37,879 research outputs found
Inflating and Deflating Hot Jupiters: Coupled Tidal and Thermal Evolution of Known Transiting Planets
We examine the radius evolution of close-in giant planets with a planet
evolution model that couples the orbital-tidal and thermal evolution. For 45
transiting systems, we compute a large grid of cooling/contraction paths
forward in time, starting from a large phase space of initial semi-major axes
and eccentricities. Given observational constraints at the current time for a
given planet (semi-major axis, eccentricity, and system age) we find possible
evolutionary paths that match these constraints, and compare the calculated
radii to observations. We find that tidal evolution has two effects. First,
planets start their evolution at larger semi-major axis, allowing them to
contract more efficiently at earlier times. Second, tidal heating can
significantly inflate the radius when the orbit is being circularized, but this
effect on the radius is short-lived thereafter. Often circularization of the
orbit is proceeded by a long period while the semi-major axis slowly decreases.
Some systems with previously unexplained large radii that we can reproduce with
our coupled model are HAT-P-7, HAT-P-9, WASP-10, and XO-4. This increases the
number of planets for which we can match the radius from 24 (of 45) to as many
as 35 for our standard case, but for some of these systems we are required to
be viewing them at a special time around the era of current radius inflation.
This is a concern for the viability of tidal inflation as a general mechanism
to explain most inflated radii. Also, large initial eccentricities would have
to be common. We also investigate the evolution of models that have a floor on
the eccentricity, as may be due to a perturber. In this scenario we match the
extremely large radius of WASP-12b. (Abridged)Comment: 18 pages, 14 figures, 2 tables, Accepted for publication in Ap
The Velocity Field of Quasar Broad Emission Line Gas
In this Letter, the broad emission line (BEL) profiles of superluminal
quasars with apparent jet velocities, , (ultraluminal QSOs, or
ULQSOs hereafter) are studied as a diagnostic of the velocity field of the BEL
emitting gas in quasars. The ULQSOs are useful because they satisfy a very
strict kinematical constraint, their parsec scale jets must be propagating
within of the line of sight. We know the orientation of these
objects with great certainty. The large BEL FWHM, , in ULQSOs tend to indicate that the BEL gas has a larger
component of axial velocity (either random or in a wind) along the jet
direction than previously thought.Comment: To appear in ApJ Letter
Support Vector Machine classification of strong gravitational lenses
The imminent advent of very large-scale optical sky surveys, such as Euclid
and LSST, makes it important to find efficient ways of discovering rare objects
such as strong gravitational lens systems, where a background object is
multiply gravitationally imaged by a foreground mass. As well as finding the
lens systems, it is important to reject false positives due to intrinsic
structure in galaxies, and much work is in progress with machine learning
algorithms such as neural networks in order to achieve both these aims. We
present and discuss a Support Vector Machine (SVM) algorithm which makes use of
a Gabor filterbank in order to provide learning criteria for separation of
lenses and non-lenses, and demonstrate using blind challenges that under
certain circumstances it is a particularly efficient algorithm for rejecting
false positives. We compare the SVM engine with a large-scale human examination
of 100000 simulated lenses in a challenge dataset, and also apply the SVM
method to survey images from the Kilo-Degree Survey.Comment: Accepted by MNRA
A survey of polarization in the JVAS/CLASS flat-spectrum radio source surveys: I. The data and catalogue production
We have used the very large JVAS/CLASS 8.4-GHz surveys of flat-spectrum radio
sources to obtain a large, uniformly observed and calibrated, sample of radio
source polarizations. These are useful for many investigations of the
properties of radio sources and the interstellar medium. We discuss comparisons
with polarization measurements from this survey and from other large-scale
surveys of polarization in flat-spectrum sources.Comment: Accepted by MNRAS. 8 pages, 5 figures. Full version of Table 2
available at http://www.jb.man.ac.uk/~njj/classqu_po
Stable isotope studies on granulites from the high grade terrain of Southern India
Fluid inclusion and petrologic characteristics of South India granulites and their bearing on the sources of metamorphic fluids are discussed. This paper served as a review and an introduction to the next paper by D. Jackson. Jackson presented carbon isotope data from gases extracted from fluid inclusions in South Indian granulites. The uniformly low Delta C-13 values (minus 10 plus or minus 2 per mil) and the greater abundance of CO2 in the incipient charnockites are suggestive of fluid influx from an externally buffered reservoir
Characteristics and carbon stable isotopes of fluids in the Southern Kerala granulites and their bearing on the source of CO2
Carbon dioxide-rich inclusions commonly occur in the banded charnockites and khondalites of southern Kerala as well as in the incipient charnockites formed by desiccation of gneisses along oriented zones. The combined high density fluid inclusion isochores and the range of thermometric estimates from mineral assemblages indicate entrapment pressures in the range of 5.4 to 6.1 Kbar. The CO2 equation of state barometry closely compares with the 5 plus or minus 1 Kbar estimate from mineral phases for the region. The isochores for the high density fluid inclusions in all the three rock types pass through the P-T domain recorded by phase equilibria, implying that carbon dioxide was the dominating ambient fluid species during peak metamorphic conditions. In order to constrain the source of fluids and to evaluate the mechanism of desiccation, researchers undertook detailed investigations of the carbon stable isotope composition of entrapped fluids. Researchers report here the results of preliminary studies in some of the classic localities in southern Kerala namely, Ponmudi, Kottavattom, Manali and Kadakamon
Lifshitz Interaction between Dielectric Bodies of Arbitrary Geometry
A formulation is developed for the calculation of the
electromagnetic--fluctuation forces for dielectric objects of arbitrary
geometry at small separations, as a perturbative expansion in the dielectric
contrast. The resulting Lifshitz energy automatically takes on the form of a
series expansion of the different many-body contributions. The formulation has
the advantage that the divergent contributions can be readily determined and
subtracted off, and thus makes a convenient scheme for realistic numerical
calculations, which could be useful in designing nano-scale mechanical devices
Draft genome sequence of "Candidatus Cronobacter colletis" NCTC 14934T, a new species in the genus Cronobacter
Members of the Cronobacter genus are associated with serious infections in neonates. This is the first report of the draft genome sequence for the newly proposed species Cronobacter colletis
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