Source rates and ion recycling rates for Na and K in Mercury's atmosphere

The supply rates of Na and K to the atmosphere of Mercury by processes acting on the extreme surface—thermal vaporization, photon-stimulated desorption (PSD), and ion-sputtering—are limited by the rates at which atoms can be supplied to the extreme surface by diffusion from inside the regolith grains. Supply rates to the atmosphere are further regulated by ion retention and by gardening rates that supply new grains to the surface. We consider the limits on supply of sodium and potassium atoms to the atmosphere, and rates of photoion recycling to the surface. Thermal vaporization rates are severely limited by the ability of atoms to diffuse to the surface of the grain. Therefore, the diffusion-limited thermal vaporization rates on Mercury's surface are comparable to or less than the PSD rates. Ion sputtering is primarily due to highly ionized heavy ions, even though they represent a small fraction of the solar wind. We have shown that up to 60% of the Na photoions are deposited on the surface of Mercury. Ion recycling to the surface can have a long-term effect on the regolith abundance if an average recycling pattern persists such that more ions return to a particular area than are launched there. It is unknown whether the formation of latitude bands of >100% ion retention persist on average despite a rapidly changing magnetosphere. The total exospheric column of sodium observed at Mercury between 1997 to 2003 varied by a factor of 2-3 from perihelion to aphelion.     

Recovering the topology of the initial density fluctuations using the IRAS Point Source Catalogue Redshift Survey

We apply the reconstruction technique of Nusser & Dekel to the recently available Point Source Catalogue Redshift Survey (PSCz) in order to subtract the non-Gaussianities that are expected to develop in the mild non-linear regime of gravitational evolution. We study the evolution of isodensity contours defined using an adaptive smoothing algorithm, in order to minimize the problems derived from the non-commutativity of the smoothing operator and the time-evolution operator. We study the topology of these isodensity contours and concentrate on the evolution of the amplitude drop of the genus compared to a Gaussian field with an identical power spectrum, in order to quantify the level of phase-correlation present in the field. In order to test the method and to quantify the level of statistical uncertainty, we apply the method to a set of mock PSCz catalogues derived from the N -body simulations of two standard cold dark matter (CDM) models, kindly granted to us by the Virgo consortium. We find the method to be reliable in recovering the correct amplitude drops. When applied to PSCz, the level of phase correlations observed is very low on all scales ranging from 5 to 60  h ⁻¹ Mpc, providing support to the theory that structure originated from Gaussian initial conditions.     

The effect of massive binaries on stellar populations and supernova progenitors

We compare our latest single and binary stellar model results from the Cambridge stars code to several sets of observations. We examine four stellar population ratios: the number of blue to red supergiants, the number of Wolf–Rayet stars to O supergiants, the number of red supergiants to Wolf–Rayet stars and the relative number of Wolf–Rayet subtypes, WC to WN stars. These four ratios provide a quantitative measure of nuclear burning lifetimes and the importance of mass loss during various stages of the stars' lifetimes. In addition, we compare our models to the relative rate of Type Ib/c to Type II supernovae to measure the amount of mass lost over the entire lives of all stars. We find reasonable agreement between the observationally inferred values and our predicted values by mixing single and binary star populations. However, there is evidence that extra mass loss is required to improve the agreement further, to reduce the number of red supergiants and increase the number of Wolf–Rayet stars.     

Light-time computations for the BepiColombo Radio Science Experiment

The Radio Science Experiment is one of the on board experiments of the Mercury ESA mission BepiColombo that will be launched in 2014. The goals of the experiment are to determine the gravity field of Mercury and its rotation state, to determine the orbit of Mercury, to constrain the possible theories of gravitation (for example by determining the post-Newtonian parameters), to provide the spacecraft position for geodesy experiments and to contribute to planetary ephemerides improvement. This is possible thanks to a new technology which allows to reach great accuracies in the observables range and range rate; it is well known that a similar level of accuracy requires studying a suitable model taking into account numerous relativistic effects. In this paper we deal with the modelling of the space-time coordinate transformations needed for the light-time computations and the numerical methods adopted to avoid rounding-off errors in such computations.     

Frozen orbits at high eccentricity and inclination: application to Mercury orbiter

We hereby study the stability of a massless probe orbiting around an oblate central body (planet or planetary satellite) perturbed by a third body, assumed to lay in the equatorial plane (Sun or Jupiter for example) using a Hamiltonian formalism. We are able to determine, in the parameters space, the location of the frozen orbits, namely orbits whose orbital elements remain constant on average, to characterize their stability/unstability and to compute the periods of the equilibria. The proposed theory is general enough, to be applied to a wide range of probes around planet or natural planetary satellites. The BepiColombo mission is used to motivate our analysis and to provide specific numerical data to check our analytical results. Finally, we also bring to the light that the coefficient J ₂ is able to protect against the increasing of the eccentricity due to the Kozai-Lidov effect and the coefficient J ₃ determines a shift of the equilibria.     

