ABSTRACT
Phase curves of asteroids are typically considered to depend solely on the scattering properties of airless particulate surfaces and the size of the object being studied. In this study, we ...demonstrate the additional dependence of phase curves on object shape, rotation pole orientation, and viewing geometry over an apparition. Variations in the phase curve of near-Earth asteroid (159402) 1999 AP10 over its apparition from 2020 July to 2021 January are verified to be due to aspect changes over the apparition. This is achieved through shape modelling of the asteroid and simulation of the phase curve over the apparition. We present simulations of asteroid phase curves over a range of geometries to understand the potential magnitude of this aspect effect, and under which circumstances it can begin to dominate in the phase curves. This dependence on aspect may introduce significant additional uncertainty in the properties derived from phase-curve data. We provide and demonstrate software code to estimate the aspect-related uncertainty in near-Earth asteroid phase curves through simulation and model fitting of a randomly generated sample of ellipsoidal asteroid models over the observed viewing geometry. We demonstrate how ignoring this effect may lead to misleading interpretations of the data and underestimation of uncertainties in further studies, such as those in the infrared that use phase curve derived parameters when fitting physical properties of an asteroid.
Building on previous work, a new search of the SuperWASP archive was carried out to identify eclipsing binary systems near the short-period limit. 143 candidate objects were detected with orbital ...periods between 16 000 and 20 000 s, of which 97 are new discoveries. Period changes significant at 1σ or more were detected in 74 of these objects, and in 38 the changes were significant at 3σ or more. The significant period changes observed followed an approximately normal distribution with a half-width at half-maximum of ~0.1 s yr-1. There was no apparent relationship between period length and magnitude or direction of period change. Amongst several interesting individual objects studied, 1SWASP J093010.78+533859.5 is presented as a new doubly eclipsing quadruple system, consisting of a contact binary with a 19 674.575 s period and an Algol-type binary with a 112 799.109 s period, separated by 66.1 AU, being the sixth known system of this type.
We discuss the properties of 137 cataclysmic variables (CVs) which are included in the Sloan Digital Sky Survey (SDSS) spectroscopic data base, and for which accurate orbital periods have been ...measured. 92 of these systems are new discoveries from SDSS and were followed-up in more detail over the past few years. 45 systems were previously identified as CVs because of the detection of optical outbursts and/or X-ray emission, and subsequently re-identified from the SDSS spectroscopy. The period distribution of the SDSS CVs differs dramatically from that of all the previously known CVs, in particular it contains a significant accumulation of systems in the orbital period range 80–86 min. We identify this feature as the elusive ‘period minimum spike’ predicted by CV population models, which resolves a long-standing discrepancy between compact binary evolution theory and observations. We show that this spike is almost entirely due to the large number of CVs with very low accretion activity identified by SDSS. The optical spectra of these systems are dominated by emission from the white dwarf photosphere, and display little or no spectroscopic signature from the donor stars, suggesting very low mass companion stars. We determine the average absolute magnitude of these low-luminosity CVs at the period minimum to be 〈Mg〉= 11.6 ± 0.7. Comparison of the SDSS CV sample to the CVs found in the Hamburg Quasar Survey and the Palomar Green Survey suggests that the depth of SDSS is the key ingredient resulting in the discovery of a large number of intrinsically faint short-period systems.
We apply population synthesis techniques to calculate the present-day population of post-common envelope binaries (PCEBs) for a range of theoretical models describing the common envelope (CE) phase. ...Adopting the canonical energy budget approach, we consider models where the ejection efficiency αCE is either a constant or a function of the secondary mass. We obtain the envelope binding energy from detailed stellar models of the progenitor primary, with and without the thermal and ionization energy, but we also test a commonly used analytical scaling. We also employ the alternative angular momentum budget approach, known as the γ-algorithm. We find that a constant, global value of αCE≳ 0.1 can adequately account for the observed population of PCEBs with late spectral-type secondaries. However, this prescription fails to reproduce IK Pegasi (IK Peg), which has a secondary with spectral type A8. We can account for IK Peg if we include thermal and ionization energy of the giant's envelope, or if we use the γ-algorithm. However, the γ-algorithm predicts local space densities that are 1 to 2 orders of magnitude greater than estimates from observations. In contrast, the canonical energy budget prescription with an initial mass ratio distribution that favours unequal initial mass ratios (n(qi) ∝q−0.99i) gives a local space density which is in good agreement with observations, and best reproduces the observed distribution of PCEBs. Finally, all models fail to reproduce the sharp decline for orbital periods, Porb≳ 1 d in the orbital period distribution of observed PCEBs, even if we take into account selection effects against systems with long orbital periods and early spectral-type secondaries.
