23,328 research outputs found
Physical properties and radius variations in the HAT-P-5 planetary system from simultaneous four-colour photometry
No full textThe radii of giant planets, as measured from transit observations, may vary with wavelength due to Rayleigh scattering or variations in opacity. Such an effect is predicted to be large enough to detect using ground-based observations at multiple wavelengths. We present the defocused photometry of a transit in the HAT-P-5 system, obtained simultaneously through Strömgren u, Gunn g and r, and Johnson I filters. Two more transit events were observed through a Gunn r filter. We detect a substantially larger planetary radius in u, but the effect is greater than predicted using theoretical model atmospheres of gaseous planets. This phenomenon is most likely to be due to systematic errors present in the u-band photometry, stemming from variations in the transparency of Earth’s atmosphere at these short wavelengths. We use our data to calculate an improved orbital ephemeris and to refine the measured physical properties of the system. The planet HAT-P-5 b has a mass of and a radius of (statistical and systematic errors, respectively), making it slightly larger than expected according to standard models of coreless gas-giant planets. Its equilibrium temperature of 1517 ± 29 K is within 60 K of that of the extensively studied planet HD 209458 b
Revising the properties of low mass eclipsing binary stars using TESS light curves
No full textPrecise measurements of stellar parameters are required in order to develop our theoretical understanding of stellar structure. These measurements enable errors and uncertainties to be quantified in theoretical models and constrain the physical interpretation of observed phenomena, such as the inflated radii of low-mass stars. We use newly-available TESS (Transiting Exoplanet Satellite Survey) light curves combined with published radial velocity measurements to improve the characterization of 12 low mass eclipsing binaries composed of an M dwarf accompanied by a brighter F/G star. We present and analyse ground-based simultaneous four-colour photometry for two targets. Our results include the first measurements of the fundamental properties of two of the systems. Light curve and radial velocity information were converted into the physical parameters of each component of the systems using an isochrone fitting method. We also derive the effective temperatures of the M dwarfs, almost tripling the number of such measurements. The results are discussed in the context of radius inflation. We find that exquisite precision in the age estimation of young objects is required to determine their inflation status. However, all but three of the objects are securely located among the main sequence, demonstrating radius inflation and the necessity to develop our understanding of the complex physical processes governing the evolution of low-mass stars. We investigated the hypothesis that luminosity is unaffected by the inflation problem but the findings were not conclusive
CWRML: representing crop wild relative conservation and use data in XML
No full textBackground
Crop wild relatives are wild species that are closely related to crops. They are valuable as potential gene donors for crop improvement and may help to ensure food security for the future. However, they are becoming increasingly threatened in the wild and are inadequately conserved, both in situ and ex situ. Information about the conservation status and utilisation potential of crop wild relatives is diverse and dispersed, and no single agreed standard exists for representing such information; yet, this information is vital to ensure these species are effectively conserved and utilised. The European Community-funded project, European Crop Wild Relative Diversity Assessment and Conservation Forum, determined the minimum information requirements for the conservation and utilisation of crop wild relatives and created the Crop Wild Relative Information System, incorporating an eXtensible Markup Language (XML) schema to aid data sharing and exchange.
Results
Crop Wild Relative Markup Language (CWRML) was developed to represent the data necessary for crop wild relative conservation and ensure that they can be effectively utilised for crop improvement. The schema partitions data into taxon-, site-, and population-specific elements, to allow for integration with other more general conservation biology schemata which may emerge as accepted standards in the future. These elements are composed of sub-elements, which are structured in order to facilitate the use of the schema in a variety of crop wild relative conservation and use contexts. Pre-existing standards for data representation in conservation biology were reviewed and incorporated into the schema as restrictions on element data contents, where appropriate.
Conclusion
CWRML provides a flexible data communication format for representing in situ and ex situ conservation status of individual taxa as well as their utilisation potential. The development of the schema highlights a number of instances where additional standards-development may be valuable, particularly with regard to the representation of population-specific data and utilisation potential. As crop wild relatives are intrinsically no different to other wild plant species there is potential for the inclusion of CWRML data elements in the emerging standards for representation of biodiversity data
The L-p-to-L-q boundedness of commutators with applications to the Jacobian operator
No full textSupplying the missing necessary conditions, we complete the characterisation of the L-p -> L-q boundedness of commutators [b, T] of pointwise multiplication and Calderon-Zygmund operators, for arbitrary pairs of 1 q, our results are new even for special classical operators with smooth kernels. As an application, we show that every f is an element of L-p(R-d) can be represented as a convergent series of normalised Jacobians J(u) = det del uof u is an element of (over dot(W))(1,dp)(R-d)(d). This extends, from p = 1 to p > 1, a result of Coifman, Lions, Meyer and Semmes about J:. (over dot(W))(1,d)(R-d)(d) -> H-1(R-d), and supports a conjecture of Iwaniec about the solvability of the equation Ju = f is an element of L-p(R-d). (C) 2021 The Author(s). Published by Elsevier Masson SAS.Peer reviewe
Stellar limb darkening. A new MPS-ATLAS library for Kepler, TESS, CHEOPS, and PLATO passbands
No full textThe detection of the first exoplanet paved the way into the era of transit
photometry space missions with a revolutionary photometric precision that aim
at discovering new exoplanetary systems around different types of stars. With
this high precision, it is possible to derive very accurately the radii of
exoplanets which is crucial for constraining their type and composition.