Hipparcos trigonometric parallaxes and the distance scale for open star clusters

Hipparcos trigonometric parallaxes are used to estimate the distances to the maximum possible number of open star clusters (OSC); distance moduli are estimated for 45 clusters with maximum heliocentric distances of about 1000 pc. The latter value can serve as an estimate of the limit to which it still makes sense to use Hipparcos trigonometric parallaxes to determine the distances to small groups composed of 6–10 sufficiently bright stars. A systematic correction to the distance moduli of clusters from the homogeneous catalog of OSC parameters (Loktin et al. 1997, 2000) is estimated, which turns out to be independent of the cluster age.     

Cooperation with the SCOSTEP Project: Study of Travelling Interplanetary Phenomena (STIP)

The Flare Build-up Study (FBS) is primarily devoted to the study of various physical processes on the Sun prior to the occurrence of a solar flare. The relationship of these processes to the flare itself is then to be compared to similar, albeit smaller, processes in the magnetosopheric tail sometimes called the auroral flare. The Study of Travelling Interplanetary Phenomena (STIP) is devoted to specific studies of various phenomena from their inception on the Sun to their passage through the interplanetary medium. Some of these studies will be prior to and during both solar flare and magnetospheric substorm phenomena. Various scientific areas where the work of FBS and STIP would be mutually beneficial are discussed.     

Astro-WISE interfaces

From a simple text interface to a graphical user interfaces—Astro-WISE provides the user with a wide range of possibilities to interact with the information system according to the user’s tasks and use cases. We describe a general approach to the interfacing of a scientific information system. We use this approach to create a number of services, which allows the user to browse the data stored in the system, to process the data and to exchange the newly created images and catalogs with the users within the system and wider astronomical community. Reusability of interfaces and services is another important feature of our approach. It reduces the time and resources spent to interface other information systems created from Astro-WISE.     

Japanese 0.5 m AND 1.0 m telescopes for near-earth asteroid observations

To make detection andfollow-up observations of near-earth asteroids (NEOs), a new project tobuild 0.5 m and 1.0 m telescopes has been started with a support of theScience and Technology Agency in Japan. These are the first telescopesdesigned from its beginning to dedicate specifically to the NEOobservations and are expected to be one of the most efficient telescopesfor the NEO observations.It is expected to obtain several ten giga-bytedata per one clear night. Such large numbers of data are able to sharewith international groups. These sharing activities will contribute 1)for us to obtain data of asteroid with the lowest level of signal, and2) for those groups to study how to reduce astronomical data.     

SOLAR-A reformatted data files and observing log

All of the SOLAR-A telemetry data will be reformatted before distribution to the analysis computers and the various users. This paper gives an overview of the files which will be created and the format and organization which the files will use. The organization has been chosen to be efficient in space, to ease access to the data, and to allow for the data to be transportable to different machines. An observing log file will be created automatically using the reformatted data files as the input. It will be possible to perform searches with the observing log to list cases where instruments are in certain modes and/or seeing certain signal levels.After the launch the name of SOLAR-A has been changed to YOHKOH.     

汽车金融涌动升浪行情

在国家年初出台的汽车产业调整和振兴规划中,扶持以汽车金融公司为主的汽车信贷是重要一环。下半年有望出台实施细则,促进汽车消费信贷的发展。支持骨干汽车生产企业加快建立汽车金融公司,开展汽车消费信贷等业务,有望为车市继续繁荣提供新的动力。     

Evidence for the phi-dependent rotation-oscillation of the Sun (and for the driving mechanism of the asymmetric dynamo)

Longitude-dependent oscillations of the solar rotation are derived from the 27-day averages of the photospheric velocity data. Two pairs of prominent periods are obtained. Their harmonic means correspond to a semiannual variation and to the first harmonic of the latter. To explain the origin of the oscillation the corona and the interplanetary material are supposed to rotate parallel to the planetary plane with an inclination to the solar equator. The non-uniform shearing around the equator is assumed to result in oscillation with a period of half of a year.     

Digitization and Scientific Exploitation of the Italian and Vatican Astronomical Plate Archives

There is a widespread interest to digitize the precious information contained in the astronomical plate archives, both for the preservation of their content and for its fast distribution to all interested researchers in order to achieve their better scientific exploitation. This paper presents the first results of our large-scale project to digitize the archive of plates of the Italian Astronomical Observatories and of the Specola Vaticana. Similar systems, composed by commercial flat-bed retro-illuminated scanners plus dedicated personal computers and acquisition and analysis software, have been installed in all participating Institutes. Ad-hoc codes have been developed to acquire the data, to test the suitability of the machines to our scientific needs, and to reduce the digital data in order to extract the astrometric, photometric and spectroscopic content. Two more elements complete the overall project: the provision of high quality BVRI CCD sequences in selected fields with the Campo Imperatore telescopes, and the distribution of the digitized information to all interested researchers via the Web. The methods we have derived in the course of this project have been already applied successfully to plates taken by other Observatories, for instance at Byurakan and at Hamburg.     

