1,522 research outputs found
A pair of planets around HD 202206 or a circumbinary planet?
Long-term precise Doppler measurements with the CORALIE spectrograph reveal
the presence of a second planet orbiting the solar-type star HD202206. The
radial-velocity combined fit yields companion masses of m_2\sini = 17.4 M_Jup
and 2.44 M_Jup, semi-major axes of a = 0.83 AU and 2.55 AU, and eccentricities
of e = 0.43 and 0.27, respectively. A dynamical analysis of the system further
shows a 5/1 mean motion resonance between the two planets. This system is of
particular interest since the inner planet is within the brown-dwarf limits
while the outer one is much less massive. Therefore, either the inner planet
formed simultaneously in the protoplanetary disk as a superplanet, or the outer
Jupiter-like planet formed in a circumbinary disk. We believe this singular
planetary system will provide important constraints on planetary formation and
migration scenarios.Comment: 9 pages, 14 figures, accepted in A&A, 12-May-200
Dynamical stability analysis of the HD202206 system and constraints to the planetary orbits
Long-term precise Doppler measurements with the CORALIE spectrograph revealed
the presence of two massive companions to the solar-type star HD202206.
Although the three-body fit of the system is unstable, it was shown that a 5:1
mean motion resonance exists close to the best fit, where the system is stable.
We present here an extensive dynamical study of the HD202206 system aiming at
constraining the inclinations of the two known companions, from which we derive
possible ranges of value for the companion masses.
We study the long term stability of the system in a small neighborhood of the
best fit using Laskar's frequency map analysis. We also introduce a numerical
method based on frequency analysis to determine the center of libration mode
inside a mean motion resonance.
We find that acceptable coplanar configurations are limited to inclinations
to the line of sight between 30 and 90 degrees. This limits the masses of both
companions to roughly twice the minimum. Non coplanar configurations are
possible for a wide range of mutual inclinations from 0 to 90 degrees, although
configurations seem to be favored. We also confirm the
5:1 mean motion resonance to be most likely. In the coplanar edge-on case, we
provide a very good stable solution in the resonance, whose does not
differ significantly from the best fit. Using our method to determine the
center of libration, we further refine this solution to obtain an orbit with a
very low amplitude of libration, as we expect dissipative effects to have
dampened the libration.Comment: 14 pages, 18 figure
Interesting dynamics at high mutual inclination in the framework of the Kozai problem with an eccentric perturber
We study the dynamics of the 3-D three-body problem of a small body moving
under the attractions of a star and a giant planet which orbits the star on a
much wider and elliptic orbit. In particular, we focus on the influence of an
eccentric orbit of the outer perturber on the dynamics of a small highly
inclined inner body. Our analytical study of the secular perturbations relies
on the classical octupole hamiltonian expansion (third-order theory in the
ratio of the semi-major axes), as third-order terms are needed to consider the
secular variations of the outer perturber and potential secular resonances
between the arguments of the pericenter and/or longitudes of the node of both
bodies. Short-period averaging and node reduction (Laplace plane) reduce the
problem to two degrees of freedom. The four-dimensional dynamics is analyzed
through representative planes which identify the main equilibria of the
problem. As in the circular problem (i.e. perturber on a circular orbit), the
"Kozai-bifurcated" equilibria play a major role in the dynamics of an inner
body on quasi-circular orbit: its eccentricity variations are very limited for
mutual inclination between the orbital planes smaller than ~40^{\deg}, while
they become large and chaotic for higher mutual inclination. Particular
attention is also given to a region around 35^{\deg} of mutual inclination,
detected numerically by Funk et al. (2011) and consisting of long-time stable
and particularly low eccentric orbits of the small body. Using a 12th-order
Hamiltonian expansion in eccentricities and inclinations, in particular its
action-angle formulation obtained by Lie transforms in Libert & Henrard (2008),
we show that this region presents an equality of two fundamental frequencies
and can be regarded as a secular resonance. Our results also apply to binary
star systems where a planet is revolving around one of the two stars.Comment: 12 pages, 9 figures, accepted for publication in MNRA
Detecting chaos in particle accelerators through the frequency map analysis method
The motion of beams in particle accelerators is dominated by a plethora of
non-linear effects which can enhance chaotic motion and limit their
performance. The application of advanced non-linear dynamics methods for
detecting and correcting these effects and thereby increasing the region of
beam stability plays an essential role during the accelerator design phase but
also their operation. After describing the nature of non-linear effects and
