765 research outputs found
Prediction of transits of solar system objects in Kepler/K2 images: An extension of the Virtual Observatory service SkyBoT
All the fields of the extended space mission Kepler/K2 are located within the
ecliptic. Many solar system objects thus cross the K2 stellar masks on a
regular basis. We aim at providing to the entire community a simple tool to
search and identify solar system objects serendipitously observed by Kepler.
The SkyBoT service hosted at IMCCE provides a Virtual Observatory (VO)
compliant cone-search that lists all solar system objects present within a
field of view at a given epoch. To generate such a list in a timely manner,
ephemerides are pre-computed, updated weekly, and stored in a relational
database to ensure a fast access. The SkyBoT Web service can now be used with
Kepler. Solar system objects within a small (few arcminutes) field of view are
identified and listed in less than 10 sec. Generating object data for the
entire K2 field of view (14{\deg}) takes about a minute. This extension of the
SkyBot service opens new possibilities with respect to mining K2 data for solar
system science, as well as removing solar system objects from stellar
photometric time-series
Dynamics of sedimenting active Brownian particles
We investigate the stochastic dynamics of one sedimenting active Brownian particle in three
dimensions under the influence of gravity and passive fluctuations in the translational and rotational
motion. We present an analytical solution of the Fokker-Planck equation for the stochastic process which
allows us to describe the dynamics of one active Brownian particle in three dimensions. We address the
time evolution of the density, the polarization, and the steady-state solution. We also perform Brownian
dynamics simulations and study the effect of the activity of the particles on their collective motion. These
results qualitatively agree with our model. Finally, we compare our results with experiments (J. Palacci et
al., Phys. Rev. Lett. 105, 088304 (2010)) and find very good agreement
Extreme AO Observations of Two Triple Asteroid Systems with SPHERE
We present the discovery of a new satellite of asteroid (130) Elektra -
S/2014 (130) 1 - in differential imaging and in integral field spectroscopy
data over multiple epochs obtained with SPHERE/VLT. This new (second) moonlet
of Elektra is about 2 km across, on an eccentric orbit and about 500 km away
from the primary. For a comparative study, we also observed another triple
asteroid system (93) Minerva. For both systems, component-resolved reflectance
spectra of the satellites and primary were obtained simultaneously. No
significant spectral difference was observed between the satellites and the
primary for either triple system. We find that the moonlets in both systems are
more likely to have been created by sub-disruptive impacts as opposed to having
been captured.Comment: 8 pages, 4 figures, 1 table, accepted to be published in the
Astrophysical Journal Letter
Determination of binary asteroid orbits with a genetic-based algorithm
Reproduced with permission. Copyright ESO. The original publication is available at www.aanda.org.International audienceAims: Over the past decade, discoveries of multiple and binary asteroid systems have played a significant role in our general understanding of small solar system bodies. Direct observations of satellites of asteroids are rare and difficult since they require the use of already over-subscribed facilities such as adaptive optics (AO) on large 8-10 m class telescopes and the Hubble Space Telescope (HST). The scarcity of data and the long temporal baseline of observations (up to 10 years) significantly complicate the determination of the mutual orbits of these systems. Methods: We implemented a new approach for determining the mutual orbits of directly-imaged multiple asteroids using a genetic-based algorithm. This approach was applied to several known binary asteroid systems (22 Kalliope, 3749 Balam, and 50 000 Quaoar) observed with AO systems and HST. This statistical method is fast enough to permit the search for an orbital solution across a large parameter space and without a priori information about the mutual orbit. Results: From 10 years of observation, we derived an orbital solution for Linus, companion of (22) Kalliope, with an accuracy close to the astrometric limit provided by the AO observations, assuming a purely Keplerian orbit. A search for non-Keplerian orbit confirmed that a J2 ~ 0 is the best-fitting solution. We show that the precession of the nodes could be detected without ambiguity, implying that Kalliope's primary may have an inhomogeneous internal structure. HST astrometric observations of Weywot, companion of the trans-Neptunian object (50 000) Quaoar, were used to derive its mass and its bulk density, which appears to be higher than the density of other TNOs. Finally, we derived a bundle of orbital solutions for (3749) Balam, with equally good fits, from the limited set of astrometric positions. They provide a realistic density between 1.3 and 3.7 g/cm3 for this S-type asteroid
