the primary component
with a dominant period of 1 day. In accordance with the position of the primary
component on the Hertzsprung-Russell diagram and its pulsation period, the
primary component of BD And could be an excellent gamma Doradus candidate. It
is rarely phenomenon that a component of the eclipsing binary system is a gamma
Doradus variable.Comment: 34 pages, 8 figures. arXiv admin note: text overlap with
arXiv:1112.1916 by other authors without attributio
Uniqueness of solutions to Hamilton-Jacobi equations arising in the Calculus of Variations
We prove the uniqueness of the viscosity solution to the Hamilton-Jacobi
equation associated with a Bolza problem of the Calculus of Variations,
assuming that the Lagrangian is autonomous, continuous, superlinear, and
satisfies the usual convexity hypothesis. Under the same assumptions we prove
also the uniqueness, in a class of lower semicontinuous functions, of a
slightly different notion of solution, where classical derivatives are replaced
only by subdifferentials. These results follow from a new comparison theorem
for lower semicontinuous viscosity supersolutions of the Hamilton-Jacobi
equation, that is proved in the general case of lower semicontinuous
Lagrangians.Comment: 14 page
Rotation Modulations and Distributions of the Flare Occurrence Rates on the Surface of Five UV Ceti Type Stars
In this study, we considered stellar spots, stellar flares, and also the
relation between these two magnetic proccesses that take place on UV Cet stars.
In addition, the hypothesis about slow flares described by Gurzadyan (1986
Ap&SS, 125, 127) was investigated. All of these discussions were based on the
results of three years of observations of UV Cet-type stars: AD Leo, EV Lac,
V1005 Ori, EQ Peg, and V1054 Oph. First of all, the results show that stellar
spot activity occurs on the stellar surface of EV Lac, V1005 Ori, and EQ Peg,
while AD Leo does not show any short-term variability and V1054 Oph does not
exhibit any variability. We report on new ephemerides for EV Lac, V1005 Ori,
and EQ Peg, obtained from time-series analyses. The phases, computed at
intervals of 0.10 phase length, where the mean flare occurence rates to obtain
maximum amplitude; also, the phases of rotational modulation were compared in
order to investigate whether there is any longitudinal relation between stellar
flares and spots. Although the results show that flare events are related with
spotted areas on stellar surfaces during some of the observing seasons, we did
not find any clear correlation among them. Finally, it was tested whether slow
flares are fast flares occurring on the opposite side of the stars according to
the direction of the observers, as mentioned in a hypothesis developed by <A
>Gurzadyan (1986). The flare occurence rates reveal that both slow and fast
flares can occur in any rotational phases. The flare occurence rates of both
fast and slow flares vary in the same way along the longitudes for all program
stars. These results are not expected based on the case mentioned in the
hypothesis.Comment: 24 pages, 15 figures, 6 tabels, 2011PASJ...63..427
Absolute Properties of An Overcontact Binary HH Boo
We obtained multi-colour light curves of HH Boo. We analysed the orbital
period variation of the system. The analysis indicated that there is possible
mass transfer from the second component to the primary or mass loss with
-5.04x10-7 Msun per year. Re-analysing the available radial velocity curve, we
analysed the light curves. The inclination (i) of the system was found to be
69.71(0.16) deg, while the semi-major axis (a) was computed as 2.246(0.064)
Rsun. The mass of the primary component was found to be 0.92(0.08) Msun, while
it was obtained as 0.58(0.06) Msun for the secondary component. The radius of
the primary component was computed as 0.98(0.03) Rsun, while it was computed as
0.80(0.02) Rsun for the secondary component. We demonstrated that HH Boo should
be a member of the A-type subclass of W UMa binaries.Comment: 20 pages, 5 figures, 4 table
Crack phase-field modeling of anisotropic rupture in fibrous soft tissues
The estimation of rupture in fibrous soft tissues has emerged as a central task in medical monitoring and risk assessment of diseases such as aortic dissection and aneurysms. In an attempt to address the challenges we have established a computational framework within the context of crack phase-field modeling and proposed an energy-based anisotropic failure criterion based on the distinction of isotropic and anisotropic material responses. Numerically we compare that criterion with other anisotropic failure criteria, in particular we analyze their capability to describe an admissible failure surface and how a crack can be propagated. A canonical rate-dependent setting of the crack phase-field model is formulated and solved in a weak sense by a standard Galerkin procedure featuring a one-pass operator-splitting algorithm on the temporal side. The anisotropic failure criteria are tested according to their performance on reflecting an admissible initiation, and crack propagation with an emphasis placed upon the aortic dissection
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