On the (anticipated) diversity of terrestrial planet atmospheres

On our way toward the characterization of smaller and more temperate planets, missions dedicated to the spectroscopic observation of exoplanets will teach us about the wide diversity of classes of planetary atmospheres, many of them probably having no equivalent in the Solar System. But what kind of atmospheres can we expect? To start answering this question, many theoretical studies have tried to understand and model the various processes controlling the formation and evolution of planetary atmospheres, with some success in the Solar System. Here, we shortly review these processes and we try to give an idea of the various type of atmospheres that these processes can create. As will be made clear, current atmosphere evolution models have many shortcomings yet, and need heavy calibrations. With that in mind, we will thus discuss how observations with a mission similar to EChO would help us unravel the link between a planet’s environment and its atmosphere.     

Zatrikean pre-geometry as a tool for modelling in theoretical astrophysics

In this paper, we present an axiomatic foundation on zatrikean (i.e., chess-like) pre-geometry. Furthermore, we find that rotation can induce such a pre-geometry; and this rotationally induced zatrikean pre-geometry can, in turn, decisively affect all the interrelated physical phenomena, which in their majority are significant for theoretical astrophysics and cosmology.     

Secrets of E2V Technologies CCDs (ex Marconi CCDs)

To complement previously published information on E2V CCDs, we present here some less well-known information about Marconi CCDs. We show details of the performance of deep depletion silicon variants, and discuss other subtleties of performance. We also present an update on L3vision (sub-electron noise) devices, indicating current availability, options, and ongoing development work. Finally, we will give a flavour of the range of custom designs that have been made. Many of these are not commercially available, and may not be familiar to all astronomers or CCD technologists. This revised version was published online in July 2006 with corrections to the Cover Date.     

Gamma-ray detectors (>10MeV)

Photons in the energy region above 10 MeV can provide unique information about the highest energy particles produced in solar flares. Measurements of the energy spectra, temporal behavior and anisotropies of the incident photons, can give valuable insights into the particle acceleration process. In this paper we review the detection techniques used at these energies, typical instruments which use these techniques, and future solar missions both actual and potential.     

Measurements of methane absorption by the descent imager/spectral radiometer (DISR) during its descent through Titan's atmosphere

New low-temperature methane absorption coefficients pertinent to the Titan environment are presented as derived from the Huygens DISR spectral measurements combined with the in-situ measurements of the methane gas abundance profile measured by the Huygens Gas Chromatograph/Mass Spectrometer (GCMS). The visible and near-infrared spectrometers of the descent imager/spectral radiometer (DISR) instrument on the Huygens probe looked upward and downward covering wavelengths from 480 to 1620 nm at altitudes from 150 km to the surface during the descent to Titan's surface. The measurements at continuum wavelengths were used to determine the vertical distribution, single-scattering albedos, and phase functions of the aerosols. The gas chromatograph/mass spectrometer (GCMS) instrument on the probe measured the methane mixing ratio throughout the descent. The DISR measurements are the first direct measurements of the absorbing properties of methane gas made in the atmosphere of Titan at the pathlengths, pressures, and temperatures that occur there. Here we use the DISR spectral measurements to determine the relative methane absorptions at different wavelengths along the path from the probe to the sun throughout the descent. These transmissions as functions of methane path length are fit by exponential sums and used in a haze radiative transfer model to compare the results to the spectra measured by DISR. We also compare the recent laboratory measurements of methane absorption at low temperatures [Irwin et al., 2006. Improved near-infrared methane band models and k-distribution parameters from 2000 to 9500 cm⁻¹ and implications for interpretation of outer planet spectra. Icarus 181, 309-319] with the DISR measurements. We find that the strong bands formed at low pressures on Titan act as if they have roughly half the absorption predicted by the laboratory measurements, while the weak absorption regions absorb considerably more than suggested by some extrapolations of warm measurements to the cold Titan temperatures. We give factors as a function of wavelength that can be used with the published methane coefficients between 830 and 1620 nm to give agreement with the DISR measurements. We also give exponential sum coefficients for methane absorptions that fit the DISR observations. We find the DISR observations of the weaker methane bands shortward of 830 nm agree with the methane coefficients given by Karkoschka [1994. Spectrophotometry of the jovian planets and Titan at 300- to 1000-nm wavelength: the methane spectrum. Icarus 111, 174-192]. Finally, we discuss the implications of our results for computations of methane absorption in the atmospheres of the outer planets.     

X-ray measurements of black hole X-ray binary source GRS 1915+105 and the evolution of hard X-ray spectrum

We report the spectral measurement of GRS 1915+105 in the hard X-ray energy band of 20–140keV. The observations were made on March 30th, 1997 during a quiescent phase of the source. We discuss the mechanism of emission of hard X-ray photons and the evolution of the spectrum by comparing the data with earlier measurements and an axiomatic model for the X-ray source.     