Near-infrared spatially resolved spectroscopy of (136108) Haumea's multiple system
The transneptunian region of the solar system is populated by a wide variety
of icy bodies showing great diversity. The dwarf planet (136108) Haumea is
among the largest TNOs and displays a highly elongated shape and hosts two
moons, covered with crystalline water ice like Hamuea. Haumea is also the
largest member of the sole TNO family known to date. A catastrophic collision
is likely responsible for its unique characteristics. We report here on the
analysis of a new set of observations of Haumea obtained with SINFONI at the
ESO VLT. Combined with previous data, and using light-curve measurements in the
optical and far infrared, we carry out a rotationally resolved spectroscopic
study of the surface of Haumea. We describe the physical characteristics of the
crystalline water ice present on the surface of Haumea for both regions, in and
out of the Dark Red Spot (DRS), and analyze the differences obtained for each
individual spectrum. The presence of crystalline water ice is confirmed over
more than half of the surface of Haumea. Our measurements of the average
spectral slope confirm the redder characteristic of the spot region. Detailed
analysis of the crystalline water-ice absorption bands do not show significant
differences between the DRS and the remaining part of the surface. We also
present the results of applying Hapke modeling to our data set. The best
spectral fit is obtained with a mixture of crystalline water ice (grain sizes
smaller than 60 micron) with a few percent of amorphous carbon. Improvements to
the fit are obtained by adding ~10% of amorphous water ice. Additionally, we
used the IFU-reconstructed images to measure the relative astrometric position
of the largest satellite Hi`iaka and determine its orbital elements. An orbital
solution was computed with our genetic-based algorithm GENOID and our results
are in full agreement with recent results.Comment: Accepted for publication in A&
Efetividade do programa FIFA 11+ na prevenção das lesões musculares e ligamentares do membro inferior em jogadores de futebol: revisão bibliográfica
Projeto de Graduação apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Licenciado em FisioterapiaObjetivo: Averiguar a efetividade do programa FIFA 11+ na prevenção das lesões musculares
e ligamentares do membro inferior em jogadores de futebol.
Metodologia: As pesquisas foram feitas nas bases de dados PubMed, PEDro, ScienceDirect,
SciELO e Web of Science e MEDLINE via Web of Knowledge para identificar os estudos
randomizados controlados que avaliam a efetividade do programa da FIFA 11+ na prevenção
de lesões musculares e ligamentares do membro inferior em jogadores de futebol.
Resultados: Nesta revisĂŁo foram incluĂdos 5 artigos envolvendo 5623 pacientes, com
classificação da qualidade metodológica média de 5 na escala de Physiotherapy Evidence
Database (PEDro).
Conclusão: O programa de prevenção das lesões FIFA 11+ não pôde garantir de forma
significativa efetividade na prevenção especifica das lesões musculares e noutras lesões
ligamentares do membro inferior em jogadores de futebol, nem o efeito preventivo em
jogadores veteranos. No entanto, o programa apresentou efetividade na prevenção das lesões
do ligamento cruzado anterior e nas lesões totais do membro inferior nos jogadores de futebol.Objective: To investigate the effectiveness of the FIFA 11+ programme in preventing muscular
and ligament injuries of the lower limb in football players.
Methodology: Research was conducted on PubMed, PEDro, ScienceDirect, SciELO and Web
of Science and MEDLINE via the Web of Knowledge to identify randomised controlled trials
that assess the effectiveness of the FIFA 11+ programme in preventing lower limb muscle and
ligament injuries in football players.