We initiated a comprehensive state of the art binary population synthesis study of white dwarf main-sequence star (WDMS) binaries to serve as a foundation for subsequent studies on pre-cataclysmic ...variables, double white dwarfs, and white dwarf + B-star binaries. We considered seven distinct formation channels subdivided into three main groups according to the evolutionary process that gives rise to the formation of the white dwarf or its helium-star progenitor: dynamically stable Roche-lobe overflow (Algol-type evolution), dynamically unstable Roche-lobe overflow (common-envelope evolution), or stellar winds (single star evolution). For each formation channel, we examine the sensitivity of the population to changes in the amount of mass lost from the system during dynamically stable Roche-lobe overflow, the common-envelope ejection efficiency, and the initial mass ratio or initial secondary mass distribution. In the case of a flat initial mass ratio distribution, the local space density of WDMS binaries is of the order of ~$10^{-3}\,{\rm pc}^{-3}$. This number decreases to ~$10^{-4}\,{\rm pc}^{-3}$ when the initial mass ratio distribution is approximately proportional to the inverse of the initial mass ratio. More than 75% of the WDMS binary population originates from wide systems in which both components essentially evolve as if they were single stars. The remaining part of the population is dominated by systems in which the white dwarf is formed in a common-envelope phase when the primary ascends the first giant branch or the asymptotic giant branch. When dynamically stable mass transfer proceeds highly conservative and the common-envelope ejection process is very efficient, the birthrate of WDMS binaries forming through a common-envelope phase is about 10 times larger than the birthrate of WDMS binaries forming through a stable Roche-lobe overflow phase. The ratio of the number of helium white dwarf systems to the number of carbon/oxygen or oxygen/neon/magnesium white dwarf systems derived from large samples of observed WDMS binaries by, e.g., future planet-search missions such as SuperWASP, COROT, and Kepler may furthermore constrain the common-envelope ejection efficiency.
•Nano crystalline material structure determination limits X-ray powder diffraction.•Small grain size leads to peak broadening, preferred orientation to missing data.•Combining ADT and XRPD overcomes ...these limitations.
In this paper the reliability of structure solution of nano-crystalline porous compounds with preferred orientation based on automated electron diffraction tomography (ADT) is discussed. It will be shown that the limitations of the data acquisition geometry can be overcome by completing the missing diffraction data with additional diffraction information. Apart from different ways of sample preparation, data merging with either additional ADT data sets or intensities derived from X-ray powder diffraction comprise an effective way to improve the accuracy of the structure solution.
ABSTRACT
We present the discovery of two new hot Jupiters identified from the Wide-Angle Search for Planets (WASP) survey, WASP-186b and WASP-187b (TOI-1494.01 and TOI-1493.01). Their planetary ...nature was established from SOPHIE spectroscopic observations, and additional photometry was obtained from Transiting Exoplanet Survey Satellite. Stellar parameters for the host stars are derived from spectral line, infrared flux method, and isochrone placement analyses. These parameters are combined with the photometric and radial velocity data in a Markov chain Monte Carlo method to determine the planetary properties. WASP-186b is a massive Jupiter (4.22 ± 0.18 MJ, 1.11 ± 0.03 RJ) orbiting a mid-F star on a 5.03-d eccentric (e = 0.327 ± 0.008) orbit. WASP-187b is a low-density (0.80 ± 0.09 MJ, 1.64 ± 0.05 RJ) planet in a 5.15-d circular orbit around a slightly evolved early F-type star.
•Comparison of solid state properties of iron oxide/hydroxide nanoparticle products.•Structural analysis allows prediction of stability including labile iron content.•ED and XRPD represent useful ...techniques to characterize complex iron formulations.
Drug products containing iron oxide and hydroxide nanoparticles (INPs) are important for the treatment of iron deficiency anaemia. Pharmaceuticals prepared by the complexation of different kinds of INPs and carbohydrates have different physicochemical and biopharmaceutic characteristics. The increasing number of parenteral non-biological complex drugs (NBCD) containing iron requires physicochemical methods for characterization and enabling of cross comparisons. In this context the structure and the level of crystallinity of the iron phases may be connected to the in vitro and in vivo dissolution rates, which etiologically determine the therapeutic and toxic effects.
X-ray powder diffraction (XRPD) and electron diffraction (ED) methods were used in order to investigate the nine different parenteral iron formulations Ferumoxytol (Feraheme®), sodium ferric gluconate sucrose (Ferrlecit®), iron sucrose (Venofer®), low molecular weight iron dextran (CosmoFer®), low molecular weight iron dextran (Infed®), high molecular weight iron dextran (Ironate®), high molecular weight iron dextran (Dexferrum®), iron carboxymaltose (Ferinject®) and iron isomaltoside 1000 (Monofer®).
The iron phase in CosmoFer®, Ferinject®, Monofer®, Infed®, Ironate® and Dexferrum® was identified as Akaganéite/Akaganéite-like (β-FeOOH), with low amounts of chloride. By combining results of both methods the iron oxide in Feraheme® was identified as Magnetite (Fe3O4) with spinel-like structure. Ferrlecit® and Venofer® were difficult to analyze due to the low degree of crystallinity, but the iron phase seems to fit Lepidocrocite/Lepidocrocite-like (γ-FeOOH) or an amorphous kind of structure. The structural information on the type of iron oxide or hydroxide together with the particle size allows predicting the stability of the different complexes including their labile iron content. The combination of ED and XRPD methods is a very helpful approach especially for structural analysis of nanoscopic or low crystalline materials.
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