their impact on performance parameters of different particle accelerator
categories, the theory of non-linear particle motion is outlined. The recent
developments on the methods employed for the analysis of chaotic beam motion
are detailed. In particular, the ability of the frequency map analysis method
to detect chaotic motion and guide the correction of non-linear effects is
demonstrated in particle tracking simulations but also experimental data.Comment: Submitted for publication in Chaos, Focus Issue: Chaos Detection
Methods and Predictabilit
On the Dynamical Stability of the Solar System
A long-term numerical integration of the classical Newtonian approximation to
the planetary orbital motions of the full Solar System (sun + 8 planets),
spanning 20 Gyr, was performed. The results showed no severe instability
arising over this time interval. Subsequently, utilizing a bifurcation method
described by Jacques Laskar, two numerical experiments were performed with the
goal of determining dynamically allowed evolutions for the Solar System in
which the planetary orbits become unstable. The experiments yielded one
evolution in which Mercury falls onto the Sun at ~1.261Gyr from now, and
another in which Mercury and Venus collide in ~862Myr. In the latter solution,
as a result of Mercury's unstable behavior, Mars was ejected from the Solar
System at ~822Myr. We have performed a number of numerical tests that confirm
these results, and indicate that they are not numerical artifacts. Using
synthetic secular perturbation theory, we find that Mercury is destabilized via
an entrance into a linear secular resonance with Jupiter in which their
corresponding eigenfrequencies experience extended periods of commensurability.
The effects of general relativity on the dynamical stability are discussed. An
application of the bifurcation method to the outer Solar System (Jupiter,
Saturn, Uranus, and Neptune) showed no sign of instability during the course of
24Gyr of integrations, in keeping with an expected Uranian dynamical lifetime
of 10^(18) years.Comment: 37 pages, 18 figures, accepted for publication in the Astrophysical
Journa
An Overview of the 13:8 Mean Motion Resonance between Venus and Earth
It is known since the seminal study of Laskar (1989) that the inner planetary
system is chaotic with respect to its orbits and even escapes are not
impossible, although in time scales of billions of years. The aim of this
investigation is to locate the orbits of Venus and Earth in phase space,
respectively to see how close their orbits are to chaotic motion which would
lead to unstable orbits for the inner planets on much shorter time scales.
Therefore we did numerical experiments in different dynamical models with
different initial conditions -- on one hand the couple Venus-Earth was set
close to different mean motion resonances (MMR), and on the other hand Venus'
orbital eccentricity (or inclination) was set to values as large as e = 0.36 (i
= 40deg). The couple Venus-Earth is almost exactly in the 13:8 mean motion
resonance. The stronger acting 8:5 MMR inside, and the 5:3 MMR outside the 13:8
resonance are within a small shift in the Earth's semimajor axis (only 1.5
percent). Especially Mercury is strongly affected by relatively small changes
in eccentricity and/or inclination of Venus in these resonances. Even escapes
for the innermost planet are possible which may happen quite rapidly.Comment: 14 pages, 11 figures, submitted to CMD
A Review on Application of Biosensors for Cancer Detection
Cancer is a deadly disease that has devastated many lives over the years. Cancer, when detected in the early stage, can be cured through proper treatment, increasing the life expectancy of the patient. Thus, it is very important to detect cancer at the early stage. The current method of cancer detection is biopsy which is a total invasive medical procedure. Owing to the several limitations of the time-consuming procedure of biopsy researchers and scientist all over the globe have turned their attention towards the development of instruments for rapid and non-invasive detection of cancer through detection of clinically recognized cancer biomarkers present in blood and other body fluid of cancer patients. This paper discusses some of the novel biomarkers used for cancer diagnosis along with the potential use of biosensors in early detection of cancer
Local control of Hamiltonian chaos
We review a method of control for Hamiltonian systems which is able to create
smooth invariant tori. This method of control is based on an apt modification
of the perturbation which is small and localized in phase space
Distributed Optical Fiber Sensor and Its Various Applications
The process of sensing can also be done with the help of optical fiber. This method of sensing is becoming very popular. The optical communication, which is the main communication technology, in this case, takes light as the carrier and optical fiber as the communication medium. Distributed Optical Fiber Sensors (DOFS) can be used for continuous measurement at the same time to obtain the spatial distribution of the measured state and time-varying information. This paper describes the background of DOFS technology. Various applications of DOFS are also listed
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