Results: This review included 5 articles involving 5623 patients, with an average
methodological quality score of 5 on the Physiotherapy Evidence Database (PEDro) scale.
Conclusion: The FIFA 11+ injury prevention programme has not been able to guarantee any
significant effectiveness in preventing specific muscle and other ligament injuries of the lower
limb in football players, nor the preventive effect on veteran players. However, the programme
has been effective in preventing anterior cruciate ligament injuries and total lower limb injuries
in football players.N/
GRB 110205A: Anatomy of a long gamma-ray burst
The Swift burst GRB 110205A was a very bright burst visible in the Northern
hemisphere. GRB 110205A was intrinsically long and very energetic and it
occurred in a low-density interstellar medium environment, leading to delayed
afterglow emission and a clear temporal separation of the main emitting
components: prompt emission, reverse shock, and forward shock. Our observations
show several remarkable features of GRB 110205A : the detection of prompt
optical emission strongly correlated with the BAT light curve, with no temporal
lag between the two ; the absence of correlation of the X-ray emission compared
to the optical and high energy gamma-ray ones during the prompt phase ; and a
large optical re-brightening after the end of the prompt phase, that we
interpret as a signature of the reverse shock. Beyond the pedagogical value
offered by the excellent multi-wavelength coverage of a GRB with temporally
separated radiating components, we discuss several questions raised by our
observations: the nature of the prompt optical emission and the spectral
evolution of the prompt emission at high-energies (from 0.5 keV to 150 keV) ;
the origin of an X-ray flare at the beginning of the forward shock; and the
modeling of the afterglow, including the reverse shock, in the framework of the
classical fireball model.Comment: 21 pages, 5 figure (all in colors), accepted for publication in Ap
Physical and dynamical properties of the main belt triple asteroid (87) Sylvia
We present the analysis of high angular resolution observations of the triple
Asteroid (87) Sylvia collected with three 8-10 m class telescopes (Keck, VLT,
Gemini North) and the Hubble Space Telescope. The moons' mutual orbits were
derived individually using a purely Keplerian model. We computed the position
of Romulus, the outer moon of the system, at the epoch of a recent stellar
occultation which was successfully observed at less than 15 km from our
predicted position, within the uncertainty of our model. The occultation data
revealed that the Moon, with a surface-area equivalent diameter
Ds=23.10.7km, is strongly elongated (axes ratio of
2.70.32.70.3), significantly more than single asteroids of similar
size in the main-belt. We concluded that its shape is probably affected by the
tides from the primary. A new shape model of the primary was calculated
combining adaptive-optics observations with this occultation and 40 archived
light-curves recorded since 1978. The difference between the
J2=0.024-0.009+0.016 derived from the 3-D shape model assuming an homogeneous
distribution of mass for the volume equivalent diameter Dv=27310km primary
and the null J2 implied by the Keplerian orbits suggests a non-homogeneous mass
distribution in the asteroid's interior
The Puzzling Mutual Orbit of the Binary Trojan Asteroid (624) Hektor
Asteroids with satellites are natural laboratories to constrain the formation
and evolution of our solar system. The binary Trojan asteroid (624) Hektor is
the only known Trojan asteroid to possess a small satellite. Based on W.M. Keck
adaptive optics observations, we found a unique and stable orbital solution,
which is uncommon in comparison to the orbits of other large multiple asteroid
systems studied so far. From lightcurve observations recorded since 1957, we
showed that because the large Req=125-km primary may be made of two joint
lobes, the moon could be ejecta of the low-velocity encounter, which formed the
system. The inferred density of Hektor's system is comparable to the L5 Trojan
doublet (617) Patroclus but due to their difference in physical properties and
in reflectance spectra, both captured Trojan asteroids could have a different
composition and origin.Comment: 13 pages, 3 figures, 2 table
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