10,848 research outputs found
A Third Exoplanetary System with Misaligned Orbital and Stellar Spin Axes
We present evidence that the WASP-14 exoplanetary system has misaligned
orbital and stellar-rotational axes, with an angle lambda = 33.1 +/- 7.4 deg
between their sky projections. The evidence is based on spectroscopic
observations of the Rossiter-McLaughlin effect as well as new photometric
observations. WASP-14 is now the third system known to have a significant
spin-orbit misalignment, and all three systems have "super-Jupiter" planets
(M_P > 3 Mjup) and eccentric orbits. This finding suggests that the migration
and subsequent orbital evolution of massive, eccentric exoplanets is somehow
different from that of less massive close-in Jupiters, the majority of which
have well-aligned orbits.Comment: 8 pages, 5 figures, 3 tables, PASP accepte
HAT-P-7: A Retrograde or Polar Orbit, and a Third Body
We show that the exoplanet HAT-P-7b has an extremely tilted orbit, with a
true angle of at least 86 degrees with respect to its parent star's equatorial
plane, and a strong possibility of retrograde motion. We also report evidence
for an additional planet or companion star. The evidence for the unparalleled
orbit and the third body is based on precise observations of the star's
apparent radial velocity. The anomalous radial velocity due to rotation (the
Rossiter-McLaughlin effect) was found to be a blueshift during the first half
of the transit and a redshift during the second half, an inversion of the usual
pattern, implying that the angle between the sky-projected orbital and stellar
angular momentum vectors is 182.5 +/- 9.4 degreees. The third body is
implicated by excess radial-velocity variation of the host star over 2 yr. Some
possible explanations for the tilted orbit are a close encounter with another
planet, the Kozai effect, and resonant capture by an inward-migrating outer
planet.Comment: ApJ Letters, in press [7 pages
The power spectra of CMB and density fluctuations seeded by local cosmic strings
We compute the power spectra in the cosmic microwave background and cold dark
matter (CDM) fluctuations seeded by strings, using the largest string
simulations performed so far to evaluate the two-point functions of their
stress energy tensor. We find that local strings differ from global defects in
that the scalar components of the stress-energy tensor dominate over vector and
tensor components. This result has far reaching consequences. We find that
cosmic strings exhibit a single Doppler peak of acceptable height at high
. They also seem to have a less severe bias problem than global defects,
although the CDM power spectrum in the ``standard'' cosmology (flat geometry,
zero cosmological constant, 5% baryonic component) is the wrong shape to fit
large scale structure data
Magnetic Susceptibility for
We examine experimental magnetic susceptibility for
CaVO by fitting with fitting function .
The function is a power series of 1/T and the lowest order
term is fixed as , where is the Curie constant as determined by the
experimental -value (g=1.96). Fitting parameters are , and
expansion coefficients except for the first one in .
We determine and as 0.73 and 0 for an
experimental sample. We interpret as the volume fraction of
CaVO in the sample and as the susceptibility for the
pure CaVO. The result of means that the sample includes
nonmagnetic components. This interpretation consists with the result of a
perturbation theory and a neutron scattering experiment.Comment: 4pages, 4figure
A low stellar obliquity for WASP-47, a compact multiplanet system with a hot Jupiter and an ultra-short period planet
We have detected the Rossiter-Mclaughlin effect during a transit of WASP-47b,
the only known hot Jupiter with close planetary companions. By combining our
spectroscopic observations with Kepler photometry, we show that the projected
stellar obliquity is . We can firmly exclude a
retrograde orbit for WASP-47b, and rule out strongly misaligned prograde
orbits. Low obliquities have also been found for most of the other compact
multiplanet systems that have been investigated. The Kepler-56 system, with two
close-in gas giants transiting their subgiant host star with an obliquity of at
least 45, remains the only clear counterexample.Comment: 5 pages, 2 figures, Accepted for publication on ApJL, comments
welcom
Constraints on the Obliquities of Kepler Planet-Hosting Stars
Stars with hot Jupiters have obliquities ranging from 0-180 degrees, but
relatively little is known about the obliquities of stars with smaller planets.
Using data from the California-Kepler Survey, we investigate the obliquities of
stars with planets spanning a wide range of sizes, most of which are smaller
than Neptune. First, we identify 156 planet hosts for which measurements of the
projected rotation velocity (vsini) and rotation period are both available. By
combining estimates of v and vsini, we find nearly all the stars to be
compatible with high inclination, and hence, low obliquity (less than about 20
degrees). Second, we focus on a sample of 159 hot stars (> 6000K) for which
vsini is available but not necessarily the rotation period. We find 6 stars for
which vsini is anomalously low, an indicator of high obliquity. Half of these
have hot Jupiters, even though only 3% of the stars that were searched have hot
Jupiters. We also compare the vsini distribution of the hot stars with planets
to that of 83 control stars selected without prior knowledge of planets. The
mean vsini of the control stars is lower than that of the planet hosts by a
factor of approximately pi/4, as one would expect if the planet hosts have low
obliquities. All these findings suggest that the Kepler planet-hosting stars
generally have low obliquities, with the exception of hot stars with hot
Jupiters.Comment: AJ, in pres
Single cell mechanics: stress stiffening and kinematic hardening
Cell mechanical properties are fundamental to the organism but remain poorly
understood. We report a comprehensive phenomenological framework for the
nonlinear rheology of single fibroblast cells: a superposition of elastic
stiffening and viscoplastic kinematic hardening. Our results show, that in
spite of cell complexity its mechanical properties can be cast into simple,
well-defined rules, which provide mechanical cell strength and robustness via
control of crosslink slippage.Comment: 4 pages, 6 figure
Effect of Quantum Fluctuations on Magnetic Ordering in CaVO
We present a theoretical model for CaVO: the -depleted square
spin- Heisenberg model which includes both the nearest-neighbor coupling
() and the next-nearest-neighbor coupling (), where and are
antiferromagnetic. Recent experiments of the neutron diffraction by Harashina
et.al. report the magnetic ordering at low temperatures, which may be called as
a stripe phase. It is shown that the observed spin structure is not stable in
the classical theory. By employing the modified spin wave theory, we show that
the stripe phase is stabilized by the quantum fluctuations for .
In CaVO, the coupling constants are estimated as by
comparing the theoretical and experimental results.Comment: submitted to J. Phys. Soc. Jp
Identification of Neutral B Mesons Using Correlated Hadrons
The identification of the flavor of a neutral meson can make use of
hadrons produced nearby in phase space. Examples include the decay of
``'' resonances or the production of hadrons as a result of the
fragmentation process. Some aspects of this method are discussed, including
time-dependent effects in neutral decays to flavor states, to eigenstates
of CP and to other states, and the effects of possible coherence between
and in the initial state. We study the behavior of the leading
hadrons in -quark jets and the expected properties of resonances.
These are extrapolated from the corresponding resonances, of whose
properties we suggest further studies.Comment: To be submitted to Phys. Rev. D. 26 pages, LaTeX, figures not
included (available upon request). Technion-PH-93-32 / EFI 93-4
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