279 research outputs found
Analytic Approximations for Transit Light Curve Observables, Uncertainties, and Covariances
The light curve of an exoplanetary transit can be used to estimate the
planetary radius and other parameters of interest. Because accurate parameter
estimation is a non-analytic and computationally intensive problem, it is often
useful to have analytic approximations for the parameters as well as their
uncertainties and covariances. Here we give such formulas, for the case of an
exoplanet transiting a star with a uniform brightness distribution. We also
assess the advantages of some relatively uncorrelated parameter sets for
fitting actual data. When limb darkening is significant, our parameter sets are
still useful, although our analytic formulas underpredict the covariances and
uncertainties.Comment: 33 pages, 14 figure
Spitzer and z' Secondary Eclipse Observations of the Highly Irradiated Transiting Brown Dwarf KELT-1b
We present secondary eclipse observations of the highly irradiated transiting
brown dwarf KELT-1b. These observations represent the first constraints on the
atmospheric dynamics of a highly irradiated brown dwarf, and the atmospheres of
irradiated giant planets at high surface gravity. Using the Spitzer Space
Telescope, we measure secondary eclipse depths of 0.195+/-0.010% at 3.6um and
0.200+/-0.012% at 4.5um. We also find tentative evidence for the secondary
eclipse in the z' band with a depth of 0.049+/-0.023%. These measured eclipse
depths are most consistent with an atmosphere model in which there is a strong
substellar hotspot, implying that heat redistribution in the atmosphere of
KELT-1b is low. While models with a more mild hotspot or even with dayside heat
redistribution are only marginally disfavored, models with complete heat
redistribution are strongly ruled out. The eclipse depths also prefer an
atmosphere with no TiO inversion layer, although a model with TiO inversion is
permitted in the dayside heat redistribution case, and we consider the
possibility of a day-night TiO cold trap in this object. For the first time, we
compare the IRAC colors of brown dwarfs and hot Jupiters as a function of
effective temperature. Importantly, our measurements reveal that KELT-1b has a
[3.6]-[4.5] color of 0.07+/-0.11, identical to that of isolated brown dwarfs of
similarly high temperature. In contrast, hot Jupiters generally show redder
[3.6]-[4.5] colors of ~0.4, with a very large range from ~0 to ~1. Evidently,
despite being more similar to hot Jupiters than to isolated brown dwarfs in
terms of external forcing of the atmosphere by stellar insolation, KELT-1b has
an atmosphere most like that of other brown dwarfs. This suggests that surface
gravity is very important in controlling the atmospheric systems of substellar
mass bodies.Comment: 14 pages, 3 tables, 11 figures. Accepted by ApJ. Updated to reflect
the accepted versio
Commentary: Essential Programs and Services Model
To further discussion about the Essential Programs and Services (EPS) model for funding public education in Maine, Maine Policy Review asked eight superintendentsārepresenting districts across the stateā to provide their views. We also asked each to discuss the needs of his district and whether additional state policy options were necessary to tackle the most pressing issues. The districts represented by these superintendents are a cross section of urban and rural high-receivers and low-receivers. Still, several commonalities emerge: the need for a state commitment that does not wax and wane with the business cycle; the urgency of professional development for new and experienced teachers; and, the importance of linking student outcomes with student assessment measures and student funding. In short, EPS is not seen as a solution to the stateās ongoing debate over public-education funding, but is recognized as a necessary first step
Diamagnetic Suppression of Component Magnetic Reconnection at the Magnetopause
We present particle-in-cell simulations of collisionless magnetic
reconnection in a system (like the magnetopause) with a large density asymmetry
across the current layer. In the presence of an ambient component of the
magnetic field perpendicular to the reconnection plane the gradient creates a
diamagnetic drift that advects the X-line with the electron diamagnetic
velocity. When the relative drift between the ions and electrons is of the
order the Alfven speed the large scale outflows from the X-line necessary for
fast reconnection cannot develop and the reconnection is suppressed. We discuss
how these effects vary with both the plasma beta and the shear angle of the
reconnecting field and discuss observational evidence for diamagnetic
stabilization at the magnetopause.Comment: 10 pages, 10 figures; accepted by JGR; agu2001.cls and agu.bst
include
KELT-10b: The First Transiting Exoplanet from the KELT-South Survey -- A Hot Sub-Jupiter Transiting a V = 10.7 Early G-Star
We report the discovery of KELT-10b, the first transiting exoplanet
