304 research outputs found
The Transit Light Source Effect: False Spectral Features and Incorrect Densities for M-dwarf Transiting Planets
Transmission spectra are differential measurements that utilize stellar
illumination to probe transiting exoplanet atmospheres. Any spectral difference
between the illuminating light source and the disk-integrated stellar spectrum
due to starspots and faculae will be imprinted in the observed transmission
spectrum. However, few constraints exist for the extent of photospheric
heterogeneities in M dwarfs. Here, we model spot and faculae covering fractions
consistent with observed photometric variabilities for M dwarfs and the
associated 0.3-5.5 m stellar contamination spectra. We find that large
ranges of spot and faculae covering fractions are consistent with observations
and corrections assuming a linear relation between variability amplitude and
covering fractions generally underestimate the stellar contamination. Using
realistic estimates for spot and faculae covering fractions, we find stellar
contamination can be more than larger than transit depth changes
expected for atmospheric features in rocky exoplanets. We also find that
stellar spectral contamination can lead to systematic errors in radius and
therefore the derived density of small planets. In the case of the TRAPPIST-1
system, we show that TRAPPIST-1's rotational variability is consistent with
spot covering fractions and faculae covering
fractions . The associated stellar contamination
signals alter transit depths of the TRAPPIST-1 planets at wavelengths of
interest for planetary atmospheric species by roughly 1-15 the
strength of planetary features, significantly complicating follow-up
observations of this system. Similarly, we find stellar contamination can lead
to underestimates of bulk densities of the TRAPPIST-1 planets of , thus leading to overestimates of their volatile contents.Comment: accepted for publication in Ap
Quantum chaos in one dimension?
In this work we investigate the inverse of the celebrated
Bohigas-Giannoni-Schmit conjecture. Using two inversion methods we compute a
one-dimensional potential whose lowest N eigenvalues obey random matrix
statistics. Our numerical results indicate that in the asymptotic limit,
N->infinity, the solution is nowhere differentiable and most probably nowhere
continuous. Thus such a counterexample does not exist.Comment: 7 pages, 10 figures, minor correction, references extende
Approximation of Top Lyapunov Exponent of Stochastic Delayed Turning Model Using Fokker-Planck Approach
StochasticDelayDiffEq.jl - An Integrator Interface for Stochastic Delay Differential Equations in Julia
Methods for easy recognition of isostructurality – lab jack-like crystal structures of halogenated 2-phenylbenzimidazoles
Easy recognition and numerical description of isostructurality; how different the similar structures can be; supramolecular aspects of isostructurality
Xylan-Degrading Catalytic Flagellar Nanorods
Flagellin, the main component of flagellar filaments, is a protein possessing polymerization ability. In this work, a novel fusion construct of xylanase A from B. subtilis and Salmonella flagellin was created which is applicable to build xylan-degrading catalytic nanorods of high stability. The FliC-XynA chimera when overexpressed in a flagellin deficient Salmonella host strain was secreted into the culture medium by the flagellum-specific export machinery allowing easy purification. Filamentous assemblies displaying high surface density of catalytic sites were produced by ammonium sulfate-induced polymerization. FliC-XynA nanorods were resistant to proteolytic degradation and preserved their enzymatic activity for a long period of time. Furnishing enzymes with self-assembling ability to build catalytic nanorods offers a promising alternative approach to enzyme immobilization onto nanostructured synthetic scaffolds
Subexponential Parameterized Algorithms for Planar and Apex-Minor-Free Graphs via Low Treewidth Pattern Covering
We prove the following theorem. Given a planar graph and an integer ,
it is possible in polynomial time to randomly sample a subset of vertices
of with the following properties: (i) induces a subgraph of of
treewidth , and (ii) for every connected subgraph
of on at most vertices, the probability that covers the whole
vertex set of is at least , where is the number of vertices of .
Together with standard dynamic programming techniques for graphs of bounded
treewidth, this result gives a versatile technique for obtaining (randomized)
subexponential parameterized algorithms for problems on planar graphs, usually
with running time bound . The technique can be applied to problems expressible as
searching for a small, connected pattern with a prescribed property in a large
host graph, examples of such problems include Directed -Path, Weighted
-Path, Vertex Cover Local Search, and Subgraph Isomorphism, among others. Up
to this point, it was open whether these problems can be solved in
subexponential parameterized time on planar graphs, because they are not
amenable to the classic technique of bidimensionality. Furthermore, all our
results hold in fact on any class of graphs that exclude a fixed apex graph as
a minor, in particular on graphs embeddable in any fixed surface
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