However, it requires an accurate description of host stars, especially their
center-to-limb variation of intensities (so called limb darkening) as it
affects the planet-to-star radius ratio determination. We aim at improving the
accuracy of limb darkening calculations for stars with a wide range of
fundamental parameters. We used the recently developed 1D MPS-ATLAS code to
compute model atmosphere structures and to synthesize stellar limb darkening on
a very fine grid of stellar parameters. For the computations we utilized the
most accurate information on chemical element abundances and mixing length
parameters including convective overshoot. The stellar limb darkening was
fitted using the two most accurate limb darkening laws: the power-2 and
4-parameters non-linear laws. We present a new extensive library of stellar
model atmospheric structures, the synthesized stellar limb darkening curves,
and the coefficients of parameterized limb-darkening laws on a very fine grid
of stellar parameters in the Kepler, TESS, CHEOPS, and PLATO passbands. The
fine grid allows overcoming the sizable errors introduced by the need to
interpolate. Our computations of solar limb darkening are in a good agreement
with available solar measurements at different view angles and wavelengths. Our
computations of stellar limb darkening agree well with available measurements
of Kepler stars. A new grid of stellar model structures, limb darkening and
their fitted coefficients in different broad filters is provided in CDS.Comment: 19 pages, 17 figures, accepted to Astronomy and Astrophysics. All
tables are available in CD
Logarithmic variance profiles and the corresponding f-1 spectra of temperature fluctuations in turbulent Rayleigh-Bénard convection
No full textWe report experimental results for the temperature variance 2(z) and the corresponding frequency spectra P(f) in turbulent Rayleigh-Bénard convection (RBC) in a cylindrical sample of aspect ratioT= D/L = 1:00 (D = 1:12 m is the diameter and L = 1:12 m the height). The measurements were conducted in the Rayleigh-number range 1011 < Ra < 1:35 1014 and Pr ' 0:8. For Ra = 1:35x1014, 2(z) could be described well by a logarithmic dependence on the vertical position z in a range of z 1 < z < z 2 with z 1 ' 70 and z 2 = 0:1L. Here L=(2Nu) is the thickness of a thin thermal sublayer adjacent to the horizontal plate where the heat flux (denoted by the Nusselt number Nu) is carried mostly by thermal diffusion. In the log layer, we found that the temperature spectra had a significant frequency range over which P(f) f with close to 1. As Ra decreased, increased so that the log layer became thinner. At Ra = 2:05 1011, z 2 < z 1 and therefore there was no range for a log layer. Correspondingly, the temperature spectrum near the horizontal plate did not have the f1 scaling form either
Equivalence of measures of smoothness in L > p(Sd-1), 1 < p < infinity
No full textNSERC [G121211001, A4816.]Suppose (Delta) over tilde is the Laplace-Beltrami operator on the sphere S(d-1), Delta(k)(p) f(x) = Delta(p)Delta(k-1)(p)f(x) and Delta(p)f (x) = f(px) - f (x) where p is an element of SO(d). omega(m)(f,t) L(p)(S(d-1)) equivalent to sup{parallel to Delta(m)(p)f parallel to L(p)(S(d-1)) : rho is an element of SO(d), max(x is an element of Sd-1) rho x . x >= cost} and (K) over tilde (m()f,t(m))(p) equivalent to inf{parallel to f - g parallel to L(p)(S(d-1)) + t(m) parallel to(-(Delta) over tilde (m/2)g parallel to L(p)(S(d-1)) : g is an element of D((-(Delta) over tilde)(m/2))} are equivalent for 1 < p < infinity. We note that for even m the relation was recently investigated by the second author. The equivalence yields an extension of the results on sharp Jackson inequalities on the sphere. A new strong converse inequality for L(p)(S(d-1)) given in this paper plays a significant role in the proof
l-modular blocks of Rep_k(SL_n(F))
No full textLet F be a non-archimedean local field with residual characteristic p, and k an algebraically closed field with characteristic l, where l different from p. Let Rep_k(SL_n(F)) be the category of smooth k-representations of SL_n(F). In this work, we establish the block decomposition of Rep_k(SL_n(F)) under the condition that p does not divide the order of the Weyl group of SL_n(F).Affiliation changed. The author corrects some errors in section 4 and section 5 in the previous versio
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
On conditional expectations in L <sup>p</sup> (μ; L <sup>q</sup> (ν; X))
No full text Let (A, A, μ) and (B, B, ν) be probability spaces, let F be a sub-σ-algebra of the product σ-algebra A× B, let X be a Banach space and let 1 < p, q< ∞. We obtain necessary and sufficient conditions in order that the conditional expectation with respect to F defines a bounded linear operator from L p (μ; L q (ν; X)) onto LFp(μ;Lq(ν;X)), the closed subspace in L p (μ; L q (ν; X)) of all functions having a strongly F-measurable representative. Analysi
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