discovered using the KELT-South telescope. KELT-10b is a highly inflated
sub-Jupiter mass planet transiting a relatively bright star (TYC
8378-64-1), with T = K, =
and [Fe/H] = , an inferred mass
M = M and radius R =
R. The planet has a radius R =
R and mass M =
M. The planet has an eccentricity consistent with zero and a semi-major
axis = AU. The best fitting linear
ephemeris is = 2457066.720450.00027 BJD and P =
4.16627390.0000063 days. This planet joins a group of highly inflated
transiting exoplanets with a radius much larger and a mass much less than those
of Jupiter. The planet, which boasts deep transits of 1.4%, has a relatively
high equilibrium temperature of T = K, assuming zero
albedo and perfect heat redistribution. KELT-10b receives an estimated
insolation of 10 erg s cm,
which places it far above the insolation threshold above which hot Jupiters
exhibit increasing amounts of radius inflation. Evolutionary analysis of the
host star suggests that KELT-10b is unlikely to survive beyond the current
subgiant phase, due to a concomitant in-spiral of the planet over the next
1 Gyr. The planet transits a relatively bright star and exhibits the
third largest transit depth of all transiting exoplanets with V 11 in the
southern hemisphere, making it a promising candidate for future atmospheric
characterization studies.Comment: 20 pages, 13 figures, 7 tables, accepted for publication in MNRA
A Human IgSF Cell-Surface Interactome Reveals a Complex Network of Protein-Protein Interactions
Cell-surface protein-protein interactions (PPIs) mediate cell-cell communication, recognition, and responses. We executed an interactome screen of 564 human cell-surface and secreted proteins, most of which are immunoglobulin superfamily (IgSF) proteins, using a high-throughput, automated ELISA-based screening platform employing a pooled-protein strategy to test all 318,096 PPI combinations. Screen results, augmented by phylogenetic homology analysis, revealed ā¼380 previously unreported PPIs. We validated a subset using surface plasmon resonance and cell binding assays. Observed PPIs reveal a large and complex network of interactions both within and across biological systems. We identified new PPIs for receptors with well-characterized ligands and binding partners for āorphanā receptors. New PPIs include proteins expressed on multiple cell types and involved in diverse processes including immune and nervous system development and function, differentiation/proliferation, metabolism, vascularization, and reproduction. These PPIs provide a resource for further biological investigation into their functional relevance and may offer new therapeutic drug targets
A Human IgSF Cell-Surface Interactome Reveals a Complex Network of Protein-Protein Interactions
Cell-surface protein-protein interactions (PPIs) mediate cell-cell communication, recognition, and responses. We executed an interactome screen of 564 human cell-surface and secreted proteins, most of which are immunoglobulin superfamily (IgSF) proteins, using a high-throughput, automated ELISA-based screening platform employing a pooled-protein strategy to test all 318,096 PPI combinations. Screen results, augmented by phylogenetic homology analysis, revealed ā¼380 previously unreported PPIs. We validated a subset using surface plasmon resonance and cell binding assays. Observed PPIs reveal a large and complex network of interactions both within and across biological systems. We identified new PPIs for receptors with well-characterized ligands and binding partners for āorphanā receptors. New PPIs include proteins expressed on multiple cell types and involved in diverse processes including immune and nervous system development and function, differentiation/proliferation, metabolism, vascularization, and reproduction. These PPIs provide a resource for further biological investigation into their functional relevance and may offer new therapeutic drug targets
KELT-3b: A Hot Jupiter Transiting a V=9.8 Late-F Star
We report the discovery of KELT-3b, a moderately inflated transiting hot
Jupiter with a mass of 1.477 (-0.067, +0.066) M_J, and radius of 1.345 +/-
0.072 R_J, with an orbital period of 2.7033904 +/- 0.000010 days. The host
star, KELT-3, is a V=9.8 late F star with M_* = 1.278 (-0.061, +0.063) M_sun,
R_* = 1.472 (-0.067, +0.065) R_sun, T_eff = 6306 (-49, +50) K, log(g) = 4.209
(-0.031, +0.033), and [Fe/H] = 0.044 (-0.082, +0.080), and has a likely proper
motion companion. KELT-3b is the third transiting exoplanet discovered by the
KELT survey, and is orbiting one of the 20 brightest known transiting planet
host stars, making it a promising candidate for detailed characterization
studies. Although we infer that KELT-3 is significantly evolved, a preliminary
analysis of the stellar and orbital evolution of the system suggests that the
planet has likely always received a level of incident flux above the
empirically-identified threshold for radius inflation suggested by Demory &
Seager (2011).Comment: 12 pages, 12 figures, accepted to Ap
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