Impact Excavation and the Search for Subsurface Life on Mars

Because of the ubiquity of subsurface microbial life on Earth, examination of the subsurface of Mars could provide an answer to the question of whether microorganisms exist or ever existed on that planet. Impact craters provide a natural mechanism for accessing the deep substrate of Mars and exploring its exobiological potential. Based on equations that relate impact crater diameters to excavation depth we estimate the observed crater diameters that are required to prospect to given depths in the martian subsurface and we relate these depths to observed microbiological phenomena in the terrestrial subsurface. Simple craters can be used to examine material to a depth of ∼270 m. Complex craters can be used to reach greater depths, with craters of diameters ≥300 km required to reach depths of 6 km or greater, which represent the limit of the terrestrial deep subsurface biosphere. Examination of the ejecta blankets of craters between 17.5 and 260 km in diameter would provide insights into whether there is an extant, or whether there is evidence of an extinct, deep subsurface microbiota between 500 and 5000 m prior to committing to large-scale drilling efforts. At depths <500 m some crater excavations are likely to be more important than others from an exobiological point of view. We discuss examples of impacts into putative intracrater paleolacustrine sediments and regions associated with hydrothermal activity. We compare these depths to the characteristics of subsurface life on Earth and the fossil microbiological record in terrestrial impact craters.     

All you ever wanted to know about optical long baseline stellar interferometry, but were too shy to ask your adviser

I try to present a small view of the properties and issues related to astronomical interferometry observations. I recall a bit of history of the technique, give some basic assessments to the principle of interferometry, and finally, describe physical processes and limitations that affect optical long baseline interferometry and which are, in general, very useful for everyday work. Therefore, this text is not intended to perform strong demonstrations and show accurate results, but rather to transmit the general “feeling” one needs to have to not be destabilised by the first contact to real world interferometry.     

A 3D hybrid simulation study of the electromagnetic field distributions in the lunar wake

A three-dimensional hybrid code is used to study the electromagnetic disturbances in the solar wind that arise due to the absorption effect of the Moon. Due to the nearly insulating nature of the Moon, interplanetary magnetic fields (IMFs) can move through the interior without hindrance. However, the near-vacuum created in the wake region due to the lunar absorption effect will lead to enhancement of the strength of the magnetic field by a factor of about 1.4 in the middle of the lunar wake and lead to depletions at two sides. The situations arising from different orientations of the interplanetary magnetic fields relative to the radial direction are compared. Asymmetries of the inward diffusions both along and perpendicular to the field lines are also observed. The electric field formed from the plasma convection could reach a magnitude of 0.2–0.8 mV/m at the border of the wake. The role of the electric field on the inward accelerations is important to the geometry of the lunar wake.     

SILENT: Spectrograph simulation and emulation tool

A software tool which was designed to compute basic optical parameters of spectrographs is presented. The idea is to find a first layout of the spectrograph by focusing on the science goal to which the instrument needs to be adapted. We focus on systems used in astrophysical instrumentation. These include classical, 3D and echelle spectrographs. The code also computes efficiencies of the specified systems, expected signal-to-noise ratios, layout of the spectral orders on the detector, etc. Furthermore, a complete image seen by the detector can be simulated. This artificial data are used to compare the performance of different designs and to test data reduction pipelines, before the system is being physically build. Some additional tools are implemented to characterise special optical devices, for example the telescope-spectrograph-interface and to support the design process. Hence, SILENT is a pre-design tool to determine the required optical paraxial parameters of the system to meet the science application.     

Meteoroid streams at Mars: possibilities and implications

In order to assess the possibility of meteoroid streams detectable from the surface of Mars as meteor showers we have derived minimum distances and associated velocities for a large sample of small body orbits relative to the orbits of Mars and the Earth. The population ratio for objects approaching to within 0.2 AU of these two planets is found to be approximately 2:1. The smaller relative velocities in the case of Mars appears to be the main impediment to the detection of meteors in the upper atmosphere of that planet. We identify five bodies, including the unusual object (5335) Damocles and periodic comet 1P/Halley, with relative orbital parameters most suitable to produce prominent meteor showers. We identify specific epochs at which showers related to these bodies are expected to occur. An overview of possible detection methods taking into account the unique characteristics of the Martian environment is presented. We pay particular attention on the effects of such streams on the dust rings believed to be present around Mars.     

Observations of baily's beads from near the Northern limit of the total solar eclipse of June 20, 1974

Baily beads were observed from near the northern limit of totality during the eclipse of June 20, 1974; no attempt of identification was made at the time of observation. The observations were analysed to identify the features of the lunar profile which gave rise to the beads observed. They were then analysed to derive corrections to the relative positions of the Sun and Moon, and to investigate certain features of the lunar profile.     

判定光变周期的一种方法

Jurkevich方法通常用来发现光变曲线的周期 ,并且根据V2 m 极小值的大小来验证所发现的光变周期可靠性。但是 ,这种验证方法又带有一定的不确定性 ,最佳的方法是把所发现的周期与观测光变曲线拟合 ,得出每一个周期的振幅 ,以振幅大小来验证所发现的光变周期的可靠性。将此方法用于OJ2 87的历史光变曲线 ,得到其最主要的周期为 11.9年 ,与其它结果相符合。