5,184 research outputs found
Systematic Mischaracterization of Exoplanetary System Dynamical Histories from a Model Degeneracy near Mean-motion Resonance
There is a degeneracy in the radial velocity exoplanet signal between a single planet on an eccentric orbit and a two-planet system with a period ratio of 2:1. This degeneracy could lead to misunderstandings of the dynamical histories of planetary systems as well as measurements of planetary abundances if the correct architecture is not established. We constrain the rate of mischaracterization by analysing a sample of 60 non-transiting, radial velocity systems orbiting main-sequence stars from the NASA Exoplanet Archive (NASA Archive) using a new Bayesian model comparison pipeline. We find that 15 systems (25 per cent of our sample) show compelling evidence for the two-planet case with a confidence level of 95 per cent
L'idéologie marchande au service de la biodiversité ?
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Long-Period Giant Companions to Three Compact, Multiplanet Systems
Understanding the relationship between long-period giant planets and multiple smaller short-period planets is critical for formulating a complete picture of planet formation. This work characterizes three such systems. We present Kepler-65, a system with an eccentric (e = 0.28 ± 0.07) giant planet companion discovered via radial velocities (RVs) exterior to a compact, multiply transiting system of sub-Neptune planets. We also use precision RVs to improve mass and radius constraints on two other systems with similar architectures, Kepler-25 and Kepler-68. In Kepler-68 we propose a second exterior giant planet candidate. Finally, we consider the implications of these systems for planet formation models, particularly that the moderate eccentricity in Kepler-65\u27s exterior giant planet did not disrupt its inner system
Collective modes of CP(3) Skyrmion crystals in quantum Hall ferromagnets
The two-dimensional electron gas in a bilayer quantum Hall system can sustain
an interlayer coherence at filling factor nu=1 even in the absence of tunneling
between the layers. This system has low-energy charged excitations which may
carry textures in real spin or pseudospin. Away from filling factor nu =1 a
finite density of these is present in the ground state of the 2DEG and forms a
crystal. Depending on the relative size of the various energy scales, such as
tunneling (Delta_SAS), Zeeman coupling (Delta_Z) or electrical bias (Delta_b),
these textured crystal states can involve spin, pseudospin, or both
intertwined. In this article, we present a comprehensive numerical study of the
collective excitations of these textured crystals using the GRPA. For the pure
spin case, at finite Zeeman coupling the state is a Skyrmion crystal with a
gapless phonon mode, and a separate Goldstone mode that arises from a broken
U(1) symmetry. At zero Zeeman coupling, we demonstrate that the constituent
Skyrmions break up, and the resulting state is a meron crystal with 4 gapless
modes. In contrast, a pure pseudospin Skyrme crystal at finite tunneling has
only the phonon mode. For Delta_SAS=0, the state evolves into a meron crystal
and supports an extra gapless U(1) mode in addition to the phonon. For a CP(3)
Skyrmion crystal, we find a U(1) gapless mode in the presence of the
symmetry-breaking fields. In addition, a second mode with a very small gap is
present in the spectrum.Comment: 16 pages and 12 eps figure
Abcès du chat à Mycobacterium chelonei
Un cas à abcès cutanés multiples dû à Mycobacterium chelonei est décrit chez le chat. L’origine éventuelle de ces abcès est discutée .A case of multiple cutaneous abcessus du to Mycobacterium chelonei is discribed in the cat. The possible origin is discussed
An Unobscured type II quasar candidate: SDSS J012032.19-005501.9
We report the finding of an unobscured type II Active Galactic Nuclei (AGN)
candidate, SDSS J012032.19-005501.9 at a relatively high redshift of
0.601,which shows a number of unusual properties. It varies significantly on
timescales of years as typical type I AGNs and marginally on timescales of
weeks. The color-magnitude relation and the structure function are also
consistent with that of type I AGNs, which imply that its variability likely
originates from the black hole accretion system .However, no broad emission
line is detected in the SDSS spectrum, and the upper limit of the equivalent
width of the H broad emission line is much less than that of type I
AGNs. These properties suggest that SDSS J012032.19-005501.9 may be an
unobscured quasar without broad emission lines intrinsically, namely an
unobscured type II AGN or "true" type II AGN. Furthermore, its continuum
luminosity is at least one order of magnitude fainter than the average value of
thepast century expected from the [OIII] emission line. It indicates that SDSS
J012032.19-005501.9 may be switching off. Additional possible scenarios to
explain this intriguing source are also discussed. Future deep observations at
multi-wavelengths are needed to reveal the nature of this peculiar and
intriguing AGN.Comment: 8 pages, 7 figures, 1 table, accepted for publication in The
Astronomical Journa
Self-diffusion of adatoms, dimers, and vacancies on Cu(100)
We use ab initio static relaxation methods and semi-empirical
molecular-dynamics simulations to investigate the energetics and dynamics of
the diffusion of adatoms, dimers, and vacancies on Cu(100). It is found that
the dynamical energy barriers for diffusion are well approximated by the
static, 0 K barriers and that prefactors do not depend sensitively on the
species undergoing diffusion. The ab initio barriers are observed to be
significantly lower when calculated within the generalized-gradient
approximation (GGA) rather than in the local-density approximation (LDA). Our
calculations predict that surface diffusion should proceed primarily via the
diffusion of vacancies. Adatoms are found to migrate most easily via a jump
mechanism. This is the case, also, of dimers, even though the corresponding
barrier is slightly larger than it is for adatoms. We observe, further, that
dimers diffuse more readily than they can dissociate. Our results are discussed
in the context of recent submonolayer growth experiments of Cu(100).Comment: Submitted to the Physical Review B; 15 pages including postscript
figures; see also http://www.centrcn.umontreal.ca/~lewi
Further Evaluation of the Associations Between Psychopathic Traits and Symptoms of PTSD and Depression in a Nonclinical Sample
Examining psychopathic traits at the factor or facet level has revealed that various aspects of psychopathy may be differentially related, even in opposing directions, to important outcomes (e.g., intelligence, emotion regulation). Empirical work on relations between psychopathy and internalizing disorders, such as posttraumatic stress disorder (PTSD) and depression, has provided evidence for a positive association with antisocial traits. However, findings for the affective domain have been more equivocal. The current study (N = 732) sought to replicate past findings of the positive association of antisocial psychopathic traits with higher levels of PTSD and depressive symptoms, and to further explore associations between affective traits of psychopathy and these disorders using two measures of psychopathy. Results confirmed prior findings of a positive correlation between antisocial features and self-reported PTSD/Depression symptom severity, but they did not provide evidence for any association with affective traits. Future research using longitudinal designs is needed to begin establishing temporal ordering of the psychopathy–internalizing relationship
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