The Ushnus in the astronomy of the Inca culture

Inferences are made about the relationship that existed between the Ushnus, pyramid-shaped, terraced structures used by the Incas in the most important ceremonies of the Tawantinsuyo, and Inka Astronomy. We draw attention to Ayni, Kawsaypacha, Duality, and Tinkuy principles, multidimensional codes of conduct and wisdom that are at the root of the Andean cosmovision and on their perception of the world and the Cosmos. These principles, examined as postulates, allow to elaborate axiomatic propositions to identify the Ushnus with ancient Astronomy practices. In a complementary statement, starting from a bi-conditional proposition, we may infer through reciprocal corollaries that the Inka earliest roots to a holistic learning and educational ambient in the Tawantinsuyo was not elitist, instead it was based on a epistemological construct that differs from the corresponding Western educational ambients. An epistemological and cognitive approach allows to identify an ancient elaborate process of knowledge construction, based on the four fundamental principles, corresponding to different levels of assimilation and comprehension. As a complementary aspect, we identify some of the most preserved Ushnus of the Inka “Empire.” Then we complement this contribution with a broader interpretation for the Ushnus.     

Secular Effects on Orbits of Binary Stars Induced by Temporal Variation of Gravitational Constant (Case for Elliptical Orbit)

In this paper we investigate the influence of a varying gravitation constant on the orbits of celestial bodies. Regarding the eccentric anomaly as an independent variable, we find the solutions to the perturbed equations of motion. In the first order solutions, we find the secular and periodic variations in semi-major axis. For the other orbital elements only periodic variations exhibit. However in the second order solutions, the longitude of periastron and the mean longitude have secular terms. Applying the calculations to six selected binaries, we give the numerical estimations of the variations of orbits. These results are then carefully compared and discussed.     

Arc(let)s in clusters of galaxies

Summary The discovery of giant gravitational arcs and arclets in rich clusters of galaxies is one of the major events of the last decade in observational cosmology. High resolution imaging in subarcsecond seeing conditions of giant arcs gives information on the cluster potential and the matter distribution within the inner regions of clusters. Ultra-deep photometry of the clusters reveals numerous arclets with an orthoradial orientation from which one can infer the projected mass profile at large distance and the redshift distribution of the faintest distant background galaxies which are unobservable with standard spectroscopic techniques. Thanks to the strong magnification factor, the spectroscopy of giant arcs is possible and we can therefore observe with great detail a few very distant galaxies. Individual redshifts of arcs give the total mass of the lens, whereas the spectroscopy of a large sample of arcs also gives information on the redshift distribution of distant galaxies. It is obvious that cluster lenses play an important role as large natural telescopes for probing the distant universe. Finally, observations of multiple-arc configurations due to different sources may even constrain the cosmological parameters. We are now confident that gravitational lensing will be an essential tool within the next decade for observing very high redshift galaxies and the weak shear generated by the largest structures of the universe.In this review we summarize the present status of gravitational arc(let)s surveys with particular emphasis on the most important issues which have arisen during the last years and on the prospects for the future, regarding the rebirth of the Hubble Space Telescope, the coming of a new generation of Very Large Telescopes, and the development of large CCDs in the optical and the infrared.     

The influence of turbulence pressure on the late stages of evolution of medium and small mass stars (I) Calculation of the turbulence pressure, equation of state and thermodynamic quantities

Using the mixing length theory we give expressions for turbulence pressure and the equation of state and various thermodynamic quantities when turbulence is included. On this basis we examined the size of turbulence in the evolution of two stars of masses 2.8 and 7.0M from the main sequence to the red giant and the AGB stages, Our results show that in the late stages the turbulence pressure near the surface of the star can be as much as 30% of the total pressure.     

Magnetic,chemically peculiar (CP2) stars in the SuperWASP survey

The magnetic chemically peculiar (CP2) stars of the upper main sequence are well‐suited for investigating the impact of magnetic fields on the surface layers of stars, which leads to abundance inhomogeneities (spots) resulting in photometric variability. The light changes are explained in terms of the oblique rotator model; the derived photometric periods thus correlate with the rotational periods of the stars. CP2 stars exhibiting this kind of variability are classified as α² Canum Venaticorum (ACV) variables. We have analysed around 3850000 individual photometric WASP measurements of magnetic chemically peculiar (CP2) stars and candidates selected from the catalogue of Ap, HgMn, and Am stars, with the ultimate goal of detecting new ACV variables. In total, we found 80 variables, from which 74 are reported here for the first time. The data allowed us to establish variability for 23 stars which had been reported as probably constant in the literature before. Light curve parameters were obtained for all stars by a least‐squares fit with the fundamental sine wave and its first harmonic. Because of the scarcity of Strömgren uvbyβ measurements and the lack of parallax measurements with an accuracy better than 20%, we are not able to give reliable astro‐physical parameters for the investigated objects. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The remarkable surface homogeneity of the Dawn mission target (1) Ceres

Dwarf-planet (1) Ceres is one of the two targets, along with (4) Vesta, that will be studied by the NASA Dawn spacecraft via imaging, visible and near-infrared spectroscopy, and gamma-ray and neutron spectroscopy. While Ceres’ visible and near-infrared disk-integrated spectra have been well characterized, little has been done about quantifying spectral variations over the surface. Any spectral variation would give us insights on the geographical variation of the composition and/or the surface age. The only work so far was that of Rivkin and Volquardsen ([2010], Icarus 206, 327) who reported rotationally-resolved spectroscopic (disk-integrated) observations in the 2.2–4.0 μm range; their observations showed evidence for a relatively uniform surface.Here, we report disk-resolved observations of Ceres with SINFONI (ESO VLT) in the 1.17–1.32 μm and 1.45–2.35 μm wavelength ranges. The observations were made under excellent seeing conditions (0.6″), allowing us to reach a spatial resolution of ～75 km on Ceres’ surface. We do not find any spectral variation above a 3% level, suggesting a homogeneous surface at our spatial resolution. Slight variations (about 2%) of the spectral slope are detected, geographically correlated with the albedo markings reported from the analysis of the HST and Keck disk-resolved images of Ceres (Li et al. [2006], Icarus 182, 143; Carry et al. [2008], Astron. Astrophys. 478, 235). Given the lack of constraints on the surface composition of Ceres, however, we cannot assert the causes of these variations.     

Zatrikean pre-geometry: number of alyssoids and the dilation factors

This paper is the continuation of a recent paper (written by the first author), in which an axiomatic zatrikean (i.e., chess-like) pre-geometry together with a rotationally induced zatrikean pre-geometry were developed. In the present paper, the number of alyssoids joining two geobits is determined for bothQ andR pre-metrics. Furthermore, the functional forms ofQ andR pre-geometric dilation factors are determined and calculated. It has been verified that these functions contain discontinuities and, therefore, a method for smoothing them out is proposed and applied.     

Investigation of the substructure of clusters of galaxies by the method ofS-tree diagrams: Non-point approximation

Further development of the method of S-tree diagrams for studying the hierarchical structure of dusters of galaxies is presented. First, we give a generalization for a system of N spheres, i.e., we make the transition to non-point models, and describe a method of constructing a new corresponding matrix D. Second, we give an algorithm for analyzing information obtained by the method of S-tree diagrams. This algorithm makes it possible to determine the hierarchical substructure and composition of each subgroup of the investigated system. Translated from Astrofizika, Vol. 40, No. 3, pp. 425–432, August, 1997.     

Three-Dimensional (3-D) Reconstructions of EISCAT IPS Velocity Data in the Declining Phase of Solar Cycle 23

The European Incoherent SCATter (EISCAT) radar has been used for remote-sensing observations of interplanetary scintillation (IPS) for a quarter of a century. During the April/May 2007 observing campaign, a large number of observations of IPS using EISCAT took place to give a reasonable spatial and temporal coverage of solar wind velocity structure throughout this time during the declining phase of Solar Cycle 23. Many co-rotating and transient features were observed during this period. Using the University of California, San Diego three-dimensional (3-D) time-dependent computer assisted tomography (C.A.T.) solar-wind reconstruction analysis, we show the velocity structure of the inner heliosphere in three dimensions throughout the time interval of 20 April through 20 May 2007. We also compare to white-light remote-sensing observations of an interplanetary coronal mass ejection (ICME) seen by the STEREO Ahead spacecraft inner Heliospheric Imager on 16 May 2007, as well as to in-situ solar-wind measurements taken with near-Earth spacebourne instrumentation throughout this interval. The reconstructions show clear co-rotating regions during this period, and the time-series extraction at spacecraft locations compares well with measurements made by the STEREO, Wind, and ACE spacecraft. This is the first time such clear structures have been revealed using this 3-D technique with EISCAT IPS data as input.     

Transneptunian Object Ephemeris Service (TNOEPH)

We present a web service called TNOEPH ( http://asteroid.lowell.edu/)for ephemeris uncertainty prediction and dynamical classification ofshort-arc trans\-neptunian objects (TNOs). User-supplied observations are transformed to a rigorous sky-plane uncertainty map using the technique of statistical orbital ranging. We show examples of thegrowth of ephemeris uncertainty with time, and give the probabilities ofdifferent dynamical classifications for a few short-arc TNOs.     

The Filament Disappearance of 7 May 1992 (the Ebi)

The 7 May 1992 filament disappearance in the low corona is analyzed. The cool and hot components of this event are studied, using H, soft X-ray and radio data. We first show the general effect of the disparition brusque (DB) on the life of the filament, which was a quiescent filament in the vicinity of an active region, and then give the history of the development of the 7 May event. The main stages of the event are: (i) the formation of hot arches spanning the cool filament; (ii) rise of the filament, with plasma ejection into the corona, in which we note some spreading of loops from the main body, with two distinct rising velocity phases of the H filament; (iii) formation of X-ray arches below the filament, the foot points of the arcades being two-ribbon H flare patches. The dynamics of H and X-rays features are given.